This article was downloaded by: [Van Pelt and Opie Library] On: 16 October 2014, At: 02:52 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Veterinary Quarterly Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tveq20
Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration a
a
M. Dagorn , P. Guillot & P. Sanders
a
a
Centre National d'Etudes Vétérinaires et Alimentaires Laboratoire Des Médicaments Vétérinaires , Ministère de l'Agriculture et de la Forêt CNEVA , La Haute‐Marche, Javene, Fougeres, 35133, France Published online: 01 Nov 2011.
To cite this article: M. Dagorn , P. Guillot & P. Sanders (1990) Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration, Veterinary Quarterly, 12:3, 166-174, DOI: 10.1080/01652176.1990.9694262 To link to this article: http://dx.doi.org/10.1080/01652176.1990.9694262
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
M. Dagorn, P. Guillot, and P. Sanders'
SUMMARY. The pharmacokinetics of chloramphenicol were studied in sheep after 3 single intravenous (iv), intramuscular (im) and subcutaneous (sc) administrations (30 mg/kg). The two extravascular routes were studied during a crossover trial for a bioequivalence test. After iv and sc administrations, the plasma-concentration time graphs were characteristic of a twocompartment model, and after Im administration it was chracteristic of a monocompartment model. The two routes of absorption were not bioequivalent. Using the kinetic values, multidose regimens to maintain the therapeutic chloramphenicol blood level (5 pg/m1) were proposed: 60 mg/kg every 12 hours for 72 hours for the Im administration and 45 mg/kg administered subsutaneously according to the same regimen. A study of the chloramphenicol residues in tissues was carried out. Chlorgmphenicol residues remained at the injection site, and 400 hours would be necessary to obtain the level of 10
pg/kg. Determination of the creatinine phosphokinase serum values showed that the subcutaneous route induced less damage to muscle than the intramuscular route. INTRODUCTION
Chloramphenicol has been used for more than 40 years in both human and veterinary medicine (2) for the treatment of many infections, especially those caused by such Gram-negative bacteria as Escherichia Coli and Salmonella sp. To be therapeutically effective, a plasma chloramphenicol concentration of 5 mcg/ml
is generally considered necessary (10). Due to its side-effects (aplasic anaemia) and the increasing number of resistant strains, a more proper and selective usage is necessary. Besides, it is necessary to give an assurance that residues in food are safe for sensitive subjects. The EEC Committee for Veterinary Medicinal Products recommends a maximum of 10 mcg/kg in animal tissues destined for human consumption (6). In relation to Good Veterinary Practice, a pharmacokinetic and drug-residue study
was performed in sheep after the intramuscular (Im) and subcutaneous (sc) administration of 30 mg/kg chloramphenicol. The study's objective was to develop a better dosage regimen for the drug in sheep.
Furthermore, as local irritation and extensive tissue damage follOwing im administration of antibiotics have already been described (5), the creatinine phospho-kinase (CPK) plasma concentrations were monitored to determine whether the use of the subcutaneous route induced less damage to muscle than the intramuscular route. I
Ministère de l'Agriculture et de la Foret CNEVA, Centre National d'Etudes Vétérinaires et Alimentaires Laboratoire Des Medicaments Vétérinaires, La Haute-Marche, Javene, 35133 Fougeres, France.
166
THE VETERINARY QUARTERLY, VOL. 12, No. 3, Jun' 1990
MATERIALS AND METHODS
Experiment
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
A commercial preparation of chloramphenicol base, 30 g/100 ml in a vehicle containing dimethyl sulphoxide and a glycerol compound, was used (Cloralon, batch 857, Gifavet). Studies were conducted on 17 ewes (Rouge de L'Ouest) weighing 54.20 ± 6.40 kg, divided into two groups. The first group six animals received a single dose of 30 mg/kg chloramphenicol base as an iv bolus injection. One week later, the usif and sc routes were tested using a random crossover trial design with a two-week `washout' interval. A single administration of 30 mg/kg chloramphenicol base was given by each route. The sc injections were administered in the flank; intramuscular injections were performed deep into the gluteal muscle. All animals were slaughtered seven days after the last administration. The second group 11 animals divided into four groups three with three sheep and the
fourth with two received a single dose of 30 mg/kg chloramphenicol base by the intramuscular route. Animals were slaughtered 4, 10 and 24 hours and 14 days after treatment. In both groups, blood samples were collected from the jugular vein
after 0, 2, 4, 8, 15, 30 and 45 minutes and 1, 2, 4, 6, 8, 12, 24 and 48 hours for the iv administration, after 0, 15, 30 and 45 minutes and 1, 1.5, 2, 2.5, 4. 5. 7. 12. 15. 24. 48 and 72 hours for the other routes of administration. Muscles, livers, kidneys and injection sites were collected after slaughtering. The concentrations of chloramphenicol in samples were determined by HPLC according to the method previously described (7, 1 The sensitivity of the method was 10 ng/ml for plasma and 2 ng/g for tissues. Serum CPK values were determined in samples taken 0, 4, 10, 12, 48, 96, 120 and 144 hours
post injection by automatic micromethod (Tests Enzyline CK NAC optimise 20 6 1145, Biomerieux, France). Pharmacokinetic analysis
Bi- and triexponential equations were successively fitted to the chloramphenicol plasma concentrations following iv, Itsif, and sc administration by means of the least squares method (11).
The programme was applied to fit the entire time curve of drug concentration in the plasma samples collected. The model equation with minimum Akaike's information criterion (AIC) was chosen as the best representation for describing the chloramphenicol disposition. Initial estimates of the parameters were determined by graphical analysis (11). Thereafter, parameters describing absorption and bioavailability were statistically compared by Student's t test for paired observations to examine the bioequivalence of the two extravascular routes. RESULTS
Plasma data
Mean chloramphenicol concentrations in the plasma are plotted for each administration route in Fig. 1. Table 1 presents the calculated pharmacokinetic parameters. Two minutes after iv administration of 30 mg/kg of chloramphenicol to sheep, plasma concentrations were 90.24 ± 17.50 mcg/ml, and then declined to the limit of sensitivity within six hours. These data were best described by a biexponentiel equation, characteristic of a two-compartment model: C = A 6-.0 + B e (-B t) where A and B are mathematical coefficients, a is the fasted disposition rate constant (h-I) and /3 is the slowest disposition rate constant (h-I). Chloramphenicol distribution from the central to the peripheral compartment (K12: 6.68 ± 0.23 h-I) was similar to the back diffusion (K21: 5.30 ± 0.06 h-I). THE VETERINARY QUARTERI Y. VOL.
12, No. 3, JULY 1990
167
100
-7..
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
10
.1
_ 0
24
12
48
36
time
60
72
(h)
Fig. I. Semilogarithmic plot of plasma chloramphenicol concentrations (mcg/ml) vs. time (h) after intravenous, intramuscular and subcutaneous administration of chloramphenicol (30 mg/kg) in six sheep. MA : intravenous -eoe- : intramuscular -eee- : subcutaneous Vertical lines represent the standard deviation.
Table I. Phamacokinetic parameters of chloramphenicol with different routes of administration (mean values ±). Dosage (mg/kg) Administration route number of sheep
30 i.v.
30
30
s.c.
i.m.
6
6
6
A
mcg/ml
69.36 ± 11.06
a
h -I
B
mcg/m1
13.05 ± 0.24 40.83 ± 1.14
T I/2/3
h -1 h h
AUC
mcg.h/m1
K21
h -1
Yo Kel
mcg/m1
13
T I/2a
K12
h h
Vc
I/kg
Vd
1/kg
CI
ml/kg/mn
t I/2Ka
h h
Ka
MRT MAT
168
h
h
-1 -1
0.399 ± 0.005 0.050 ± 0.011 1.702 ± 0.0192
108.40 ± 5.46 5.303 ± 0.062
5.17 0.27 2.18 0.038 1.60 17.93
65.19
± 1.85 ± 0.16 ± 0.25 ± 0.001 ± 0.28 ± 0.25 ± 3.5
21.52 ± 1.84 1.13 ± 0.04
0.249 ± 0.003 0.51 ± 0.02 2.71 ± 0.03 84.34 ± 5.46
0.1373 ± 0.0067
110.19 ± 11.37 0.990 ± 0.018 6.667 ± 0.232 0.289 ± 0.034 0.691 ± 0.019
4.66 ± 0.222 0.18 0.45
-1 -1
2.382 ± 0.152
- 1.43* - 3.71*
19.076 ± 0.227 16.694 ± 0.577
0.36 1.07
- 1.09* - 2.33*
5.108 ± 0.247 2.727 ± 0.262
THE VETERINARY QUARTERLY, Vol.. 12, No. 3, JULY 1990
Intercept of the distribution phase for iv and sc administrations F x D /V for Inn administration Slope of the distribution phase a: Intercept of the elimination phase B: Slope of the elimination phase /3: Concentration at t =0 Yo: area under the curve AUC: Central distribution volume Vc: Dose/AUC.P Vd,a: Clearance CI: 0.693/a T1/2 a: 0.693/0 T1/2 /3: K12= a + fl - K21 - Kel, K21 = (Aa + B/3)/(A + B), Kel = a/3/K2I Mean Residence Time MRT: Mean Absorption Time MAT: Half-time of absorption t1/2: Apparent first-order absorption rate constant Ka: range of values *: A:
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
A=
The apparent volume of the central compartment (Vc) ranged from 0.208 to 0.430 1/kg and the volume of distribution (Vd) from 0.602 to 0.734 1/kg. After a single Inn administration of 30 mg/kg of chloramphenicol (Fig. 1), the maximum plasma concentrations (13.90 ± 0.85 mcg/m1) were obtained within 1.63
± 0.16 hours. The best-fitted representation was a biexponential equation, characteristic of a mono-compartment model: C = (F x D/V) (6-Bt) -1- e(-Ka t)) with F the fraction of dose D absorbed, V the volume of distribution (1), B the slowest disposition-rate constant (h-I), and Ka the apparent first order absorptionrate constant (h-I). The absorption was characterised by a 0/2 Ka ranging from 0.30 to 1.09 h. The mean apparent bioavailability, given by the area under the plasma-concentration time curve (AUC) was 83.01 ± 3.20%. The terminal slope B of the profile was 0.249 ± 0.003 h-I and did not differ significantly from that of the iv curve (t = 1.798 - p < 0.05). In the case of the sc administration, the disposition of chloramphenicol was best described by the following triexponential equation: C = A e(-at) + B e(-t) - (A + B) e(-Ka t).
After a lag time of 0.77 to 3.46 hours, the plasma concentration rose only to 3.10
± 0.14 mcg/ml and then declined to 0.110 ± 0.05 mcg/ml three days after the administration. The mean apparent bioavailability was 65.19%. The terminal slope B differed significantly from that obtained after iv administration (t = 14.260, p < 0.05). The disposition of chloramphenicol in sheep was described by two different models
according to the extravascular route studied: a mono-compartment model in the case of Inn and a two-compartment model for the sc route. Statistical analysis of Cmax, Tina AUC and MRT calculated for the two routes demonstrated significant differences between the Inn and sc parameters. It is important to note that for the formulation tested, the highest plasma level obtained after Inn administration (13.90 ± 0.85 mcg/m1) was higher than the therapeutic concentration but decreased to 4.16 ± 3.53 mcg/ml within seven hours. However, a single sc injection of 30 mg/kg did not achieve the minimum effective leven (Cmax = 3.10 ± 0.14 mcg/m1). THE VETERINARY QUARTERLY, VOL.
12, No. 3, JULY 1990
169
Tissue data
The tissue concentrations of chloramphenicol were evaluated from samples collected in the second experimental group (Fig. 2). The elimination rate constant
was calculated by linear regression for each tissue (Table 2). The mean time required to reach a level of 10 mcg/kg in different tissues was calculated from the kinetic equation. 6
Mumh
5
1
Liver
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
4 K
3
a
K M.
fo,
-de IS
2
Pawn]
0 4h
24h
10 h
336 h
rme
Fig. 2. Tissue residues of chloramphenicol after a single intramuscular administration of chloramphenicol (30 mg/kg). K.C. : Kidney Cortex K.M.: Kidney Medulla I.S.: Injection Site Table 2.
Elimination of chloramphenicol from sheep tissues after a single irvi administration of 30
mg/kg. Tissues
equation
calculated time in hours , to reach 10 mcg/kg
muscle liver kidney
19983.73 e (- 0.214 0
36 - (27-49)* 6 - (1-44)
Inj. site
cortex medulla im
16.21 e (- 0.832 t) 94.20 e (-0.11000 1537.56 e (- "80 248280.00 e (- 0.025 0
21
37
400
- (3-91)
-
(25-60)
- (230-680)
* = confidence region of 95% in sheep population.
The present study shows that chloramphenicol residues remained at the injection site and that 400 hours i.e. 16.66 days should be necessary to obtain the level of 10 mcg/kg at the site, whereas, for example, 6 hours are sufficient to reach this level in the liver. . Plasma creatine phospho-kinase Plasma creatine phospho-kinase levels following subcutaneous and intramuscular administration of chloramphenicol are given in Table 3. 170
THE VETERINARY QUARTERLY, VOL. 12,
No. 3, JULY 1990
Table 3. Plasma serum ccreatine phospho-kinase following the administrations of chloramphenicol (mU/m1).
intramuscular route (n = 8)
subcutaneous route (n = 6)
Time post injection
42.48 ± 18.1 1151.12 ± 556.04 473.16 ± 220.04 256.91 ± 171.79 151.73 ± 74.59 53.04 ± 18.63 26.63 ± 2.57 34.31 ± 36.06
35.85 ± 19.02
0 4
115.21 ± 91.98
45.69 ± 58.47 41.42 ± 39.15 29.79 ± 7.50 31.93 ± 17.33
12
24 48 72 96
18.57 23.92
144
± 1.77 ± 8.44
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
Values are means ± standard deviation.
100
10
1
0
1
24
72
48
Time
96
120
(h1
Fig. 3. Semilogarithmic plot of plasma chloramphenicol concentrations (mcg/ml) vs. time (h) after simulation of intramuscular and subcutaneous chloramphenicol treatment with 6 injections at 12-hour intervals. Therapeutic chloramphenicol level (5 mcg/m1): Mean plasma data after a single administration of 30 mg/kg by
-- -
- intramuscular route: - subcutaneous route:
a AA
Simulation of a treatment with 6 injections of Chloralon at 12-hour intervals.
- Intramuscular simulation - 60 mg/kg/12 - Subcutaneous simulation - 45 mg/kg/I2
h. h: ...........
DISCUSSION
The curve obtained after iv injection was characteristic of a two-compartment model. In sheep, chloramphenicol disposition is described by the same model as in cattle (1, 11). The previous works on sheep (4, 12) have not described the kinetics
of chloramphenicol disappearance from plasma after iv administration. In this study, the following pharmacokinetic parameters were established: plasma halflife 0/2 B = 1.7 hour, volumes of distribution Vd = 0.691 ± 0.019 1/kg, Vc = 0.289
± 0.034 1/kg and clearance CI = 4.66 ± 0.22 ml/min. Amongst the different THE VETERINARY QUARTERLY, VOL. 12, No. 3, JULY 1990
171
pharmacokinetics of chloramphenicol studied in domestic animals, the 0/2 B
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
determined was of the same order as in swine (1.3 h) and goats (2 h) (3). In cattle (11), these values are higher and range from 2.50 to 5.33 hours, probably due to a lower metabolic rate (13). Values for the apparent volume of distribution Vd are only twice that of the central volume Vc; they are close to those found in cattle (Vd = 0.859 ± 0.1241/kg, Vc = 0.351 ± 0.1161/kg) (11). In sheep, chloramphenicol is well distributed.
After im and sc administrations, the pharmacokinetics of chloramphenicol in sheep were described by two different models: a mono-compartment model after im and a two-compartment model after sc. The slopes of the terminal phases were quite different. The rate constant of elimination B after IN4 administration (0.249 ± 0.124 h-I) is close to that when the product is given by the iv route. After sc administration, this parameter is much lower (0.0382 ± 0.0005 h-I). This difference was a typical case of 'flip-flop', i.e., the final slope of the curve for the sc route agreed with the absorption phase. The absorption rate after sc injection is slower than that after im administration. The slow rate observed when the product is injected sc has already been described and is acknowledged for other drugs (8). The fraction of dose absorbed (F), was respectively, 83.01% and 61.19% after In4 and sc treatments. This difference in absorption explains partially why Cma, is much higher after im than after sc injection. When, for two different routes, the rates and extents of absorption are
similar, such routes are admitted to be bioequivalent. In this case, as these parameters are quite different, the two routes of absorption are not bioequivalent. For bacteriostatic antibiotics, the time during which the blood level is in excess or equal to the effective concentration for specific bacteria is very important. Two or three parenteral doses per day, over several days, are often required to achieve the claimed minimum therapeutic blood concentration generally for 75% of the
72 hours of treatment. The simulation of six administrations of 30 mg/kg of chloramphenicol given every 12 hours by each route showed that the therapeutic blood concentration (5 mcg/m1) would be maintained only for 55% and 29.2%
of the treatment time after Im and sc administration, respectively. Adequate therapeutic conditions to obtain the required level for 75% of the treatment period
were obtained with im administration of the tested product Cloralon, by a simulation of 60 mg per kg body weight every 12 hours for 72 hours, while a 45 mg/kg dose administered subcutaneously according to the same regimen was sufficient to be effective under conditions described above (Fig. 3). Our findings are in good agreement with the experiment conducted on ewes infected with a colony of S. aureus (14). After a single im injection of 50 mg/kg of chloramphenicol, the drug concentration determined using a colorimetric method remained relatively constant (8 mcg/m1) from 4.50 to 12.50 hours. It is important to realise that the solubility and absorption of chloramphenicol
depend on both on formulation and on mode of administration, i.e., per os or per iv, im or sc injection. Chloramphenicol is commercially available as a free base (in our product) or as a succinate, palmitate, glycinate or undecylenate ester. It is important to select the appropriate form of the drug for IN4 injection. A dose of 50 mg/kg by IN4 has been proposed for sheep (2). Under our experimental conditions, after a single intramuscular injection of 30 mg/kg of chloramphenicol to sheep, the persistence in edible tissues (muscle, liver, kidney) was different according to the nature of the tissue. Within two days the residues in the following tested tissues, liver, kidney (cortex and medulla) and
muscle (except the injection-site muscle), had fallen below the 10 mcg of chloramphenicol tolerated per kg. However, at the injection site, intramuscular 172
THE VETERINARY QUARTERLY, VOL 12, No. 3, JULY 1990
deposits were higher and about 17 days would be necessary to attain the tolerated value. This shows the weak bioavailability of chloramphenicol when administered intramuscularly (9). The present results on plasma CPK levels shows that the tolerance appeared to
be better when the product was injected by the subcutaneous route. After subcutaneous administration, the CPK serum enzyme values rose slightly to 3.2 times the pretrial levels, whereas after intramuscular injection they increased almost 27-fold. The CPK level fell to the initial level within 96 hours. Subcutaneous tissue cells are poor in CPK while muscle cells are rich in this enzyme. The small
increase in CPK after subcutaneous administration does not exclude local irritation but indicates less damage to the muscles. CONCLUSION
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
The pharmacokinetics of chloramphenicol in sheep after IN4 and sc administrations
were described by two different models: a mono-compartment model after irvi, and a two-compartment model after sc. The slopes of the terminal phases of IN4 and sc curves and the rates and extents of absorption are quire different, implying that the two routes of absorption are not bioequivalent. Adequate therapeutic conditions to obtain a 5 mcg/ml chloramphenicol blood level during 75% of the treatment were obtained for im administrations of the tested product, Cloralon by a simulation of 60 mg per kg body weight 12 hours for 72 hours, while a 45 mg/kg dose administered subcutaneously according to the same regimen was sufficient to maintain an effective level under the same conditions. The study of the chloramphenicol tissue distribution after im administration showed that intramuscular deposites at the injection site were higher than in other tissue and about 17 days would be necessary for the chloramphenicol to fall to the tolerated level (10 mcg/kg). ACKNOWLEDGEMENTS
The authors thank Mrs J. Manceau and Mr B. Delepine for their technical assistance. REFERENCES I. Burrows GE, Barto PB, Martin B, and Tripp ML. Comparative pharmacokinetics of antibiotics 2. 3.
4.
in newborn calves: Chloramphenicol, lincomycin, and tylosin. Am J Vet Res 1983; 44: 1053-7. Davis LL. Chloramphenicol therapy in large animals. J Am Vet Med Assoc 1981; 178: 309-10.
Davis LE, Neff CA, Baggot JD, and Powers TE. Pharmacokinetics of chloramphenicol in domestic animals. Am J Vet Res 1972; 33: 2259-66. De Corte-Bactcn K, Debackere M. Chloramphenicol plasma levels in horses, cattle and sheep after oral and intramuscular route. Zbl Vet Med (A) 1975; 22: 704-12.
5. De Laistre Banting A and Fanneau de la Horie GC. Subcutaneous and intramuscular injection of oxytetracycline in calves: comparison of serum concentration and local tolerance. J Vet Pharmacol Therap 1987; 10: 184-6. 6.
In FAO/WHO thirty-second report. Comments on residues of specific veterinary drugs.
Antimicrobial agents: chloramphcnicol. 1988; 16. 7. Guillot P and Mourot D. Chloramphenicol and oxytetracycline residues in milk and tissues from cows and bullocks treated with an injectable formulation. Food Additives and Contaminants, 1989 (in press). 8. MacDiarmid SC. The absorption of drugs from subcutaneous and intramuscular injection sites. Veterinary Bulletin 1983; 53: 9-23.
9. Nouws JFM and Ziv G. Serum chloramphenicol levels and the intramuscular bioavability of several parenteral formulations of chloramphenicol in ruminants. The Veterinary Quarterly 1979; 10.
1: 47-58. Nouws JFM, Vree TB, Holtkamp J, Baakman M, Driessens F, and Guelen PJM. Pharmacokinetic,
residue and irritation aspects of chloramphenicol sodium succinate and a chloramphenicol base formulation following intramuscular administration to ruminants. The Veterinary Quarterly 1986; 8: 224-32. THE VETERINARY QUARTERLY. VOL. 12, No. 3, JULY 1990
173
11. Sanders P, Guillot P. and Mourot D, Pharmacokinetics ofa long-acting formulation administered by intramuscular and subcutaneous routes in cattle. J Vet Pharmacol Therap 1988; 11: 183-90. 12. Theodorides VJ, Dicuello CJ, Guarini JR, and Pagano JF. Serum concentrations of chloramphenicol after intraruminal and intra-abomasal administration in sheep. Am J Vet Res 1968; 29: 643-5.
13. Van Miert ASJPAM, Bogaert MG, and Debackere M. Comparative Veterinary Pharmacology, Toxicology and Therapy. MTP Press, Lancaster 1986; 489-500. 14. Ziv G, Bogin E, and Sulman FG. Blood and milk in normal and mastitic cows and ewes after intramuscular administration of chloramphenicol and chloramphenicol sodium succinate. Zbl Vet
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
(A) 1973; 20: 801-11.
174
THE VETERINARY QUARTERLY. VOL 12, No. 3, JULY 1990
Veterinary Quarterly Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tveq20
Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration a
a
M. Dagorn , P. Guillot & P. Sanders
a
a
Centre National d'Etudes Vétérinaires et Alimentaires Laboratoire Des Médicaments Vétérinaires , Ministère de l'Agriculture et de la Forêt CNEVA , La Haute‐Marche, Javene, Fougeres, 35133, France Published online: 01 Nov 2011.
To cite this article: M. Dagorn , P. Guillot & P. Sanders (1990) Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration, Veterinary Quarterly, 12:3, 166-174, DOI: 10.1080/01652176.1990.9694262 To link to this article: http://dx.doi.org/10.1080/01652176.1990.9694262
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Pharmacokinetics of chloramphenicol in sheep after intravenous, intramuscular and subcutaneous administration
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
M. Dagorn, P. Guillot, and P. Sanders'
SUMMARY. The pharmacokinetics of chloramphenicol were studied in sheep after 3 single intravenous (iv), intramuscular (im) and subcutaneous (sc) administrations (30 mg/kg). The two extravascular routes were studied during a crossover trial for a bioequivalence test. After iv and sc administrations, the plasma-concentration time graphs were characteristic of a twocompartment model, and after Im administration it was chracteristic of a monocompartment model. The two routes of absorption were not bioequivalent. Using the kinetic values, multidose regimens to maintain the therapeutic chloramphenicol blood level (5 pg/m1) were proposed: 60 mg/kg every 12 hours for 72 hours for the Im administration and 45 mg/kg administered subsutaneously according to the same regimen. A study of the chloramphenicol residues in tissues was carried out. Chlorgmphenicol residues remained at the injection site, and 400 hours would be necessary to obtain the level of 10
pg/kg. Determination of the creatinine phosphokinase serum values showed that the subcutaneous route induced less damage to muscle than the intramuscular route. INTRODUCTION
Chloramphenicol has been used for more than 40 years in both human and veterinary medicine (2) for the treatment of many infections, especially those caused by such Gram-negative bacteria as Escherichia Coli and Salmonella sp. To be therapeutically effective, a plasma chloramphenicol concentration of 5 mcg/ml
is generally considered necessary (10). Due to its side-effects (aplasic anaemia) and the increasing number of resistant strains, a more proper and selective usage is necessary. Besides, it is necessary to give an assurance that residues in food are safe for sensitive subjects. The EEC Committee for Veterinary Medicinal Products recommends a maximum of 10 mcg/kg in animal tissues destined for human consumption (6). In relation to Good Veterinary Practice, a pharmacokinetic and drug-residue study
was performed in sheep after the intramuscular (Im) and subcutaneous (sc) administration of 30 mg/kg chloramphenicol. The study's objective was to develop a better dosage regimen for the drug in sheep.
Furthermore, as local irritation and extensive tissue damage follOwing im administration of antibiotics have already been described (5), the creatinine phospho-kinase (CPK) plasma concentrations were monitored to determine whether the use of the subcutaneous route induced less damage to muscle than the intramuscular route. I
Ministère de l'Agriculture et de la Foret CNEVA, Centre National d'Etudes Vétérinaires et Alimentaires Laboratoire Des Medicaments Vétérinaires, La Haute-Marche, Javene, 35133 Fougeres, France.
166
THE VETERINARY QUARTERLY, VOL. 12, No. 3, Jun' 1990
MATERIALS AND METHODS
Experiment
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
A commercial preparation of chloramphenicol base, 30 g/100 ml in a vehicle containing dimethyl sulphoxide and a glycerol compound, was used (Cloralon, batch 857, Gifavet). Studies were conducted on 17 ewes (Rouge de L'Ouest) weighing 54.20 ± 6.40 kg, divided into two groups. The first group six animals received a single dose of 30 mg/kg chloramphenicol base as an iv bolus injection. One week later, the usif and sc routes were tested using a random crossover trial design with a two-week `washout' interval. A single administration of 30 mg/kg chloramphenicol base was given by each route. The sc injections were administered in the flank; intramuscular injections were performed deep into the gluteal muscle. All animals were slaughtered seven days after the last administration. The second group 11 animals divided into four groups three with three sheep and the
fourth with two received a single dose of 30 mg/kg chloramphenicol base by the intramuscular route. Animals were slaughtered 4, 10 and 24 hours and 14 days after treatment. In both groups, blood samples were collected from the jugular vein
after 0, 2, 4, 8, 15, 30 and 45 minutes and 1, 2, 4, 6, 8, 12, 24 and 48 hours for the iv administration, after 0, 15, 30 and 45 minutes and 1, 1.5, 2, 2.5, 4. 5. 7. 12. 15. 24. 48 and 72 hours for the other routes of administration. Muscles, livers, kidneys and injection sites were collected after slaughtering. The concentrations of chloramphenicol in samples were determined by HPLC according to the method previously described (7, 1 The sensitivity of the method was 10 ng/ml for plasma and 2 ng/g for tissues. Serum CPK values were determined in samples taken 0, 4, 10, 12, 48, 96, 120 and 144 hours
post injection by automatic micromethod (Tests Enzyline CK NAC optimise 20 6 1145, Biomerieux, France). Pharmacokinetic analysis
Bi- and triexponential equations were successively fitted to the chloramphenicol plasma concentrations following iv, Itsif, and sc administration by means of the least squares method (11).
The programme was applied to fit the entire time curve of drug concentration in the plasma samples collected. The model equation with minimum Akaike's information criterion (AIC) was chosen as the best representation for describing the chloramphenicol disposition. Initial estimates of the parameters were determined by graphical analysis (11). Thereafter, parameters describing absorption and bioavailability were statistically compared by Student's t test for paired observations to examine the bioequivalence of the two extravascular routes. RESULTS
Plasma data
Mean chloramphenicol concentrations in the plasma are plotted for each administration route in Fig. 1. Table 1 presents the calculated pharmacokinetic parameters. Two minutes after iv administration of 30 mg/kg of chloramphenicol to sheep, plasma concentrations were 90.24 ± 17.50 mcg/ml, and then declined to the limit of sensitivity within six hours. These data were best described by a biexponentiel equation, characteristic of a two-compartment model: C = A 6-.0 + B e (-B t) where A and B are mathematical coefficients, a is the fasted disposition rate constant (h-I) and /3 is the slowest disposition rate constant (h-I). Chloramphenicol distribution from the central to the peripheral compartment (K12: 6.68 ± 0.23 h-I) was similar to the back diffusion (K21: 5.30 ± 0.06 h-I). THE VETERINARY QUARTERI Y. VOL.
12, No. 3, JULY 1990
167
100
-7..
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
10
.1
_ 0
24
12
48
36
time
60
72
(h)
Fig. I. Semilogarithmic plot of plasma chloramphenicol concentrations (mcg/ml) vs. time (h) after intravenous, intramuscular and subcutaneous administration of chloramphenicol (30 mg/kg) in six sheep. MA : intravenous -eoe- : intramuscular -eee- : subcutaneous Vertical lines represent the standard deviation.
Table I. Phamacokinetic parameters of chloramphenicol with different routes of administration (mean values ±). Dosage (mg/kg) Administration route number of sheep
30 i.v.
30
30
s.c.
i.m.
6
6
6
A
mcg/ml
69.36 ± 11.06
a
h -I
B
mcg/m1
13.05 ± 0.24 40.83 ± 1.14
T I/2/3
h -1 h h
AUC
mcg.h/m1
K21
h -1
Yo Kel
mcg/m1
13
T I/2a
K12
h h
Vc
I/kg
Vd
1/kg
CI
ml/kg/mn
t I/2Ka
h h
Ka
MRT MAT
168
h
h
-1 -1
0.399 ± 0.005 0.050 ± 0.011 1.702 ± 0.0192
108.40 ± 5.46 5.303 ± 0.062
5.17 0.27 2.18 0.038 1.60 17.93
65.19
± 1.85 ± 0.16 ± 0.25 ± 0.001 ± 0.28 ± 0.25 ± 3.5
21.52 ± 1.84 1.13 ± 0.04
0.249 ± 0.003 0.51 ± 0.02 2.71 ± 0.03 84.34 ± 5.46
0.1373 ± 0.0067
110.19 ± 11.37 0.990 ± 0.018 6.667 ± 0.232 0.289 ± 0.034 0.691 ± 0.019
4.66 ± 0.222 0.18 0.45
-1 -1
2.382 ± 0.152
- 1.43* - 3.71*
19.076 ± 0.227 16.694 ± 0.577
0.36 1.07
- 1.09* - 2.33*
5.108 ± 0.247 2.727 ± 0.262
THE VETERINARY QUARTERLY, Vol.. 12, No. 3, JULY 1990
Intercept of the distribution phase for iv and sc administrations F x D /V for Inn administration Slope of the distribution phase a: Intercept of the elimination phase B: Slope of the elimination phase /3: Concentration at t =0 Yo: area under the curve AUC: Central distribution volume Vc: Dose/AUC.P Vd,a: Clearance CI: 0.693/a T1/2 a: 0.693/0 T1/2 /3: K12= a + fl - K21 - Kel, K21 = (Aa + B/3)/(A + B), Kel = a/3/K2I Mean Residence Time MRT: Mean Absorption Time MAT: Half-time of absorption t1/2: Apparent first-order absorption rate constant Ka: range of values *: A:
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
A=
The apparent volume of the central compartment (Vc) ranged from 0.208 to 0.430 1/kg and the volume of distribution (Vd) from 0.602 to 0.734 1/kg. After a single Inn administration of 30 mg/kg of chloramphenicol (Fig. 1), the maximum plasma concentrations (13.90 ± 0.85 mcg/m1) were obtained within 1.63
± 0.16 hours. The best-fitted representation was a biexponential equation, characteristic of a mono-compartment model: C = (F x D/V) (6-Bt) -1- e(-Ka t)) with F the fraction of dose D absorbed, V the volume of distribution (1), B the slowest disposition-rate constant (h-I), and Ka the apparent first order absorptionrate constant (h-I). The absorption was characterised by a 0/2 Ka ranging from 0.30 to 1.09 h. The mean apparent bioavailability, given by the area under the plasma-concentration time curve (AUC) was 83.01 ± 3.20%. The terminal slope B of the profile was 0.249 ± 0.003 h-I and did not differ significantly from that of the iv curve (t = 1.798 - p < 0.05). In the case of the sc administration, the disposition of chloramphenicol was best described by the following triexponential equation: C = A e(-at) + B e(-t) - (A + B) e(-Ka t).
After a lag time of 0.77 to 3.46 hours, the plasma concentration rose only to 3.10
± 0.14 mcg/ml and then declined to 0.110 ± 0.05 mcg/ml three days after the administration. The mean apparent bioavailability was 65.19%. The terminal slope B differed significantly from that obtained after iv administration (t = 14.260, p < 0.05). The disposition of chloramphenicol in sheep was described by two different models
according to the extravascular route studied: a mono-compartment model in the case of Inn and a two-compartment model for the sc route. Statistical analysis of Cmax, Tina AUC and MRT calculated for the two routes demonstrated significant differences between the Inn and sc parameters. It is important to note that for the formulation tested, the highest plasma level obtained after Inn administration (13.90 ± 0.85 mcg/m1) was higher than the therapeutic concentration but decreased to 4.16 ± 3.53 mcg/ml within seven hours. However, a single sc injection of 30 mg/kg did not achieve the minimum effective leven (Cmax = 3.10 ± 0.14 mcg/m1). THE VETERINARY QUARTERLY, VOL.
12, No. 3, JULY 1990
169
Tissue data
The tissue concentrations of chloramphenicol were evaluated from samples collected in the second experimental group (Fig. 2). The elimination rate constant
was calculated by linear regression for each tissue (Table 2). The mean time required to reach a level of 10 mcg/kg in different tissues was calculated from the kinetic equation. 6
Mumh
5
1
Liver
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
4 K
3
a
K M.
fo,
-de IS
2
Pawn]
0 4h
24h
10 h
336 h
rme
Fig. 2. Tissue residues of chloramphenicol after a single intramuscular administration of chloramphenicol (30 mg/kg). K.C. : Kidney Cortex K.M.: Kidney Medulla I.S.: Injection Site Table 2.
Elimination of chloramphenicol from sheep tissues after a single irvi administration of 30
mg/kg. Tissues
equation
calculated time in hours , to reach 10 mcg/kg
muscle liver kidney
19983.73 e (- 0.214 0
36 - (27-49)* 6 - (1-44)
Inj. site
cortex medulla im
16.21 e (- 0.832 t) 94.20 e (-0.11000 1537.56 e (- "80 248280.00 e (- 0.025 0
21
37
400
- (3-91)
-
(25-60)
- (230-680)
* = confidence region of 95% in sheep population.
The present study shows that chloramphenicol residues remained at the injection site and that 400 hours i.e. 16.66 days should be necessary to obtain the level of 10 mcg/kg at the site, whereas, for example, 6 hours are sufficient to reach this level in the liver. . Plasma creatine phospho-kinase Plasma creatine phospho-kinase levels following subcutaneous and intramuscular administration of chloramphenicol are given in Table 3. 170
THE VETERINARY QUARTERLY, VOL. 12,
No. 3, JULY 1990
Table 3. Plasma serum ccreatine phospho-kinase following the administrations of chloramphenicol (mU/m1).
intramuscular route (n = 8)
subcutaneous route (n = 6)
Time post injection
42.48 ± 18.1 1151.12 ± 556.04 473.16 ± 220.04 256.91 ± 171.79 151.73 ± 74.59 53.04 ± 18.63 26.63 ± 2.57 34.31 ± 36.06
35.85 ± 19.02
0 4
115.21 ± 91.98
45.69 ± 58.47 41.42 ± 39.15 29.79 ± 7.50 31.93 ± 17.33
12
24 48 72 96
18.57 23.92
144
± 1.77 ± 8.44
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
Values are means ± standard deviation.
100
10
1
0
1
24
72
48
Time
96
120
(h1
Fig. 3. Semilogarithmic plot of plasma chloramphenicol concentrations (mcg/ml) vs. time (h) after simulation of intramuscular and subcutaneous chloramphenicol treatment with 6 injections at 12-hour intervals. Therapeutic chloramphenicol level (5 mcg/m1): Mean plasma data after a single administration of 30 mg/kg by
-- -
- intramuscular route: - subcutaneous route:
a AA
Simulation of a treatment with 6 injections of Chloralon at 12-hour intervals.
- Intramuscular simulation - 60 mg/kg/12 - Subcutaneous simulation - 45 mg/kg/I2
h. h: ...........
DISCUSSION
The curve obtained after iv injection was characteristic of a two-compartment model. In sheep, chloramphenicol disposition is described by the same model as in cattle (1, 11). The previous works on sheep (4, 12) have not described the kinetics
of chloramphenicol disappearance from plasma after iv administration. In this study, the following pharmacokinetic parameters were established: plasma halflife 0/2 B = 1.7 hour, volumes of distribution Vd = 0.691 ± 0.019 1/kg, Vc = 0.289
± 0.034 1/kg and clearance CI = 4.66 ± 0.22 ml/min. Amongst the different THE VETERINARY QUARTERLY, VOL. 12, No. 3, JULY 1990
171
pharmacokinetics of chloramphenicol studied in domestic animals, the 0/2 B
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
determined was of the same order as in swine (1.3 h) and goats (2 h) (3). In cattle (11), these values are higher and range from 2.50 to 5.33 hours, probably due to a lower metabolic rate (13). Values for the apparent volume of distribution Vd are only twice that of the central volume Vc; they are close to those found in cattle (Vd = 0.859 ± 0.1241/kg, Vc = 0.351 ± 0.1161/kg) (11). In sheep, chloramphenicol is well distributed.
After im and sc administrations, the pharmacokinetics of chloramphenicol in sheep were described by two different models: a mono-compartment model after im and a two-compartment model after sc. The slopes of the terminal phases were quite different. The rate constant of elimination B after IN4 administration (0.249 ± 0.124 h-I) is close to that when the product is given by the iv route. After sc administration, this parameter is much lower (0.0382 ± 0.0005 h-I). This difference was a typical case of 'flip-flop', i.e., the final slope of the curve for the sc route agreed with the absorption phase. The absorption rate after sc injection is slower than that after im administration. The slow rate observed when the product is injected sc has already been described and is acknowledged for other drugs (8). The fraction of dose absorbed (F), was respectively, 83.01% and 61.19% after In4 and sc treatments. This difference in absorption explains partially why Cma, is much higher after im than after sc injection. When, for two different routes, the rates and extents of absorption are
similar, such routes are admitted to be bioequivalent. In this case, as these parameters are quite different, the two routes of absorption are not bioequivalent. For bacteriostatic antibiotics, the time during which the blood level is in excess or equal to the effective concentration for specific bacteria is very important. Two or three parenteral doses per day, over several days, are often required to achieve the claimed minimum therapeutic blood concentration generally for 75% of the
72 hours of treatment. The simulation of six administrations of 30 mg/kg of chloramphenicol given every 12 hours by each route showed that the therapeutic blood concentration (5 mcg/m1) would be maintained only for 55% and 29.2%
of the treatment time after Im and sc administration, respectively. Adequate therapeutic conditions to obtain the required level for 75% of the treatment period
were obtained with im administration of the tested product Cloralon, by a simulation of 60 mg per kg body weight every 12 hours for 72 hours, while a 45 mg/kg dose administered subcutaneously according to the same regimen was sufficient to be effective under conditions described above (Fig. 3). Our findings are in good agreement with the experiment conducted on ewes infected with a colony of S. aureus (14). After a single im injection of 50 mg/kg of chloramphenicol, the drug concentration determined using a colorimetric method remained relatively constant (8 mcg/m1) from 4.50 to 12.50 hours. It is important to realise that the solubility and absorption of chloramphenicol
depend on both on formulation and on mode of administration, i.e., per os or per iv, im or sc injection. Chloramphenicol is commercially available as a free base (in our product) or as a succinate, palmitate, glycinate or undecylenate ester. It is important to select the appropriate form of the drug for IN4 injection. A dose of 50 mg/kg by IN4 has been proposed for sheep (2). Under our experimental conditions, after a single intramuscular injection of 30 mg/kg of chloramphenicol to sheep, the persistence in edible tissues (muscle, liver, kidney) was different according to the nature of the tissue. Within two days the residues in the following tested tissues, liver, kidney (cortex and medulla) and
muscle (except the injection-site muscle), had fallen below the 10 mcg of chloramphenicol tolerated per kg. However, at the injection site, intramuscular 172
THE VETERINARY QUARTERLY, VOL 12, No. 3, JULY 1990
deposits were higher and about 17 days would be necessary to attain the tolerated value. This shows the weak bioavailability of chloramphenicol when administered intramuscularly (9). The present results on plasma CPK levels shows that the tolerance appeared to
be better when the product was injected by the subcutaneous route. After subcutaneous administration, the CPK serum enzyme values rose slightly to 3.2 times the pretrial levels, whereas after intramuscular injection they increased almost 27-fold. The CPK level fell to the initial level within 96 hours. Subcutaneous tissue cells are poor in CPK while muscle cells are rich in this enzyme. The small
increase in CPK after subcutaneous administration does not exclude local irritation but indicates less damage to the muscles. CONCLUSION
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
The pharmacokinetics of chloramphenicol in sheep after IN4 and sc administrations
were described by two different models: a mono-compartment model after irvi, and a two-compartment model after sc. The slopes of the terminal phases of IN4 and sc curves and the rates and extents of absorption are quire different, implying that the two routes of absorption are not bioequivalent. Adequate therapeutic conditions to obtain a 5 mcg/ml chloramphenicol blood level during 75% of the treatment were obtained for im administrations of the tested product, Cloralon by a simulation of 60 mg per kg body weight 12 hours for 72 hours, while a 45 mg/kg dose administered subcutaneously according to the same regimen was sufficient to maintain an effective level under the same conditions. The study of the chloramphenicol tissue distribution after im administration showed that intramuscular deposites at the injection site were higher than in other tissue and about 17 days would be necessary for the chloramphenicol to fall to the tolerated level (10 mcg/kg). ACKNOWLEDGEMENTS
The authors thank Mrs J. Manceau and Mr B. Delepine for their technical assistance. REFERENCES I. Burrows GE, Barto PB, Martin B, and Tripp ML. Comparative pharmacokinetics of antibiotics 2. 3.
4.
in newborn calves: Chloramphenicol, lincomycin, and tylosin. Am J Vet Res 1983; 44: 1053-7. Davis LL. Chloramphenicol therapy in large animals. J Am Vet Med Assoc 1981; 178: 309-10.
Davis LE, Neff CA, Baggot JD, and Powers TE. Pharmacokinetics of chloramphenicol in domestic animals. Am J Vet Res 1972; 33: 2259-66. De Corte-Bactcn K, Debackere M. Chloramphenicol plasma levels in horses, cattle and sheep after oral and intramuscular route. Zbl Vet Med (A) 1975; 22: 704-12.
5. De Laistre Banting A and Fanneau de la Horie GC. Subcutaneous and intramuscular injection of oxytetracycline in calves: comparison of serum concentration and local tolerance. J Vet Pharmacol Therap 1987; 10: 184-6. 6.
In FAO/WHO thirty-second report. Comments on residues of specific veterinary drugs.
Antimicrobial agents: chloramphcnicol. 1988; 16. 7. Guillot P and Mourot D. Chloramphenicol and oxytetracycline residues in milk and tissues from cows and bullocks treated with an injectable formulation. Food Additives and Contaminants, 1989 (in press). 8. MacDiarmid SC. The absorption of drugs from subcutaneous and intramuscular injection sites. Veterinary Bulletin 1983; 53: 9-23.
9. Nouws JFM and Ziv G. Serum chloramphenicol levels and the intramuscular bioavability of several parenteral formulations of chloramphenicol in ruminants. The Veterinary Quarterly 1979; 10.
1: 47-58. Nouws JFM, Vree TB, Holtkamp J, Baakman M, Driessens F, and Guelen PJM. Pharmacokinetic,
residue and irritation aspects of chloramphenicol sodium succinate and a chloramphenicol base formulation following intramuscular administration to ruminants. The Veterinary Quarterly 1986; 8: 224-32. THE VETERINARY QUARTERLY. VOL. 12, No. 3, JULY 1990
173
11. Sanders P, Guillot P. and Mourot D, Pharmacokinetics ofa long-acting formulation administered by intramuscular and subcutaneous routes in cattle. J Vet Pharmacol Therap 1988; 11: 183-90. 12. Theodorides VJ, Dicuello CJ, Guarini JR, and Pagano JF. Serum concentrations of chloramphenicol after intraruminal and intra-abomasal administration in sheep. Am J Vet Res 1968; 29: 643-5.
13. Van Miert ASJPAM, Bogaert MG, and Debackere M. Comparative Veterinary Pharmacology, Toxicology and Therapy. MTP Press, Lancaster 1986; 489-500. 14. Ziv G, Bogin E, and Sulman FG. Blood and milk in normal and mastitic cows and ewes after intramuscular administration of chloramphenicol and chloramphenicol sodium succinate. Zbl Vet
Downloaded by [Van Pelt and Opie Library] at 02:52 16 October 2014
(A) 1973; 20: 801-11.
174
THE VETERINARY QUARTERLY. VOL 12, No. 3, JULY 1990
