Lack
of Probenecid Effect on Nonrenal Excretion of Ceftriaxone in Anephric Patients Indravadan
R. Audet,
Patricia
H. Patel,
PhD,
PharmD,
Gail
Peter Morrison,
P. Soni, MD,
BS, John and
Gene
J.
Carbone, A. Gibson,
BS, PharniD
Probenecid has been shown to decrease renal and biliary excretion of organic acids. In a randomized crossover study, the effect of coadministered probenecid on nonrenal excretion of ceftriaxone was studied in six functionally anephric patients in whom ceftriaxone is eliminated exclusively by nonrenal or presumably by biliary excretion. Each patient received 0.5 g IV ceftriaxone without and with probenecid (0.5 g at 10 and 2 hours prior to ceftriaxone and 0.5 g ql2h X 3 doses post ceftriaxone). Serial blood samples were collected over 48 hours and plasma analyzed for ceftriaxone by high performance liquid chromatography (HPLC). Pharmacokinetic analysis was based on a model-independent approach. Probenecid did not significantly affect the disposition of ceftriaxone in this study, thus suggesting that nonrenal excretion of ceftriaxone is not inhibited by probenecid.
C
eftriaxone is a broad-spectrum parenteral cephalosporin antibiotic indicated for the treatment of bacterial infections caused by susceptible grampositive and gram-negative bacteria.1 The pharmacokinetics of ceftriaxone have been studied extensively in humans under single and multiple dose conditions in a variety of study populations.23 The key attributes of the drug are: (1) exceptionally long elimination half-life, 5.8 to 8.7 hours2; (2) concentration-dependent plasma protein binding45 which results in dose-dependent pharmacokinetics if it is based on total plasma concentrations; (3) adequate penetration of the drug into cerebrospinal fluid (CSF) and other body tissues1’2’69; and (4) elimination from the body by renal and nonrenal (presumably biliary) excretion in almost equal proportions, thus allowing an alternate route of elimination when either pathway is impaired.2’1#{176} Renal excretion erned predominantly a small extent by
of ceftriaxone in humans by glomerular filtration tubular secretion.4’5 This
is govand to was con-
From the Department of Drug Metabolism (Dr. Patel, Mr. Soni, and Mr. Carbone), Hoffmann-La Roche Inc., Nutley, NewJersey, and the Hospital of the University of Pennsylvania, (Drs. Audet, Morrison, and Gibson) Philadelphia, Pennsylvania. Address for reprints: I. H. Patel, PhD, Department of Drug Metabolism, Hoffmann-La Roche Inc., Nutley, NJ 07110.
J Clin Pharmacol
1990;30:449-453
firmed recently by Stoeckel and coworkers11 who showed that the renal clearance of free ceftriaxone was decreased from 2.09 to 1.67 mL/min/kg upon coadministration of the drug with probenecid, a well known inhibitor of renal tubular secretion of organic acids.12 In that study,11 the nonrenal clearance (presumed to be biliary clearance since ceftriaxone is not metabolized prior to its renal and biliary excretion)248 was also partially reduced, thereby suggesting that a fraction of biliary clearance is through active secretion process. To investigate this further, we examined the effect of probenecid on ceftriaxone pharmacokinetics in functionally anephric patients in whom ceftriaxone is almost exclusively eliminated through nonrenal (presumably biliary) excretion into the feces. This approach allowed us to examine the effect of probenecid solely on the biliary clearance of ceftriaxone without the complication of its effect on renal clearance.
METHODS Patient
Selection
Six stabilized functionally anephric patients (creatinine clearance < 5 mL/min) ranging in age from 24 to 58 years (mean, 45 years) and in body weight from 51.8 to 59.7 kg (mean, 57.0 kg) completed the study.
449
PATEL
These patients modialysis at
were maintained on intermittent henot less than 48 hours apart. The patients demonstrated good general health, except for the renal disease, as determined by baseline history, physical examination, vital signs, and blood chemistries.
Study
Design
The study was approved by the Committee on Studies Involving Human Beings at the Hospital of the University of Pennsylvania and all patients gave written, informed consent prior to their participation in the study. The study was performed using an open label, 2-way randomized, balanced crossover design in which patients received a 0.5 g intravenous (IV) dose of ceftriaxone on two separate occasions; alone and during probenecid treatment (0.5 g oral dose at 10 and 2 hours prior to and at 12, 24, and 36 hours after ceftriaxone dose). Both ceftriaxone dosages were administered intravenously over 30 minutes using a constant rate infusion device and were separated by at least a 10-day washout period. Each ceftriaxone dose was given in the morning of a nondialysis day. All patients stayed at the study site from 12 hours before to 48 hours after each ceftriaxone dose. Blood samples (4 mL) were collected before initiating ceftriaxone infusion and at 0.25, 0.5, 1, 2, 4, 8, 12, 18, 24, 36, and 48 hours after initiation of the ceftriaxone infusion, Additionally, separate 4 mL blood samples were obtained at 0.5, 12, and 24 hours for plasma protein binding measurements. All blood samples were drawn from the arm contralateral to the site of the infusion into heparinized Vacutainer#{174} tubes (Becton Dickinson, Rutherford, NJ). After centrifugation, the plasma was transferred to scintillation vials and promptly frozen in an upright position at -20#{176}C. Analytical
Methods
concentrations of total ceftriaxone were by a previously described high performance liquid chromatography (HPLC) method.13 The interand intra-assay precisions for the method were 2.1% and 2.0%, respectively, over a concentration range of 2.0 to 400.0 g/mL. The sensitivity limit was 2.0 ig/mL using 0.25 mL of plasma. Plasma concentrations of probenecid were determined by slight modifications of a previously reported HPLC method.14 To a 0.1 mL aliquot of plasma. 50 ,l of the reference standard, (Ro 5-2922, 1.25 zg/50 zL acetonitrile) and 150 zL of acetonitrile were added and vortexed for 30 seconds. The samples were centrifuged in a refrigerated centrifuge at Plasma
measured
450
e
J Clin Pharmacol
1990;30:449-453
ET
AL
15#{176}Cfor 10 minutes at 2100 rpm. Supernate was transferred into a low volume insert fitted on a spring of a Waters glass injection vial capped with a self-seal system cap. The HPLC system consisted of a model M6000A reciprocating piston pump (Waters Associates, Milford, MA), a Waters Intelligent Sample Processor (WISPTM) model 71DB and a Waters 440 UV detector using a 254 nm filter, at a sensitivity of 0.02 AUFS. Samples were run on a Whatman Partisil-lO ODS 3 column. The isocratic mobile phase consisted of methanol:water:glacial acetic acid (70:30:1, v/v) delivered at a constant flow rate of 1.5 mL/min. The auto-injector (WISPTM 71DB) was programmed to inject 10 il for HPLC analysis. The interand intra-assay precisions for the probenecid assay were 1.5% and 0.9%, respectively, over a concentration range of 2.4 to 96.0 zg/mL. The sensitivity limit was 2.4 zg/mL using 0.1 mL of plasma.
Pharmacokinetic
Analysis
parameters of ceftriaxone were estimated using a model-independent approach. The terminal elimination rate constant (3) was estimated by linear least-squares regression analysis of the terminal log-linear portion of the plasma concentration-time curve. Three to six plasma concentrations were utilized to estimate 4 and the correlation coefficient ranged from 0.89 to 1.00. The area under the plasma concentration-time curve from time zero to infinity (AUC) was determined by conventional linear trapezoidal summation and extrapolation methods. The systemic clearance (Clj, the volume of distribution in the [ phase (Vd0), the volume of distribution at steady state (Vdj, and the mean residence time (MRT) were estimated using the appropriate relationships published elsewhere.15 Pharmacokinetic
Protein
Binding
Plasma samples were subjected perature using protein binding of ceftriaxone one concentration one
concentration
obtained at 0.5, 12, and 24 hours to ultracentrifugation at room temAmicon filtration kits to determine of ceftriaxone.16 The free fraction (fr) was determined by dividing ceftriaxin the ultrafiltrate with ceftriaxin plasma prior to filtration.
RESULTS Probenecid had no effect on the average plasma concentration-time profiles of ceftriaxone (Figure) and the associated pharmacokinetic parameters of ceftriaxone (Table I) such as Cmax (70.5 vs 65.8 g/mL), AUC (1420 vs 1233 zg.h/mL), tl/z (21.6 vs 19.9 h), MRT (32.1 vs 30.2 h), Cl5 (455 vs 481 mL/h)
CEFTBIAXONE
KINETICS
IN ANEPHBICS
TABLE
I
Pharmacokinetic Parameters of Total Ceftriaxone After a 0.5 g Intravenous Dose of Ceftriaxone Alone and with Probenecid Ceftriaxone Alone
Ceftriaxone Plus Probenecid
Paired f-test Analysis
70.5 ± 11.3 55.5_90.1* 1420 ± 949
65.8 ± 13.0 50.9-82.4 1233 ± 588
NS
689-3231 0.032 ± 0.012 0.015-0.047
658-2021 0.035 ± 0.015 0.020-0.058
Parameter Cma,
(sg/mL)
AUC
(pg.
h/mL)
(3 (h’)
19.9t 12.0-34.8 30.2 ± 12.4 16.1-44.8 481 ± 197 247-760 14.8 ± 7.0 9.3-28.5 13.1 ± 5.2 9.6-23.6
21.6t
(h)
t112
14.8-45.6 MRT (h)
± 16.4 18.9-63.8 455 ± 203 155-725 14.7 ± 7.1 10.0-28.2 12.5 ± 4.2 9.5-20.4
32.1
CL (mL/h) Vd Figure. Mean plasma concentration-time profiles of total ceftriaxone following a single 30-minute intravenous infusion of a 0.5 ceftriaxone dose alone (.1 and with oral probenecid (U).
(L)
Vd55 (L) g
Vd5. (12.5 vs 13.1 L). Also, the free fraction II) of ceftriaxone after both treatments was similar at 0.5 hours (0.17 vs 0.21), 12 hours (0.17 vs 0.19) and at 24 hours (0.22 vs 0.19). Statistical analysis using the paired t test indicated no significant differences (NS), at 5% level of significance, between the two treatments in any of the pharmacokinetic parameters observed. These findings indicated that the pharmacokinetics of ceftriaxone in functionally anephric patients was not significantly influenced by probenecid. There was also no effect of probenecid on the protein binding of ceftriaxone. Plasma samples collected for the first 12 hours after the ceftriaxone dose in the combination treatment were assayed for probenecid by HPLC (Table III). These samples contained concentrations of probenecid which are known to inhibit active secretion of drugs. Since the probenecid dose was given 2 hours prior to the ceftriaxone dose, it was not possible to evaluate the pharmacokinetics of probenecid comprehensively in the patients. However, it was possible to estimate the elimination half-life of probenecid which ranged from 8.2 to 17.5 hours (harmonic mean, 9.7 h) in the six patients.
NS NS
NS NS
NS NS NS
Mean ± SD and range. t Harmonic mean.
and
(Table
TABLE
The observed kinetic absence of probenecid
AGENTS
profile in the
of ceftriaxone in the renal failure patients is
II
Free Fraction of Ceftriaxone in Plasma at 0.5, 12 and 24 hours After a 0.5 g Intravenous Dose of Ceftriaxone Alone and with Probenecid Ceftriaxone Alone
Time (h)
0.5 12 24
Average
DISCUSSION
ANTI-INFECTIVE
consistent with that reported previously by other investigators.1722 According to these investigators, the elimination half-life ranged from 12.7 to 18.2 hours, the systemic plasma clearance from 538 to 798 mL/h and the volume of distribution from 11.4 to 16.8 L.
Mean
±
Ceftriaxone Plus Probenecid
0.17 ± 0.04 0.11_0.23* 0.17 ± 0.05 0.11-0.24 0.22 ± 0.11 0. 10-0.36
0.21
0.19 ± 0.06 0.12-0.26
0.20 ± 0.08 0.12-0.31
± 0.12
0.11-0.38 0.19 ± 0.09 0. 10-0.34 0.19 ± 0.05 0. 10-0.26
Paired f-test Analysis NS
NS NS
NS
SD and range.
451
PATEL
TABLE Probenecid Elimination
Plasma Half-Life
Time (h)
Mean
2.25 2.5 3 4 6 10
51.5 53.7 51.3 54.4 43.5 33.1
14
24.6 0.071
(3(h’) t1,2
(h)
III
Concentrations (ig/mL) After a 0.5 g Probenecid ±SD
17.8 19.7 14.3 6.5 8.1 7.0 4.9
0.016
Range
23.8-71.3 39.1-84.0 26.5-64.9 44.8-63.2 31.2-55.1 21.8-40.4 17.5-30.3
0.040-0.084 8.2-17.5
97*
Harmonic
and Dose
mean.
The influence of probenecid on the pharmacokinetic profile of ceftriaxone in healthy subjects was investigated in two previous studies.1123 In the first study,23 probenecid induced no changes in the disposition of total (unbound + bound drug in plasma) ceftriaxone. Inadequate dosage regimen of probenecid (0.5 g probenecid 2 hours and 10 minutes prior to a 0.5 g ceftriaxone intravenous dose) was believed to be the cause for the lack of inhibitory effect of probenecid in that study. In a more recent comprehensive study,1t which maintained probenecid levels over a longer interval (0.5 g q6h X 10 doses), probenecid induced significant changes in several disposition parameters of ceftriaxone. Specifically, probenecid reduced renal and nonrenal clearance of unbound ceftriaxone, caused a paradoxical increase in plasma clearance of total ceftriaxone, shortened the elimination half-life and increased the steady state volume of distribution secondary to an increase in the average free fraction in plasma. The reduction in nonrenal (or biliary) clearance was modest and suggested that a small fraction of biliary clearance is via active secretion of the drug into bile. In our study, even though a probenecid regimen was maintained for 48 hours, biliary clearance was unchanged suggesting that either the drug is minimally secreted into the bile via active transport or that the active transport process was impaired considerably in our patients and therefore could not be influenced by probenecid. Diminished nonrenal clearance in renal failure patients has been reported for other drugs2425 which may be a secondary effect of the disease state of the active transport and/or hepatic metabolism involved in the nonrenal elimination.26
452
#{149} J Clin Pharmacol
1990;30:449-453
ET
AL
A less frequent dosage regimen of probenecid (ql2h vs q6h) was preferred in the present study because of anticipatory reduced elimination of probenecid in the renal failure patients. The mean elimination half-life of probenecid in the renal failure patients (9.7 h) was almost two-fold longer than that reported in healthy subjects (4-5 h)2728 and justify the selected dosage frequency of probenecid in the study. The lack of displacement effect of probenecid on the protein binding of ceftriaxone is surprising since it was quite pronounced (the average free fraction of ceftriaxone in plasma increased by 50 to 70%) in the study of Stoeckel and coworkers.11 Since ceftriaxone and probenecid bind at different sites on the albumin molecule, the observed displacement effect was explained on the basis of negative cooperativity.11 The lack of displacement effect at adequate concentrations of probenecid in the present study suggests an absence of the negative cooperativity effect in the plasma of renal failure patients. This may have occurred in our patients because of a build-up of endogenous inhibitors in plasma of such patients which through some complex interactions with probenecid and ceftriaxone for binding sites may have obliterated the displacement effect seen in the healthy subjects. As such, the results of the study are of limited clinical significance considering that ceftriaxone is generally given at higher doses (1 to 2 g) and mostly to patients with normal renal and biliary functions. However, the results of this study and previous investigations11’23 have shown little, if any, pharmacokinetic interaction between ceftriaxone and probenecid. Consequently, precautionary measures would not be necessary in the unlikely event that ceftriaxone and probenecid are coadministered.
REFERENCES 1. Richards
DM,
Ceftriaxone-A cal properties
Heel
RC, Brogden
RN, Speight
review of its antibacterial and therapeutic use. Drugs
2. Patel IH, Kaplan SA: Pharmacokinetic man. Am J Med 1984;77(4C):17-25. 3. Hayton WL. pharmacokinetics.
Stoeckel Clin
K: Age associated Pharmacokinet
TM,
Avery
profile
of ceftriaxone
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ceftriaxone
kinetics.
Clin
in
in ceftriaxone
4. Stoeckel K, McNamara PJ, Brandt R, Plozza-Nottebrock Ziegler WM: Effects of concentration-dependent plasma binding on 1981:29:650-657.
GM:
activity, pharmacologi1984:27:469-527.
Pharmacol
M,
protein Ther
McNamara PJ, Stoeckel K. Ziegler WH: Pharmacokinetics of ceftriaxone following intravenous administration of a 3 g dose. Eur J Clin Pharmacol 1982:22:71-75. 5.
6. Just
MM, Frank trations of ceftriaxone 1984:30:81-83.
U, Simon A, in serum
Kaiser and
D, Daschner lung tissue.
FD: ConcenChemotherapy
CEFTBIAXONE
7. Dascher FD, Peterson EE, Brandle j, Hillemanns trations of Ceftriaxone in serum and gynecological motherapy 1983:29:153-155. 8.
Hayton
WL,
Schandalik
R, Stoeckel
pharmacokinetics of ceftriaxone Pharmacol 1986:30:445-451. 9.
Billstein
SA:
Ceftriaxone
1988:34(Suppl
1):53-58.
10. Stoeckel tients with
K. Kemp renal and
physiological
HG: Concentissues. Che-
K: Biliary
after
KINETICS
excretion
cholecystectomy.
Kinetic
Chemotherapy
and JR: Pharmacokinetics liver insufficiency protein
of ceftriaxone and correlations
binding
model.
Am
in pawith a J Med
1984;77(4C):26-32. 11. Stoeckel K, Trueb V. Duback UC, McNamara PH: Effect probenecid on the elimination and protein binding of ceftriaxone. Eur J Clin Pharmacol 1988:34:151-156. 12. Cunningham RF, Israili ZM, Dayton PC: Clinical pharmacokinetics of probenecid. Clin Pharmacokinet 1981:6:135-151. 5, Parsonnet M, Hackman MR. Brooks SA: Pharmacokinetics of ceftriaxone Agents Chemother 1981:20:634-641.
14. Smith evaluation
DE, Gee WL, Brater DC, Lin ET, Benet of furosemide-probenecid interaction
Pharm
1980:69:571-575.
Sci
macokinetics 1986:30:303-307.
and
Eur J Clin
of tissues.
LZ:
of
MA, in
Preliminary
I
in humans.
15. Gibaldi M, Perrier D: Noncompartmental analysis based on statistical moment theory, in Gibaldi M. Perrier D (eds): Pharmacokinetics, 2nd ed. New York, Marcel Dekker, 1982; 409-417. SF,
McCormick cefoperazone
EM, Echols RM: and ceftizoxime.
17. Stoeckel K, McNamara PJ, Hoppe-Seyler Keller E: Single-dose ceftriaxone in functionally tients. Clin Phormacol Tlier 1983;33:633-641. 18.
Kowalsky
ANTI-INFECTIVE
SF, Echols
AGENTS
ysis.
RM,
Parker
MA:
C, Blumberg anephric
Pharmacokinetics
A, paof
Ti T-Y,
during
Fortin
patients
renal
L, Kreeft
dialysis.
JH, East
of intravenous
with
Antimicrob
renal
Chemother
Clin
Pharm
K: Ceftriaxone Eur
DS, Ogilvie ceftriaxone
failure
Agents
insufficiency.
H, Stoeckel
peritoneal
disposition
21. Cohen cefiriaxone hemodialysis.
I Clin
phar-
Pharmacal
RI, Somerville in normal
PJ:
subjects
on hemodialysis or peritoneal 1984:25:83-87.
dial-
D, Appel GB, Scully B, Neu HC: Pharmacokinetics in patients with renal failure and in those undergoing Antimicrob Agents Chemother 1983;24:529-532.
22. Patel lH, Sugihara Berman SJ: Ceftriaxone ious degrees of renal 1984:25:438-442.
of
JG, Weinfeld RE, Wong EGC, Siemsen AW, pharmacokinetics in patients with varimpairment. Antimicrob Agents Chemother
23. Stoeckel K: Pharmacokinetics of Rocephin. a highly active new cephalosporin with an exceptionally long biological half-life. Chemotherapy 1981;27(Suppl 1):42-46. 24. Gibson TP, Atkinson AJ Jr. Matusik E, Nelson Kinetics of procainamide and n-acetylprocainamide ure. Kidney mt 1977:12:422-429.
25.
16. Hamilton RA, Kowalsky Protein binding of ceftriaxone, Clin Pharm 1987:6:567-569.
ANEPHRICS
ceftriaxone in subjects with 1985 :4: 177-181. 19. Koup JR, Keller E, Neumann
20. penetration
nonlinear
13. Patel lH, Chen Konikoff J, Kaplan humans. Anitmicrob
IN
Gibson
TP, Grannemann
din kinetics 1982:31:602-608.
on
26.
renal
Balant LP. Dayer on the hepatic Bes 1983:3:459-474. ciency
CR, Kallal impairment.
P. Fabre clearance
J: Consequences
27. Selen A, Amidon CL, Welling PC: benecid following oral doses to human
in
JE, Sennello Clin
of some
LD,
drugs.
Briggs renal
WA: fail-
LT: CefsuloTher
Pharmacol
of renal tnt J Clin
Pharmacokinetics volunteers.
insuffiPharm
of proJ Pharm Sci
1982:71:1238-1242.
28. Emanuelsson elimination and macol
B-M, protein
Beermann binding
B, Paalzow of probenecid.
LK: Non-linear Eur J Clin Phar-
1987:32:395-401.
453
of Probenecid Effect on Nonrenal Excretion of Ceftriaxone in Anephric Patients Indravadan
R. Audet,
Patricia
H. Patel,
PhD,
PharmD,
Gail
Peter Morrison,
P. Soni, MD,
BS, John and
Gene
J.
Carbone, A. Gibson,
BS, PharniD
Probenecid has been shown to decrease renal and biliary excretion of organic acids. In a randomized crossover study, the effect of coadministered probenecid on nonrenal excretion of ceftriaxone was studied in six functionally anephric patients in whom ceftriaxone is eliminated exclusively by nonrenal or presumably by biliary excretion. Each patient received 0.5 g IV ceftriaxone without and with probenecid (0.5 g at 10 and 2 hours prior to ceftriaxone and 0.5 g ql2h X 3 doses post ceftriaxone). Serial blood samples were collected over 48 hours and plasma analyzed for ceftriaxone by high performance liquid chromatography (HPLC). Pharmacokinetic analysis was based on a model-independent approach. Probenecid did not significantly affect the disposition of ceftriaxone in this study, thus suggesting that nonrenal excretion of ceftriaxone is not inhibited by probenecid.
C
eftriaxone is a broad-spectrum parenteral cephalosporin antibiotic indicated for the treatment of bacterial infections caused by susceptible grampositive and gram-negative bacteria.1 The pharmacokinetics of ceftriaxone have been studied extensively in humans under single and multiple dose conditions in a variety of study populations.23 The key attributes of the drug are: (1) exceptionally long elimination half-life, 5.8 to 8.7 hours2; (2) concentration-dependent plasma protein binding45 which results in dose-dependent pharmacokinetics if it is based on total plasma concentrations; (3) adequate penetration of the drug into cerebrospinal fluid (CSF) and other body tissues1’2’69; and (4) elimination from the body by renal and nonrenal (presumably biliary) excretion in almost equal proportions, thus allowing an alternate route of elimination when either pathway is impaired.2’1#{176} Renal excretion erned predominantly a small extent by
of ceftriaxone in humans by glomerular filtration tubular secretion.4’5 This
is govand to was con-
From the Department of Drug Metabolism (Dr. Patel, Mr. Soni, and Mr. Carbone), Hoffmann-La Roche Inc., Nutley, NewJersey, and the Hospital of the University of Pennsylvania, (Drs. Audet, Morrison, and Gibson) Philadelphia, Pennsylvania. Address for reprints: I. H. Patel, PhD, Department of Drug Metabolism, Hoffmann-La Roche Inc., Nutley, NJ 07110.
J Clin Pharmacol
1990;30:449-453
firmed recently by Stoeckel and coworkers11 who showed that the renal clearance of free ceftriaxone was decreased from 2.09 to 1.67 mL/min/kg upon coadministration of the drug with probenecid, a well known inhibitor of renal tubular secretion of organic acids.12 In that study,11 the nonrenal clearance (presumed to be biliary clearance since ceftriaxone is not metabolized prior to its renal and biliary excretion)248 was also partially reduced, thereby suggesting that a fraction of biliary clearance is through active secretion process. To investigate this further, we examined the effect of probenecid on ceftriaxone pharmacokinetics in functionally anephric patients in whom ceftriaxone is almost exclusively eliminated through nonrenal (presumably biliary) excretion into the feces. This approach allowed us to examine the effect of probenecid solely on the biliary clearance of ceftriaxone without the complication of its effect on renal clearance.
METHODS Patient
Selection
Six stabilized functionally anephric patients (creatinine clearance < 5 mL/min) ranging in age from 24 to 58 years (mean, 45 years) and in body weight from 51.8 to 59.7 kg (mean, 57.0 kg) completed the study.
449
PATEL
These patients modialysis at
were maintained on intermittent henot less than 48 hours apart. The patients demonstrated good general health, except for the renal disease, as determined by baseline history, physical examination, vital signs, and blood chemistries.
Study
Design
The study was approved by the Committee on Studies Involving Human Beings at the Hospital of the University of Pennsylvania and all patients gave written, informed consent prior to their participation in the study. The study was performed using an open label, 2-way randomized, balanced crossover design in which patients received a 0.5 g intravenous (IV) dose of ceftriaxone on two separate occasions; alone and during probenecid treatment (0.5 g oral dose at 10 and 2 hours prior to and at 12, 24, and 36 hours after ceftriaxone dose). Both ceftriaxone dosages were administered intravenously over 30 minutes using a constant rate infusion device and were separated by at least a 10-day washout period. Each ceftriaxone dose was given in the morning of a nondialysis day. All patients stayed at the study site from 12 hours before to 48 hours after each ceftriaxone dose. Blood samples (4 mL) were collected before initiating ceftriaxone infusion and at 0.25, 0.5, 1, 2, 4, 8, 12, 18, 24, 36, and 48 hours after initiation of the ceftriaxone infusion, Additionally, separate 4 mL blood samples were obtained at 0.5, 12, and 24 hours for plasma protein binding measurements. All blood samples were drawn from the arm contralateral to the site of the infusion into heparinized Vacutainer#{174} tubes (Becton Dickinson, Rutherford, NJ). After centrifugation, the plasma was transferred to scintillation vials and promptly frozen in an upright position at -20#{176}C. Analytical
Methods
concentrations of total ceftriaxone were by a previously described high performance liquid chromatography (HPLC) method.13 The interand intra-assay precisions for the method were 2.1% and 2.0%, respectively, over a concentration range of 2.0 to 400.0 g/mL. The sensitivity limit was 2.0 ig/mL using 0.25 mL of plasma. Plasma concentrations of probenecid were determined by slight modifications of a previously reported HPLC method.14 To a 0.1 mL aliquot of plasma. 50 ,l of the reference standard, (Ro 5-2922, 1.25 zg/50 zL acetonitrile) and 150 zL of acetonitrile were added and vortexed for 30 seconds. The samples were centrifuged in a refrigerated centrifuge at Plasma
measured
450
e
J Clin Pharmacol
1990;30:449-453
ET
AL
15#{176}Cfor 10 minutes at 2100 rpm. Supernate was transferred into a low volume insert fitted on a spring of a Waters glass injection vial capped with a self-seal system cap. The HPLC system consisted of a model M6000A reciprocating piston pump (Waters Associates, Milford, MA), a Waters Intelligent Sample Processor (WISPTM) model 71DB and a Waters 440 UV detector using a 254 nm filter, at a sensitivity of 0.02 AUFS. Samples were run on a Whatman Partisil-lO ODS 3 column. The isocratic mobile phase consisted of methanol:water:glacial acetic acid (70:30:1, v/v) delivered at a constant flow rate of 1.5 mL/min. The auto-injector (WISPTM 71DB) was programmed to inject 10 il for HPLC analysis. The interand intra-assay precisions for the probenecid assay were 1.5% and 0.9%, respectively, over a concentration range of 2.4 to 96.0 zg/mL. The sensitivity limit was 2.4 zg/mL using 0.1 mL of plasma.
Pharmacokinetic
Analysis
parameters of ceftriaxone were estimated using a model-independent approach. The terminal elimination rate constant (3) was estimated by linear least-squares regression analysis of the terminal log-linear portion of the plasma concentration-time curve. Three to six plasma concentrations were utilized to estimate 4 and the correlation coefficient ranged from 0.89 to 1.00. The area under the plasma concentration-time curve from time zero to infinity (AUC) was determined by conventional linear trapezoidal summation and extrapolation methods. The systemic clearance (Clj, the volume of distribution in the [ phase (Vd0), the volume of distribution at steady state (Vdj, and the mean residence time (MRT) were estimated using the appropriate relationships published elsewhere.15 Pharmacokinetic
Protein
Binding
Plasma samples were subjected perature using protein binding of ceftriaxone one concentration one
concentration
obtained at 0.5, 12, and 24 hours to ultracentrifugation at room temAmicon filtration kits to determine of ceftriaxone.16 The free fraction (fr) was determined by dividing ceftriaxin the ultrafiltrate with ceftriaxin plasma prior to filtration.
RESULTS Probenecid had no effect on the average plasma concentration-time profiles of ceftriaxone (Figure) and the associated pharmacokinetic parameters of ceftriaxone (Table I) such as Cmax (70.5 vs 65.8 g/mL), AUC (1420 vs 1233 zg.h/mL), tl/z (21.6 vs 19.9 h), MRT (32.1 vs 30.2 h), Cl5 (455 vs 481 mL/h)
CEFTBIAXONE
KINETICS
IN ANEPHBICS
TABLE
I
Pharmacokinetic Parameters of Total Ceftriaxone After a 0.5 g Intravenous Dose of Ceftriaxone Alone and with Probenecid Ceftriaxone Alone
Ceftriaxone Plus Probenecid
Paired f-test Analysis
70.5 ± 11.3 55.5_90.1* 1420 ± 949
65.8 ± 13.0 50.9-82.4 1233 ± 588
NS
689-3231 0.032 ± 0.012 0.015-0.047
658-2021 0.035 ± 0.015 0.020-0.058
Parameter Cma,
(sg/mL)
AUC
(pg.
h/mL)
(3 (h’)
19.9t 12.0-34.8 30.2 ± 12.4 16.1-44.8 481 ± 197 247-760 14.8 ± 7.0 9.3-28.5 13.1 ± 5.2 9.6-23.6
21.6t
(h)
t112
14.8-45.6 MRT (h)
± 16.4 18.9-63.8 455 ± 203 155-725 14.7 ± 7.1 10.0-28.2 12.5 ± 4.2 9.5-20.4
32.1
CL (mL/h) Vd Figure. Mean plasma concentration-time profiles of total ceftriaxone following a single 30-minute intravenous infusion of a 0.5 ceftriaxone dose alone (.1 and with oral probenecid (U).
(L)
Vd55 (L) g
Vd5. (12.5 vs 13.1 L). Also, the free fraction II) of ceftriaxone after both treatments was similar at 0.5 hours (0.17 vs 0.21), 12 hours (0.17 vs 0.19) and at 24 hours (0.22 vs 0.19). Statistical analysis using the paired t test indicated no significant differences (NS), at 5% level of significance, between the two treatments in any of the pharmacokinetic parameters observed. These findings indicated that the pharmacokinetics of ceftriaxone in functionally anephric patients was not significantly influenced by probenecid. There was also no effect of probenecid on the protein binding of ceftriaxone. Plasma samples collected for the first 12 hours after the ceftriaxone dose in the combination treatment were assayed for probenecid by HPLC (Table III). These samples contained concentrations of probenecid which are known to inhibit active secretion of drugs. Since the probenecid dose was given 2 hours prior to the ceftriaxone dose, it was not possible to evaluate the pharmacokinetics of probenecid comprehensively in the patients. However, it was possible to estimate the elimination half-life of probenecid which ranged from 8.2 to 17.5 hours (harmonic mean, 9.7 h) in the six patients.
NS NS
NS NS
NS NS NS
Mean ± SD and range. t Harmonic mean.
and
(Table
TABLE
The observed kinetic absence of probenecid
AGENTS
profile in the
of ceftriaxone in the renal failure patients is
II
Free Fraction of Ceftriaxone in Plasma at 0.5, 12 and 24 hours After a 0.5 g Intravenous Dose of Ceftriaxone Alone and with Probenecid Ceftriaxone Alone
Time (h)
0.5 12 24
Average
DISCUSSION
ANTI-INFECTIVE
consistent with that reported previously by other investigators.1722 According to these investigators, the elimination half-life ranged from 12.7 to 18.2 hours, the systemic plasma clearance from 538 to 798 mL/h and the volume of distribution from 11.4 to 16.8 L.
Mean
±
Ceftriaxone Plus Probenecid
0.17 ± 0.04 0.11_0.23* 0.17 ± 0.05 0.11-0.24 0.22 ± 0.11 0. 10-0.36
0.21
0.19 ± 0.06 0.12-0.26
0.20 ± 0.08 0.12-0.31
± 0.12
0.11-0.38 0.19 ± 0.09 0. 10-0.34 0.19 ± 0.05 0. 10-0.26
Paired f-test Analysis NS
NS NS
NS
SD and range.
451
PATEL
TABLE Probenecid Elimination
Plasma Half-Life
Time (h)
Mean
2.25 2.5 3 4 6 10
51.5 53.7 51.3 54.4 43.5 33.1
14
24.6 0.071
(3(h’) t1,2
(h)
III
Concentrations (ig/mL) After a 0.5 g Probenecid ±SD
17.8 19.7 14.3 6.5 8.1 7.0 4.9
0.016
Range
23.8-71.3 39.1-84.0 26.5-64.9 44.8-63.2 31.2-55.1 21.8-40.4 17.5-30.3
0.040-0.084 8.2-17.5
97*
Harmonic
and Dose
mean.
The influence of probenecid on the pharmacokinetic profile of ceftriaxone in healthy subjects was investigated in two previous studies.1123 In the first study,23 probenecid induced no changes in the disposition of total (unbound + bound drug in plasma) ceftriaxone. Inadequate dosage regimen of probenecid (0.5 g probenecid 2 hours and 10 minutes prior to a 0.5 g ceftriaxone intravenous dose) was believed to be the cause for the lack of inhibitory effect of probenecid in that study. In a more recent comprehensive study,1t which maintained probenecid levels over a longer interval (0.5 g q6h X 10 doses), probenecid induced significant changes in several disposition parameters of ceftriaxone. Specifically, probenecid reduced renal and nonrenal clearance of unbound ceftriaxone, caused a paradoxical increase in plasma clearance of total ceftriaxone, shortened the elimination half-life and increased the steady state volume of distribution secondary to an increase in the average free fraction in plasma. The reduction in nonrenal (or biliary) clearance was modest and suggested that a small fraction of biliary clearance is via active secretion of the drug into bile. In our study, even though a probenecid regimen was maintained for 48 hours, biliary clearance was unchanged suggesting that either the drug is minimally secreted into the bile via active transport or that the active transport process was impaired considerably in our patients and therefore could not be influenced by probenecid. Diminished nonrenal clearance in renal failure patients has been reported for other drugs2425 which may be a secondary effect of the disease state of the active transport and/or hepatic metabolism involved in the nonrenal elimination.26
452
#{149} J Clin Pharmacol
1990;30:449-453
ET
AL
A less frequent dosage regimen of probenecid (ql2h vs q6h) was preferred in the present study because of anticipatory reduced elimination of probenecid in the renal failure patients. The mean elimination half-life of probenecid in the renal failure patients (9.7 h) was almost two-fold longer than that reported in healthy subjects (4-5 h)2728 and justify the selected dosage frequency of probenecid in the study. The lack of displacement effect of probenecid on the protein binding of ceftriaxone is surprising since it was quite pronounced (the average free fraction of ceftriaxone in plasma increased by 50 to 70%) in the study of Stoeckel and coworkers.11 Since ceftriaxone and probenecid bind at different sites on the albumin molecule, the observed displacement effect was explained on the basis of negative cooperativity.11 The lack of displacement effect at adequate concentrations of probenecid in the present study suggests an absence of the negative cooperativity effect in the plasma of renal failure patients. This may have occurred in our patients because of a build-up of endogenous inhibitors in plasma of such patients which through some complex interactions with probenecid and ceftriaxone for binding sites may have obliterated the displacement effect seen in the healthy subjects. As such, the results of the study are of limited clinical significance considering that ceftriaxone is generally given at higher doses (1 to 2 g) and mostly to patients with normal renal and biliary functions. However, the results of this study and previous investigations11’23 have shown little, if any, pharmacokinetic interaction between ceftriaxone and probenecid. Consequently, precautionary measures would not be necessary in the unlikely event that ceftriaxone and probenecid are coadministered.
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