ANTIMICROBiAL AGENTS
AND
CHEMOTHERAPY, June 1992, p. 1296-1301
Vol. 36, No. 6
0066-4804/92/061296-06$02.00/0
Multiple-Dose Pharmacokinetics and Safety of Rufloxacin in Normal Volunteers JAMES C. KISICKI,1 RHONDA S. GRIESS,1 CHRISTOPHER L. 0OT,' GUY M. COHEN,2 ROBERT J. McCORMACK,2 WILLIAM M. TROETEL,2 AND BRUNO P. IMBIMBO3* Harris Laboratories, Lincoln, Nebraska 685011; Oxford Research Intemnational, Clifton, New Jersey 07013-42212; and Mediolanum Farnaceutici, Milan, Italy3 Received 16 October 1991/Accepted 6 April 1992
The pharmacokinetics and safety of rufloxacin were evaluated in a double-blind, placebo-controlled study. Two groups of 16 healthy volunteers were given a single oral loading dose of 400 or 600 mg of rufloxacin on day 1 of the study. A single daily maintenance dose of 200 or 300 mg was then administered for a further 9 days; in addition, four subjects in each group received placebos. Rufloxacin levels in plasma and urine were determined by high-performance liquid chromatography. Following the initial dose, the mean (± standard 0.12 ,g/ml in the 400-mg group error of the mean) peak concentrations of rufloxacin in plasma were 3.35 and 4.54 + 0.19 pLglml in the 600-mg group. They were generaly reached 2 to 3 h after dosing. At the end of treatment, maximum levels in plasma rose to 4.51 ± 0.15 and 7.20 ± 0.25 pLg/ml in the 400-mg and 600-mg groups, with a mean extent of accumulation (fold) of 3.1 ± 0.1 and 3.3 ± 0.1. For the 400-mg and 600-mg groups, the elimination half-lives were 40.0 ± 1.5 and 44.0 ± 1.3 h, mean residence times were 57.8 ± 2.2 and 63.7 ± 1.8 h, apparent volumes of distribution were 132 ± 4 and 139 ± 5 liters, and apparent total body clearances were 39 ± 1 and 44 ± 4 ml/min, assuming complete bioavailability. Of the total dose administered, the percentages excreted in urine were 49.6 ± 1.3 and 51.1 ± 2.1%, with renal clearances of 21 ± 1 and 22 ± 2 ml/min, for the 400-mg and 600-mg groups. On the whole, the treatments were well tolerated, but some minor adverse events (mainly headache, insomnia, or abdominal discomfort) were reported for 7 subjects on the low-dose regimen, for 12 subjects on the high-dose regimen, and for 3 subjects taking placebos. No abnormalities were detected in the laboratory examinations or in ocular function tests. This study shows that a 200-mg daily oral dose of rufloxacin preceded by a loading dose of 400 mg are well tolerated and produce steady-state concentrations in plasma above the MIC for most susceptible pathogens. 9 days (the 600-mg group). Four subjects in each group received placebos in a double-blind fashion. Each dose was taken with about 50 ml of water at about 7:00 a.m. after an overnight fast. Fasting was continued for a further 2 h after the administration of the drug. At 9:00 a.m., a standardized breakfast of 700 kcal (ca. 3,000 kJ) was consumed. Breakfast generally consisted in two eggs with two bacon strips or two sausage links, two slices of toast with margarine and jelly or syrup, 6 oz (ca. 180 ml) of juice, and 8 oz (ca. 240 ml) of milk or coffee. A standardized lunch (1,000 kcal [ca. 4,000 kJJ) was given at 12:00 noon. Water was given ab libitum. All volunteers were outpatients. During sample collection periods and fasting periods, volunteers recovered in the Harris Laboratories Clinical Research Unit, Lincoln, Nebr. Subjects. Forty healthy male subjects completed this study: 32 were Caucasian, 3 were Black, 3 were Asian, 1 was Hispanic, and 1 was Indian. Demographic characteristics of the two treatment groups did not differ significantly (Table 1). All subjects were judged to be in good health as determined by physical examination, complete ophthalmological examination, electrocardiogram, full blood count, coagulation tests, serum chemistry profiles, and complete urinalysis. None of the subjects had a history of serious systemic illness, drug or alcohol abuse, or hypersensitivity to any food or drug. All subjects gave written informed consent before entering the study. The protocol of the study was approved by the Harris Laboratories Institutional Review Board. Safety evaluation. An extensive series of tests was carried out on every subject during each dosing period. Physical examinations were performed during preselection and at the
Rufloxacin is a new quinolone antibacterial agent (1) (Fig. 1). This drug has been shown to possess marked in vitro and in vivo activity against gram-negative and gram-positive bacteria (9, 13). Single-dose pharmacokinetic studies in normal volunteers showed that an oral dose of 400 mg of rufloxacin is eliminated slowly, with a plasma half-life of 30 to 40 h (7, 15). The study described here was designed to evaluate the pharmacokinetics and safety of multiple oral doses of rufloxacin. The results of this study should lead to the formulation of appropriate dosage regimens for the treatment of infectious diseases caused by rufloxacin-susceptible organisms. (Part of this work was presented at the 17th International Congress of Chemotherapy, Berlin, 23 to 28 June 1991 [abstract 379].)
MATERIALS AND METHODS Study design. Forty healthy male volunteers were randomly divided into two groups of 20 subjects. Rufloxacin (Mediolanum Farmaceutici, Milan, Italy) capsules were prepared by the Division of Pharmaceutical Service, College of Pharmacy, The University of Iowa. In the first group, 16 subjects were given a single loading dose of 400 mg (two capsules of 200 mg) on day 1 and single doses of 200 mg (one capsule) on the subsequent 9 days (the 400-mg group). In the second group, 16 subjects were given a single loading dose of 600 mg (four capsules of 150 mg) on the first day and single doses of 300 mg (two capsules of 150 mg) on the subsequent *
Corresponding author. 1296
VOL. 36, 1992
PHARMACOKINETICS AND SAFETY OF RUFLOXACIN
FIG. 1. Structural formula of rufloxacin.
end of treatment. Vital signs were monitored every day. Electrocardiograms were performed during preselection and 24 h after the last dose. Complete ophthalmological examinations, including visual acuity, slit lamp examination, funduscopic examination, Farnsworth hue color test, and electroretinogram, were carried out during preselection and 24 h after the last dose. Hematological tests (hemoglobin, hematocrit, erythrocyte count, leukocyte count, neutrophils, lymphocytes, eosinophils, basophils, monocytes, and platelets), coagulation tests (prothrombin time, activated partial thromboplastin time, and bleeding time), and chemistry profiles of serum (fasting blood glucose, urea nitrogen, sodium, potassium, chloride, carbon dioxide, magnesium, serum creatinine, uric acid, calcium, inorganic phosphorus, cholesterol, high-density lipoproteins, tryglycerides, total protein, albumin, globulin, total bilirubin, direct bilirubin, serum aspartate aminotransferase, serum alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, creatinine phosphokinase, and lactate dehydrogenase) were performed during the preselection phase and repeated each morning before the compound was administered on days 1, 2, 5, and 8 and 24 h after the last dose. Creatinine clearance rates were determined at preselection and after the final dose. Urinalysis, with microscopic examination for the presence of casts and crystals, was performed daily on specimens collected 0 to 2 h after dosing. In addition, adverse events were recorded throughout the study. Blood and urine sampling. The blood samples (4 ml) used to assay for rufloxacin were collected via an indwelling venous catheter from a forearm vein just prior to the morning dose; at 1, 2, 2.5, 3, 3.5, 4, 6, 8, 10, and 12 h on day 1; and just before the morning dose on days 2 to 9. On the final treatment day (day 10), blood samples were obtained immediately before the morning dose and 1, 2, 2.5, 3, 3.5, 4, 8, 10, 12, 24, 48, 60, 72, 84, 96, and 120 h later. Plasma was prepared from each sample for subsequent assaying. Urine was collected at 0 to 2, 2 to 4, 4 to 8, 8 to 12, and 12 to 24 h on day 1 and at 24-h intervals thereafter up to day 9. On day
10, after the final dose, urine samples were collected at 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 48, 48 to 72, 72 to 96, and 96 to 120 h. Each sample was shaken, and after its volume was measured, a 20-ml aliquot was removed and frozen for later analysis. Assays. A modified version of the isocratic high-performance liquid chromatography technique described by Imbimbo et al. (7) was adopted. Rufloxacin and its main metabolite (the N-desmethyl derivative) were isolated from the plasma samples (250 ,ul) after the addition of 25 ,ul of a pipemidic acid solution (300 ,ug/ml) as the internal standard and following deproteinization with 70% perchloric acid. The percent recoveries were 73% for rufloxacin, 81% for the N-desmethyl derivative, and 92% for the internal standard. Seventy-five microliters of the isolated sample were injected onto a Beckman octyl (C8) Ultrasphere 5-pum-pore-size column (150 by 4.6 mm). The mobile phase was a ternary mixture of 0.017 M phosphoric acid, acetonitrile, and tetrahydrofuran (880/120/5 [vol/vol/vol]) adjusted to pH 5.0 with triethylamine. The column effluent was monitored by a fluorescence detector operating at an emission wavelength of 470 nm and an excitation wavelength of 360 nm. The linear range was 0.05 to 10 jig/ml for both rufloxacin and the N-desmethyl derivative. The limit of quantitation was 0.05 ,ug/ml for both rufloxacin and the N-desmethyl derivative. The interday coefficient of variation ranged from 3.9 (0.30 pug/ml) to 8.7% (0.15 ,ug/ml) for rufloxacin and from 2.7 (0.75 ,ug/ml) to 7.9% (0.15 ,ug/ml) for the N-desmethyl derivative. The intraday coefficient of variation ranged from 0.5 (0.75 ,ug/ml) to 5.5% (0.15 ,ug/ml) for rufloxacin and from 0.8 (0.75 ,ug/ml) to 5.6% (0.15 ,ug/ml) for the N-desmethyl derivative. Urine sample extractions were prepared after a mixture of phosphate salts and methylene chloride was added. The organic phase was dried down and reconstituted, and the effluent was monitored by fluorescence detection, with excitation at 360 nm and emission at 470 nm. The linear range was 0.05 to 50 ,ug/ml and the limit of quantitation was 0.05 ,ug/ml for both rufloxacin and the N-desmethyl derivative. The interday coefficient of variation ranged from 4.6 (15 jig/ml) to 6.0% (0.15 ,ug/ml) for rufloxacin and from 7.4 (15 ,ug/ml) to 9.8% (0.15 ,ug/ml) for the N-desmethyl derivative. The intraday coefficient of variation ranged from 3.2 (15 ,ug/ml) to 4.3% (2.5 ,ug/ml) for rufloxacin and from 2.8 (2.5 ,ug/ml) to 8.0% (0.15 ,ug/ml) for the N-desmethyl derivative. Pharmacokinetic analysis. Individual pharmacokinetic parameters were estimated with simultaneous fitting of all data points for each subject according to a one-compartment open model for repeated administration with lag-time and first-order input and output (3). This model corresponds to the following system of equations: C
=F =(ka Ct
TABLE 1. Demographic characteristics of the two groups Variable
Sex
Age (yr) Weight (kg) Serum creatinine (mg/dl) Creatinine clearance (ml/min)
Values for: 400-mg 600-mg group group
16 M, 0 F 25.0 ± 1.1 77.4 ± 2.3 1.31 ± 0.3 93 ± 3
16 M, 26.8 ± 74.6 ± 1.34 + 93 ±
0F 1.4 2.5 0.02 2
P
NS NS NS NS NS
1297
ka(t -t1ag) for t -1tag) -k( ke (t-t~) Ve
DL ka [ 1e -~[ -ke(t -
=
=(kaF
DL -
ka
*V [
ke)
F DM ka [(1
(ka -ke)
V
[(1
- ke(t
tiag)
_ e
ka(t - t
< 24 h
+ag)+
e- nkeT) -
keT)
(1 -enk,,T) (1
-
e
for t . 24 h ekaTe- Q8ss - t1ag) frt>2 -kT)_
in which C, is the estimated concentration in plasma of rufloxacin at time t (in hours), F is the fraction of the dose
ANTr'MIcRoB. AGENTS CHEMOTHER.
KISICKI ET AL.
1298
8z
7-
c-
6-
0 600 mg then 300 mg
z
OE
5-
CD)
4-
I
+l
0
=
3-
-J
! I
I
2-
400 mg then 200 mg
IL
1T 0
1
2
3
4
5
6
7
8
9
10
11
I
I
I
12
13
14
15
16
TREATMENT DAY FIG. 2. Mean (t standard deviation) concentrations in plasma of rufloxacin during two different repeated oral schedules, the first with a single oral loading dose of 400 mg followed by a single daily dose of 200 mg for 9 days (open squares) and the second with a single oral loading dose of 600 mg followed by a single oral daily dose of 300 mg for 9 days (closed squares). Arrows indicate when the drug was administered.
absorbed, V is the volume of distribution, DL is the loading dose (400 or 600 mg), DM is the maintenance dose (200 or 300 mg), n is the number of doses, X is the dosing interval (24 h), ka is the constant rate of absorption, ke is the constant rate of elimination, s is the time since the last dose [s = t - (n 1) T1 and tIag is the lag time. This model was selected with the Ip index (8). Nonlinear regression analysis was performed with the program TOPFIT (6). The area under the plasma concentration-time curve from zero to infinity (AUC_O) was calculated for the first administration as F DLI(V ke). The absorption half-life (t1/21) was calculated as ln(2)/ka, and the elimination half-life (t1/2) was calculated as ln(2)/ke. The mean residence time was calculated as (ka + ke)/ka k,. The apparent total body clearance (CL/F) was calculated as V ke, assuming complete bioavailability. The maximum plasma drug concentration after the initial dose (Cmax) and the final dose (Cmaxss) and the time to reach these concentrations (Tmax and TmaxSs) were obtained from the individual data. The areas under the plasma concentrationtime curve from 0 to 24 h after the first administration (AUCO24) and the final administration (AUCO24Ss) were calculated by the linear trapezoidal rule. The renal clearance after the first dose (CLR) was calculated by dividing the amount of drug excreted in urine in the 24 h after the first administration by the AUCO24. The renal clearance at the steady state (CLRss) was calculated by dividing the amount of the drug excreted in urine in the 24 h following the last dose by the AUCO24Ss. The percentage of drug excreted in
urine (fe) was calculated by dividing the total amount excreted in urine up to 120 h after the last administration by the total amount of drug administered during the treatment. The extent of accumulation (R) was calculated by dividing the AUCO24SS by the AUCO24 after correcting for the dose (2). Standard pharmacokinetic symbols were adopted. Statistics. Subject demographic characteristics and pharmacokinetic parameters of the two dose regimens were compared either by a Student t test for unpaired data or by the Mann-Whitney U test. Incidences of adverse effects in subjects taking placebos and in those taking the low- and the high-dosage regimen of rufloxacin were compared with the asymptomatic modification of Fisher's exact test (10). Statistical significance was defined as P < 0.05 (two-sided test). Calculations were made with the NWA STATPAK (11) and STATXACT (4) statistical packages.
RESULTS Plasma. The mean (± standard deviation) concentrations in plasma of rufloxacin, during and after drug administration, for the 400-mg and 600-mg groups are shown in Fig. 2. Drug concentrations greater than 2 ,ug/ml, a value equal to the MICs for most of the susceptible bacteria (9, 13), were achieved after the first dose with both dose regimens and were maintained for 48 h after the last administration. After the initial administration, mean Cmax was 3.35 + 0.12 ,ug/ml in the 400-mg group and 4.54 ± 0.19 ,ug/ml in the 600-mg
VOL. 36, 1992
PHARMACOKINETICS AND SAFETY OF RUFLOXACIN
1299
TABLE 2. Pharmacokinetic parameters for rufloxacin Values for: Parameter
tiag (min) tI/2a. (min) tmax (h)
Cmax (Pg/mi) CmaXS (pg/ml) t112 (h)
tmaXSS (h)
MRT" (h)
VIF (liters) CL/F (ml/min) CLR (ml/min)
CLRsS (ml/min) AUCO-24 (lg. h/ml)
AUCO-24SS (p,g h/ml) AUC()O, (pLg. h/ml)b R
fe (%) r1)
400-mg group Mean
SEM
29
7
5
1
1.9 3.35 2.3 4.51 40.0 57.8 132 39 21 18 56.5 87.0 176.1 3.1 49.6 0.997
0.2 0.12 0.3 0.15 1.5 2.2 4 1 1 1 1.5 3.1 6.3 0.1 1.3 0.001
P
600-mg group Range
Mean
SEM
Range
0-56
52
2
30-59
3-20 14
9
2
3-21
2.75-4.45 1.0-6.0 3.54-5.95 28.1-52.0 40.6-75.0 103-159 29-50 15-34 11-29 49.0-67.3 64.4-112.6 133.6-228.5 2.3-3.8 38.5-59.5
0.992-0.999
2.6 4.54 2.8 7.20 44.0 63.7 139 37 22 20 80.1 137.9 277.2 3.5 51.1 0.995
0.3 0.19 0.6 0.25 1.3 1.8 5 1 2 2 2.4 4.7 9.5 0.1 2.1 0.001
1-6 3.37-6.37 1.0-10.0 5.69-9.97 36.8-54.0 53.2-77.9 109-177 25-44 16-37 11-33 64.5-104.8 111.3-197.6 226.1-399.8 1.8-4.1
36.9-70.9 0.985-0.999
AND
CHEMOTHERAPY, June 1992, p. 1296-1301
Vol. 36, No. 6
0066-4804/92/061296-06$02.00/0
Multiple-Dose Pharmacokinetics and Safety of Rufloxacin in Normal Volunteers JAMES C. KISICKI,1 RHONDA S. GRIESS,1 CHRISTOPHER L. 0OT,' GUY M. COHEN,2 ROBERT J. McCORMACK,2 WILLIAM M. TROETEL,2 AND BRUNO P. IMBIMBO3* Harris Laboratories, Lincoln, Nebraska 685011; Oxford Research Intemnational, Clifton, New Jersey 07013-42212; and Mediolanum Farnaceutici, Milan, Italy3 Received 16 October 1991/Accepted 6 April 1992
The pharmacokinetics and safety of rufloxacin were evaluated in a double-blind, placebo-controlled study. Two groups of 16 healthy volunteers were given a single oral loading dose of 400 or 600 mg of rufloxacin on day 1 of the study. A single daily maintenance dose of 200 or 300 mg was then administered for a further 9 days; in addition, four subjects in each group received placebos. Rufloxacin levels in plasma and urine were determined by high-performance liquid chromatography. Following the initial dose, the mean (± standard 0.12 ,g/ml in the 400-mg group error of the mean) peak concentrations of rufloxacin in plasma were 3.35 and 4.54 + 0.19 pLglml in the 600-mg group. They were generaly reached 2 to 3 h after dosing. At the end of treatment, maximum levels in plasma rose to 4.51 ± 0.15 and 7.20 ± 0.25 pLg/ml in the 400-mg and 600-mg groups, with a mean extent of accumulation (fold) of 3.1 ± 0.1 and 3.3 ± 0.1. For the 400-mg and 600-mg groups, the elimination half-lives were 40.0 ± 1.5 and 44.0 ± 1.3 h, mean residence times were 57.8 ± 2.2 and 63.7 ± 1.8 h, apparent volumes of distribution were 132 ± 4 and 139 ± 5 liters, and apparent total body clearances were 39 ± 1 and 44 ± 4 ml/min, assuming complete bioavailability. Of the total dose administered, the percentages excreted in urine were 49.6 ± 1.3 and 51.1 ± 2.1%, with renal clearances of 21 ± 1 and 22 ± 2 ml/min, for the 400-mg and 600-mg groups. On the whole, the treatments were well tolerated, but some minor adverse events (mainly headache, insomnia, or abdominal discomfort) were reported for 7 subjects on the low-dose regimen, for 12 subjects on the high-dose regimen, and for 3 subjects taking placebos. No abnormalities were detected in the laboratory examinations or in ocular function tests. This study shows that a 200-mg daily oral dose of rufloxacin preceded by a loading dose of 400 mg are well tolerated and produce steady-state concentrations in plasma above the MIC for most susceptible pathogens. 9 days (the 600-mg group). Four subjects in each group received placebos in a double-blind fashion. Each dose was taken with about 50 ml of water at about 7:00 a.m. after an overnight fast. Fasting was continued for a further 2 h after the administration of the drug. At 9:00 a.m., a standardized breakfast of 700 kcal (ca. 3,000 kJ) was consumed. Breakfast generally consisted in two eggs with two bacon strips or two sausage links, two slices of toast with margarine and jelly or syrup, 6 oz (ca. 180 ml) of juice, and 8 oz (ca. 240 ml) of milk or coffee. A standardized lunch (1,000 kcal [ca. 4,000 kJJ) was given at 12:00 noon. Water was given ab libitum. All volunteers were outpatients. During sample collection periods and fasting periods, volunteers recovered in the Harris Laboratories Clinical Research Unit, Lincoln, Nebr. Subjects. Forty healthy male subjects completed this study: 32 were Caucasian, 3 were Black, 3 were Asian, 1 was Hispanic, and 1 was Indian. Demographic characteristics of the two treatment groups did not differ significantly (Table 1). All subjects were judged to be in good health as determined by physical examination, complete ophthalmological examination, electrocardiogram, full blood count, coagulation tests, serum chemistry profiles, and complete urinalysis. None of the subjects had a history of serious systemic illness, drug or alcohol abuse, or hypersensitivity to any food or drug. All subjects gave written informed consent before entering the study. The protocol of the study was approved by the Harris Laboratories Institutional Review Board. Safety evaluation. An extensive series of tests was carried out on every subject during each dosing period. Physical examinations were performed during preselection and at the
Rufloxacin is a new quinolone antibacterial agent (1) (Fig. 1). This drug has been shown to possess marked in vitro and in vivo activity against gram-negative and gram-positive bacteria (9, 13). Single-dose pharmacokinetic studies in normal volunteers showed that an oral dose of 400 mg of rufloxacin is eliminated slowly, with a plasma half-life of 30 to 40 h (7, 15). The study described here was designed to evaluate the pharmacokinetics and safety of multiple oral doses of rufloxacin. The results of this study should lead to the formulation of appropriate dosage regimens for the treatment of infectious diseases caused by rufloxacin-susceptible organisms. (Part of this work was presented at the 17th International Congress of Chemotherapy, Berlin, 23 to 28 June 1991 [abstract 379].)
MATERIALS AND METHODS Study design. Forty healthy male volunteers were randomly divided into two groups of 20 subjects. Rufloxacin (Mediolanum Farmaceutici, Milan, Italy) capsules were prepared by the Division of Pharmaceutical Service, College of Pharmacy, The University of Iowa. In the first group, 16 subjects were given a single loading dose of 400 mg (two capsules of 200 mg) on day 1 and single doses of 200 mg (one capsule) on the subsequent 9 days (the 400-mg group). In the second group, 16 subjects were given a single loading dose of 600 mg (four capsules of 150 mg) on the first day and single doses of 300 mg (two capsules of 150 mg) on the subsequent *
Corresponding author. 1296
VOL. 36, 1992
PHARMACOKINETICS AND SAFETY OF RUFLOXACIN
FIG. 1. Structural formula of rufloxacin.
end of treatment. Vital signs were monitored every day. Electrocardiograms were performed during preselection and 24 h after the last dose. Complete ophthalmological examinations, including visual acuity, slit lamp examination, funduscopic examination, Farnsworth hue color test, and electroretinogram, were carried out during preselection and 24 h after the last dose. Hematological tests (hemoglobin, hematocrit, erythrocyte count, leukocyte count, neutrophils, lymphocytes, eosinophils, basophils, monocytes, and platelets), coagulation tests (prothrombin time, activated partial thromboplastin time, and bleeding time), and chemistry profiles of serum (fasting blood glucose, urea nitrogen, sodium, potassium, chloride, carbon dioxide, magnesium, serum creatinine, uric acid, calcium, inorganic phosphorus, cholesterol, high-density lipoproteins, tryglycerides, total protein, albumin, globulin, total bilirubin, direct bilirubin, serum aspartate aminotransferase, serum alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, creatinine phosphokinase, and lactate dehydrogenase) were performed during the preselection phase and repeated each morning before the compound was administered on days 1, 2, 5, and 8 and 24 h after the last dose. Creatinine clearance rates were determined at preselection and after the final dose. Urinalysis, with microscopic examination for the presence of casts and crystals, was performed daily on specimens collected 0 to 2 h after dosing. In addition, adverse events were recorded throughout the study. Blood and urine sampling. The blood samples (4 ml) used to assay for rufloxacin were collected via an indwelling venous catheter from a forearm vein just prior to the morning dose; at 1, 2, 2.5, 3, 3.5, 4, 6, 8, 10, and 12 h on day 1; and just before the morning dose on days 2 to 9. On the final treatment day (day 10), blood samples were obtained immediately before the morning dose and 1, 2, 2.5, 3, 3.5, 4, 8, 10, 12, 24, 48, 60, 72, 84, 96, and 120 h later. Plasma was prepared from each sample for subsequent assaying. Urine was collected at 0 to 2, 2 to 4, 4 to 8, 8 to 12, and 12 to 24 h on day 1 and at 24-h intervals thereafter up to day 9. On day
10, after the final dose, urine samples were collected at 0 to 2, 2 to 4, 4 to 8, 8 to 12, 12 to 24, 24 to 48, 48 to 72, 72 to 96, and 96 to 120 h. Each sample was shaken, and after its volume was measured, a 20-ml aliquot was removed and frozen for later analysis. Assays. A modified version of the isocratic high-performance liquid chromatography technique described by Imbimbo et al. (7) was adopted. Rufloxacin and its main metabolite (the N-desmethyl derivative) were isolated from the plasma samples (250 ,ul) after the addition of 25 ,ul of a pipemidic acid solution (300 ,ug/ml) as the internal standard and following deproteinization with 70% perchloric acid. The percent recoveries were 73% for rufloxacin, 81% for the N-desmethyl derivative, and 92% for the internal standard. Seventy-five microliters of the isolated sample were injected onto a Beckman octyl (C8) Ultrasphere 5-pum-pore-size column (150 by 4.6 mm). The mobile phase was a ternary mixture of 0.017 M phosphoric acid, acetonitrile, and tetrahydrofuran (880/120/5 [vol/vol/vol]) adjusted to pH 5.0 with triethylamine. The column effluent was monitored by a fluorescence detector operating at an emission wavelength of 470 nm and an excitation wavelength of 360 nm. The linear range was 0.05 to 10 jig/ml for both rufloxacin and the N-desmethyl derivative. The limit of quantitation was 0.05 ,ug/ml for both rufloxacin and the N-desmethyl derivative. The interday coefficient of variation ranged from 3.9 (0.30 pug/ml) to 8.7% (0.15 ,ug/ml) for rufloxacin and from 2.7 (0.75 ,ug/ml) to 7.9% (0.15 ,ug/ml) for the N-desmethyl derivative. The intraday coefficient of variation ranged from 0.5 (0.75 ,ug/ml) to 5.5% (0.15 ,ug/ml) for rufloxacin and from 0.8 (0.75 ,ug/ml) to 5.6% (0.15 ,ug/ml) for the N-desmethyl derivative. Urine sample extractions were prepared after a mixture of phosphate salts and methylene chloride was added. The organic phase was dried down and reconstituted, and the effluent was monitored by fluorescence detection, with excitation at 360 nm and emission at 470 nm. The linear range was 0.05 to 50 ,ug/ml and the limit of quantitation was 0.05 ,ug/ml for both rufloxacin and the N-desmethyl derivative. The interday coefficient of variation ranged from 4.6 (15 jig/ml) to 6.0% (0.15 ,ug/ml) for rufloxacin and from 7.4 (15 ,ug/ml) to 9.8% (0.15 ,ug/ml) for the N-desmethyl derivative. The intraday coefficient of variation ranged from 3.2 (15 ,ug/ml) to 4.3% (2.5 ,ug/ml) for rufloxacin and from 2.8 (2.5 ,ug/ml) to 8.0% (0.15 ,ug/ml) for the N-desmethyl derivative. Pharmacokinetic analysis. Individual pharmacokinetic parameters were estimated with simultaneous fitting of all data points for each subject according to a one-compartment open model for repeated administration with lag-time and first-order input and output (3). This model corresponds to the following system of equations: C
=F =(ka Ct
TABLE 1. Demographic characteristics of the two groups Variable
Sex
Age (yr) Weight (kg) Serum creatinine (mg/dl) Creatinine clearance (ml/min)
Values for: 400-mg 600-mg group group
16 M, 0 F 25.0 ± 1.1 77.4 ± 2.3 1.31 ± 0.3 93 ± 3
16 M, 26.8 ± 74.6 ± 1.34 + 93 ±
0F 1.4 2.5 0.02 2
P
NS NS NS NS NS
1297
ka(t -t1ag) for t -1tag) -k( ke (t-t~) Ve
DL ka [ 1e -~[ -ke(t -
=
=(kaF
DL -
ka
*V [
ke)
F DM ka [(1
(ka -ke)
V
[(1
- ke(t
tiag)
_ e
ka(t - t
< 24 h
+ag)+
e- nkeT) -
keT)
(1 -enk,,T) (1
-
e
for t . 24 h ekaTe- Q8ss - t1ag) frt>2 -kT)_
in which C, is the estimated concentration in plasma of rufloxacin at time t (in hours), F is the fraction of the dose
ANTr'MIcRoB. AGENTS CHEMOTHER.
KISICKI ET AL.
1298
8z
7-
c-
6-
0 600 mg then 300 mg
z
OE
5-
CD)
4-
I
+l
0
=
3-
-J
! I
I
2-
400 mg then 200 mg
IL
1T 0
1
2
3
4
5
6
7
8
9
10
11
I
I
I
12
13
14
15
16
TREATMENT DAY FIG. 2. Mean (t standard deviation) concentrations in plasma of rufloxacin during two different repeated oral schedules, the first with a single oral loading dose of 400 mg followed by a single daily dose of 200 mg for 9 days (open squares) and the second with a single oral loading dose of 600 mg followed by a single oral daily dose of 300 mg for 9 days (closed squares). Arrows indicate when the drug was administered.
absorbed, V is the volume of distribution, DL is the loading dose (400 or 600 mg), DM is the maintenance dose (200 or 300 mg), n is the number of doses, X is the dosing interval (24 h), ka is the constant rate of absorption, ke is the constant rate of elimination, s is the time since the last dose [s = t - (n 1) T1 and tIag is the lag time. This model was selected with the Ip index (8). Nonlinear regression analysis was performed with the program TOPFIT (6). The area under the plasma concentration-time curve from zero to infinity (AUC_O) was calculated for the first administration as F DLI(V ke). The absorption half-life (t1/21) was calculated as ln(2)/ka, and the elimination half-life (t1/2) was calculated as ln(2)/ke. The mean residence time was calculated as (ka + ke)/ka k,. The apparent total body clearance (CL/F) was calculated as V ke, assuming complete bioavailability. The maximum plasma drug concentration after the initial dose (Cmax) and the final dose (Cmaxss) and the time to reach these concentrations (Tmax and TmaxSs) were obtained from the individual data. The areas under the plasma concentrationtime curve from 0 to 24 h after the first administration (AUCO24) and the final administration (AUCO24Ss) were calculated by the linear trapezoidal rule. The renal clearance after the first dose (CLR) was calculated by dividing the amount of drug excreted in urine in the 24 h after the first administration by the AUCO24. The renal clearance at the steady state (CLRss) was calculated by dividing the amount of the drug excreted in urine in the 24 h following the last dose by the AUCO24Ss. The percentage of drug excreted in
urine (fe) was calculated by dividing the total amount excreted in urine up to 120 h after the last administration by the total amount of drug administered during the treatment. The extent of accumulation (R) was calculated by dividing the AUCO24SS by the AUCO24 after correcting for the dose (2). Standard pharmacokinetic symbols were adopted. Statistics. Subject demographic characteristics and pharmacokinetic parameters of the two dose regimens were compared either by a Student t test for unpaired data or by the Mann-Whitney U test. Incidences of adverse effects in subjects taking placebos and in those taking the low- and the high-dosage regimen of rufloxacin were compared with the asymptomatic modification of Fisher's exact test (10). Statistical significance was defined as P < 0.05 (two-sided test). Calculations were made with the NWA STATPAK (11) and STATXACT (4) statistical packages.
RESULTS Plasma. The mean (± standard deviation) concentrations in plasma of rufloxacin, during and after drug administration, for the 400-mg and 600-mg groups are shown in Fig. 2. Drug concentrations greater than 2 ,ug/ml, a value equal to the MICs for most of the susceptible bacteria (9, 13), were achieved after the first dose with both dose regimens and were maintained for 48 h after the last administration. After the initial administration, mean Cmax was 3.35 + 0.12 ,ug/ml in the 400-mg group and 4.54 ± 0.19 ,ug/ml in the 600-mg
VOL. 36, 1992
PHARMACOKINETICS AND SAFETY OF RUFLOXACIN
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TABLE 2. Pharmacokinetic parameters for rufloxacin Values for: Parameter
tiag (min) tI/2a. (min) tmax (h)
Cmax (Pg/mi) CmaXS (pg/ml) t112 (h)
tmaXSS (h)
MRT" (h)
VIF (liters) CL/F (ml/min) CLR (ml/min)
CLRsS (ml/min) AUCO-24 (lg. h/ml)
AUCO-24SS (p,g h/ml) AUC()O, (pLg. h/ml)b R
fe (%) r1)
400-mg group Mean
SEM
29
7
5
1
1.9 3.35 2.3 4.51 40.0 57.8 132 39 21 18 56.5 87.0 176.1 3.1 49.6 0.997
0.2 0.12 0.3 0.15 1.5 2.2 4 1 1 1 1.5 3.1 6.3 0.1 1.3 0.001
P
600-mg group Range
Mean
SEM
Range
0-56
52
2
30-59
3-20 14
9
2
3-21
2.75-4.45 1.0-6.0 3.54-5.95 28.1-52.0 40.6-75.0 103-159 29-50 15-34 11-29 49.0-67.3 64.4-112.6 133.6-228.5 2.3-3.8 38.5-59.5
0.992-0.999
2.6 4.54 2.8 7.20 44.0 63.7 139 37 22 20 80.1 137.9 277.2 3.5 51.1 0.995
0.3 0.19 0.6 0.25 1.3 1.8 5 1 2 2 2.4 4.7 9.5 0.1 2.1 0.001
1-6 3.37-6.37 1.0-10.0 5.69-9.97 36.8-54.0 53.2-77.9 109-177 25-44 16-37 11-33 64.5-104.8 111.3-197.6 226.1-399.8 1.8-4.1
36.9-70.9 0.985-0.999
