Excretion Data for Cefazolin and Cephalothin After Intravenous and Intramuscular Administration in Humans

Transcription

1 ANTIMICROBIAL AGENT AND CHEMOTHERAPY, May 1975, p Copyright American Society for Microbiology Vol. 7, No. 5 Printed in USA. Pharmacokinetic Interpretation of Blood Levels and Urinary Excretion Data for Cefaolin and Cephalothin After Intravenous and Intramuscular Administration in Humans ELISABETH S. RATTIE AND LOUIS J. RAVIN* Research and Development Division, Smith Kline & French Laboratories, Philadelphia, Pennsylvania Received for publication 6 September 1974 Blood levels of cefaolin and cephalothin were determined in two separate crossover studies in 20 healthy male adults, each after intravenous and intramuscular administration. Pharmacokinetic parameters were calculated from the intravenous data based upon a two-compartment open model. The rate constants controlling the distribution between the central and peripheral compartments, the overall elimination rate constants, the apparent volumes of distribution, and the fraction of the dose in the central and peripheral compartments were determined. The bioavailability was calculated to be 100% for cefaolin and cephalothin. Cefaolin is a new broad-spectrum cephalosporin antibiotic derived from 7-amino cephalosporanic acid, which has a wide range of activity against gram-positive and gram-negative pathogens. It was synthesied and studied extensively in Japan (6, 11-13, 16) before being developed for clinical use in the United States. Pharmacokinetic studies in normal subjects have shown higher and more prolonged serum levels with cefaolin than with other cephalosporin antibiotics, e.g., cephaloridine and cephalothin (3, 11, 16, 17). While the drugs were under clinical investigation at Smith Kline & French Laboratories, a series of studies were undertaken to obtain additional human pharmacology data on cefaolin and compare it with cephalothin (2). It is the purpose of this paper to interpret the collected pharmacological data from these studies and to determine the pharmacokinetic parameters for cefaolin and cephalothin after 1-g intravenous and intramuscular injections. These parameters are important in evaluating pharmacokinetic differences within the cephaloporin class compounds, such as absorption and elimination rates, biological half-lives, serum-tissue distribution, distribution volumes, metabolic and renal clearance rates, and bioavailability. MATERIALS AND METHODS Crossover studies of cefaolin (Ancef; Smith Kline & French Laboratories) and cephalothin (Keflin; Eli Lilly & Co.) were carried out on two different groups of volunteers ranging in age from 21 to 42 years and weighing between 125 and 220 lb. (about 56.6 and 99.7 kg, respectively). They were selected on the basis of a 606 complete medical history to exclude those having a history of hematologic, hepatic, or renal disease and those with a history of allergic sensitivity to penicillins and cephalosporins. One group of 20 healthy males participated in the intravenous comparative study of cefaolin and cephalothin; the second group participated in the intramuscular study. On the first test day in each study, 10 subjects 1 g of cefaolin by injection and the other 10 received 1 g of cephalothin. On the second test day (72 h later), cefaolin was given to the test subjects who had received cephalothin, and vice versa. Cefaolin and cephalothin vials were reconstituted with water for injection, USP, before administration. Blood specimens were collected at 0 h and at 5, 15, 30, 60, 120, and 240 min after intravenous injection. Blood specimens were collected at 0, 0.5, 2, 4, 6, 8, 10, and 12 h after intramuscular injection. Urine was collected at pre-drug time, 0 to 2, 2 to 4, 4 to 6, and 6 to 12 h after intravenous injection and at pre-drug time, 0 to 2, 2 to 4, 4 to 6, 6 to 12, and 12 to 24 h after intramuscular injection. Blood and urine samples were collected, froen, and then analyed for drug concentration by a Bacillus subtilis agar disk plate method (5). RESULTS Intravenous administration. Semilog plots of average serum levels of cefaolin (17 subjects) and cephalothin (20 subjects) after a 1-g intravenous injection versus time are shown in Fig. 1 and 2. The averages are a good representation of the data of all individual subjects. Pharmacokinetic analysis was carried out on all individual subjects; the average parameters calculated were very close to the parameters calculated from the plots of average drug levels in the serum so that the parameters used for the discussion in this paper will be those calculated

2 VOL. 7, 1975 COMPARISONS OF CEFAZOLIN AND CEPHALOTHIN 607 from plots of average drug levels in the serum. Figures 1 and 2 show the serum levels for cefaolin and cephalothin declining in a biexponential manner after intravenous administration. The date could therefore be mathemati- CEPHALOTHIN - INTRAVENOUS cally fitted with a two-compartmental open 1000 mg system (9, 15). Such a model is illustrated 100 below: drug in blood (Dp) k12 drug in tissues (Di) k2l~~~~~~~~~ drug eliminated (Du) Dp is the amount of intact drug in the central locompartment, D, is the amount of drug in the, peripheral compartment, k12 and k21 are the first-order distribution rate constants controlling diffusion of drug between the two compartments, and kei is the sum of the first-order rate constants responsible for metabolism and excretion. The serum level time curves represented in Fig. 1 and 2 can thus be described by the following biexponential equation: TIME (minutes) C= Aeat + Be-t FIG. 2. Serum levels after a 1-g intravenous injecand at ero time Cp = A + B (1) tion of cephalothin (open circles); average of 20 subjects. The differences between the,8-phase line where Cp is the concentration of the drug in the and the serum levels at 5, 15, and 30 min are represented by the solid circles. Solid line is the computergenerated curve. CEFAZOLIN - INTRAVENOUS 1000 mg plasma, Cpo is the extrapolated ero-time plasma concentration of drug, and A, B, a, and i, are constants and can be determined by "feathering" the biexponential curve. Average values for C,, A, B, a, and,b for cefaolin and 100 ) cephalothin are listed in Table 1. The solid lines in Fig. 1 and 2 were calculated by using the x.' )<constants obtained by feathering. There was excellent agreement between the theoretical and actual data for both compounds. The area under the serum level time curve ' \ can be calculated by the equation 10 A B area=- +- (2) a d The areas thus calculated for cefaolin and cephalothin are also listed in Table 1 and are in close agreement with the areas determined graphically by the trapeoidal rule. Since A, B, I_ 20,0, a, and # are constants and each one is in fluenced by all of the constants of the TIME (min.) the individual rate constants can be calculated system, FIG. 1. Serum levels after a 1-g intravenous injec- from equations 3, 4, and 5 (15): tion of cefaolin (open circles); average of 17 subjects. The differences between the a-phase line and the k Cp9 (3) serum levels at 5, 15, and 30 min are represented by el= A B the solid circles. Solid line is the computer-generated + - curve. a,

3 608 RATTIE AND RAVIN _2= a- (4) kei k2 =a + - k2i kel - (5) The individual rate constants for cefaolin and cephalothin and the,b-phase half-lives (commonly termed "biological half-lives") are listed in Table 2. The rate constants k,, and k21 in Table 2 were greater for cefaolin than for cephalothin, and the elimination rate constant was approximately three times less for cefaolin. than for cephalothin. The serum-tissue distribution of cefaoliri and cephalothin can be estimated by calculating the fraction of the administered intravenous dose in the peripheral and central compartments at various times. The fraction in the peripheral and central compartments can be calculated from equations 6 and 7, respectively, arid the parameters listed in Tables 1 and 2 (15): A = (e-t e-at) ay- (6) AC= [(a ) e-at + ( k2 es] (7) Figures 3 and 4 show plots of fractional serumtissue distributions for cefaolin (average of 17 subjects) and cephalothin (average of 20 subjects) versus time along with the standard deviations after a 1-g intravenous injection. Similar plots were obtained for all individual subjects. In all cases, the amount of cefaolin in the tissue compartment peaked at 20 to 33% of the administered dose, cephalothin peaked at 7 to 12%, and the drug levels in plasma and tissue then decreased in a parallel fashion as expected. Urinary recoveries of cefaolin and cephalothin after intravenous administration in a time period of 0 to 12 were 75.5 and 37.5%, respectively. Nicholas et al. (10) and Kirby et al. (14) TABLE 1. am 0 am. I2 ANTIMICROB. AGENTS C1jEMoTHER. have demonstrated that the entire dose of cefaolin is excreted during a 24-h time period after intravenous and intramuscular administration and that at least 90% of the given dose is excreted during the first 8 h. Nishida et al. (13) have also demonstrated that the active substance in the urine is unchanged cefaolin and that approximately 3.3% is excreted in the bile. On the other hand, approximately 35% of the TABLE 2. Individual rate constants for the two-compartment open mqdel Drug k,2 (h-') k,, (h-'), ke,(h-) (h) Cefaolin Cephalothin ; CEFAZOLIN TIME (minuts) FIG. 3. Percent of cefaolin dose estimated in the peripheral compartment (solid circles) and in the central compartment (open circles) after a 1-g intravenous injection of cefaolin. (Average of 17 subjects.) Parameters of equation I Drug A B a (min- ) d (min ) p trapeoidal From equation 2 rule Fratom Area Cefaolin Cephalothin

4 VOL. 7, 1975 CEPHALOTHIN COMPARISONS OF CEFAZOLIN AND CEPHALOTHIN 609 LU o SUBJECT 1 a SUBJECT 2 * SUBJECT 6 4 SUBJECT 8 * AVERAGE 0a 01 I.-~~~~~ ies for cefaolin and cephalothin after a 1-g intravenous injection for all 20 subjects used in the study. The tremendous variation and irregularities in urinary collection are obvious. The volume of distribution, Vd,,, was calcu TIME (minutes) FIG. 4. Percent of cephalothin dose estimated in the peripheral compartment (solid circles) and in the central compartment (open circles) after a 1-g intravenous injection of cephalothin. (Average of 20 subjects.) administered dose of cephalothin is metabolied to desacetylcephalothin, which only has about 25% as much antibacterial activity as cephalothin (1). Kirby et al. (14) have found 52% cephalothin in a 24-h urine collection. Figures 5 and 6 show plots of percent urinary excretion of cefaolin and cephalothin, respectively, after a 1-g intravenous injection versus time. The solid lines were generated by a digital computer programed with a two-cqmpartment open model and the rate constants shown in Table 2. The experimental points for subjects 1, 2, 6, and 8 after a 1-g intravenous injection of cefaolin (Fig. 5) and the experimental points fqr subjects 12 and 15 after 1-g intravenous injection of cephalothin (Fig. 6) were in good agreement with the theoretical curve. The computer curve generated for cephalothin is based on 35% metabolite, desacetylcephalothin. However, the average urinary excretion values (averaged urinary excretion values of all 20 subjects) for both drugs were not in agreement with the theoretical values. The reason for this can be found in Table 3, which shows urinary recover- u x 0 Z / a 0o / TIME (hours) FIG. 5. Cefaolin activity levels in the urine after a 1-g intravenous injection. Solid circles are the average cefaolin activity levels of 20 subjects; the other points represent urine activity levels of 4 individual subjects selected from the group of 20. > SUBJECT 5 _U a 0 SUBJECT 12 SUBJECT 15 * AVERAGE x 4 Z 10Qo 80- U I 0>t0 0 C LU TIME (hours) FIG. 6. Cephalothin activity levels in the urine after a 1-g intravenous injection. Solid circles are the average cephalothin activity levels of 20 subjects; the other points represent urine activity levels of 3 individual subjects selected from the group of 20.

5 610 RATTIE AND RAVIN ANTIMICROB. AGENTS CHEMOTHER. Subject no. TABLE 3. Recovery of cefaolin and cephalothin in urine after a 1-g intravenous injection Cefaolin (mg) Cephalothin (mg) 0-2a Total Total Avg a Hours after administration. lated from the parameters of the two-compartment model by equation 8: Vss = kl2+ k2l 21I V p (8) The apparent volume of the extravascular tissue compartment, VT, was also estimated by subtracting the volume of the central compartment, Vp, from the apparent volume of the entire body compartment. The ratio VT/VP represents the ratio of the amount of the drug in the extravascular tissue compartment to the amount of drug in the central compartment. The parameters are listed in Table 4. Since serum protein binding is approximately 85% for cefaolin (14) and 65% for cephalothin (7), the apparent volume of distribution for cefaolin is also lower than that for cephalothin. The total clearance rates (TCR) for cefaolin and cephalothin were calculated from the pharmacokinetic parameters by using equation 9: TCR = kei Vp (9) and were 3.8 and 19.8 liters/h, respectively. The renal clearance rates (RCR) for cefaolin and cephalothin were calculated by using the fractions of the dose excreted in the urine (f) for subjects 1, 2, 6, and 8 for cefaolin and the fraction of the dose excreted in the urine for TABLE 4. Drug Cefaolin... Cephalothin... Volumes of distribution subjects 12 and 15 for cephalothin. These data were in agreement with the theoretical fractions of the dose excreted in the urine for cefaolin and cephalothin. The theoretical fractions were generated by a digital computer programed with a two-compartment open model and the rate constants shown in Table 2. The TCR for cefaolin and cephalothin were multiplied by the fractions of the dose excreted in the urine (f) according to equation 10: RCR = f.tcr = f.vp.kel (10) and the values were 3.6 and 10.3 liters/h, respectively. The total and renal clearance rates for cefaolin were almost identical and were consistent with the urinary recovery of almost 100% of administered dose in the urine for subjects 1, 2, 6, and 8. The high plasma and renal clearance rates for cephalothin can be attributed to active tubular secretion (7, 8) and the partial conversion of cephalothin to desacetylcephalothin, which also is responsible for

6 VOL. 7, 1975 approximately 60% urinary recovery of the administered dose found with subjects 12 and 15 and which has been demonstrated by Kirby et al. (14). These data are in -agreement with previously published results (10, 14). Intramuscular administration. A semilog plot of average serum levels of cefaolin and cephalothin in 19 subjects after a 1-g intramuscular injection versus time is shown in Fig. 7. Peak serum concentrations were attained at 1 h for cefaolin (59.0 ± 9.2,ug/ml) and 0.5 h for cephalothin (20.0 i 6.4,ug/ml) and were three times as high for cefaolin as for cephalothin. Although the serum level data fit a two-compartment open model, not enough blood samples were taken during the first 1.5 h, and therefore graphic dissection of the curves was not possible and absorption rate constants could not be calculated. The terminal data points on the serum concentration time plots were used to calculate the biological half-lives of cefaolin and cephalothin, and the mean halflives were found to be 119 and 43.5 min, respectively, after intramuscular administration. Tables 5 and 6 show the biological halflives for cefaolin and cephalothin after 1-g *1% ị 3t _ 2 COMPARISONS OF CEFAZOLIN AND CEPHALOTHIN 611 TABLE 5. Biological half-lives for cefaolin and cephalothin administered intravenouslv (1-g dose) Cefaolin Subject no. t", tm, Cephalothin mini min]/ (min-') [(0.69i min] (minm l) 1a a a Mean of all subjects standard deviation a Serum level data not available. o CEFAZOLIN intravenous and intramuscular administrations * CEPHALOTHIN for all subjects along with the mean and stan- INTRAMUSCULAR dard deviations mg The mean serum half-life of 39.3 min after intravenous injection of 1 g of cephalothin is comparable with that of 43.5 min found after intramuscular injection of the drug. In contrast, the mean serum half-life of 87 min after intravenous injection of lg of cefaolin compared with that of 119 min after intramuscular injection suggests that cefaolin, which is 85% protein bound, may be bound to proteinaceous muscle tissue, which may prolong its release from the site of injection. Similar results have been obtained with cephalexin (4). The areas under the serum level time curves were determined by the trapeoidal rule for cefaolin and cephalothin after intramuscular administration. For cefaoiin, the areas under the curves were ' nearly the same for the intravenous and intra ai TIME (hours) muscular serum levels time curves, indicating G. 7. Serum levels after a 1-g intramuscular 100%o availability. The availability for cephalo- FI4 injec tion of cefaolin and cephalothin. (Average of 19 thin was calculated to be 100% based on the subjeects.) urinary excretion data, although the blood 1ev-

7 612 RATTIE AND RAVIN ANTIMICROB. AGENTS CHEMOTHER. TABLE 6. Biological half-lives for cefaolin and els did not show this because the first point was cephalothin administered intramuscularly (1-g dose) collected at 0.5 h. The mean urinary excretion Cefaolin Cephalothin data for cefaolin and cephalothin are presented in Table 7. Subject no. t9 The urinary recovery of cephalothin after a min] (m-m i) 1-g intramuscular administration agreed well with the urinary excretion values found by Kirby et al. (14). Average urinary excretion values for cefaolin after a 1-g intramuscular administration did not agree with the theoreti cal values and those published in the literature Again, when we look at Table 7, which shows '.. ' urinary recoveries for cefaolin and cephalothin after a 1-g intramuscular injection for all subjects used in the study, we find tremendous 1311a variation between individual subjects who had received cefaolin. Some extremely low individ ual urinary excretion values were responsible for the lower average urinary collection DISCUSSION Intravenous and intramuscular comparative studies of cefaolin and cephalothin showed Mean of all that cefaolin produces significantly higher and subjects ± longer-lasting serum concentrations and that it standard is eliminated in the urine to a much greater deviation extent than cephalothin. Observed maximum a Subject 1311 was not available on test day 2. serum levels averaged and ug/ml TABLE 7. Recovery of cefaolin and cephalothin in urine after a 1-g intramuscular injection Subject Cefaolin (mg) Cephalothin (mg) no. 0-2a Total Total 1 NSb , NS , NS NS 290 NS NS 360 NS NS NS , , , NS NS NS NS NS NS NS Avg a Hours after administration. b NS, No sample.

8 VOL. 7, 1975 and 12-h urinary recoveries averaged 75.5 and 37.5% for cefaolin and cephalothin, respectively, after intravenous administration. Observed maximum serum levels averaged 59.0 and 20.0 gag/ml and 24-h urinary recoveries averaged 73.5 and 52% for cefaolin and cephalothin, respectively, after intramuscular administration. The serum and urine data were evaluated by calculating pharmacokinetic parameters that are commonly used as guides in establishing proper dosage regimens. The bioavailability was calculated to be 100% for both cefaolin and cephalothin. LITERATURE CITED 1. Benner, J Cephalosporin antibiotics: therapeutic discussions and future. Postgrad. Med. J. Suppl. 47: Cahn, M. M., E. J. Levy, P. Actor, and J. F. Pauls Comparative serum levels and urinary recovery of cefaolin, cephaloridine, and cephalothin in man. J. Clin. Pharmacol. 14: DeSchepper, P., C. Harvengt, V. Vranckx, B. Boon, and M. D. Lamy Pharmacologic study of cefaolin in volunteers. J. Clin. Pharmacol. 13: Gower, P. E., C. H. Dash, and C. H. O'Callaghan Serum and blood concentration of sodium cephalexin in man given single intramuscular and intravenous injections. J. Pharm. Pharmacol. 25: Grove, D. C., and W. A. Randall Assay methods of antibiotics: a laboratory manual. Medical Encyclopedia, Inc., New York. 6. Kariyone, K., M. Harada, and T. Takano Cefaolin, a new semisynthetic cephalosporin antibiotic. I. Synthesis and chemical properties of cefaolin. J. Antibiot. 23: Kirby, W. M. M., J. B. de Mame, and W. S. Serill Pharmacokinetics of the cephalosporins in healthy COMPARISONS OF CEFAZOLIN AND CEPHALOTHIN 613 volunteers and uremic patients. Postgrad. Med. J. 47: Lee, C. C., and R. C. Anderson Absorption, distribution, and excretion of a 1-a-phenoxypropyl, d-a-phenoxypropyl,dl-a-phenoxyethyl, and phenoxymethyl penicillins, p Antimicrob. Agents Chemother Mayersohn, M., and M. Gibaldi Mathematical methods in pharmacokinetics. II. Solution of the two compartment open model. Am. J. Pharm. Educ. 1: Nicholas, P., B. R. Meyers, and S. Z. Kirschman Pharmacology of cefaolin in human volunteers. J. Clin. Pharmacol. 13: Nishida, M., T. Matsubara, T. Mine, T. Yokata, S. Kuwahara, and S. Goto In vitro and in vivo evaluation of cefaolin, a new cephalosporin C derivative, p Antimicrob. Agents Chemother Nishida, M., T. Matsubara, T. Murakawa, Y. Mine, Y. Yokata, S. Goto, and S. Kuwahara Cefaolin, a new semisynthetic cephalosporin antibiotic. II. The in vitro and in vivo antimicrobial activity. J. Antibiot. 23: Nishida, M., T. Matsubara, T. Murakawa, Y. Mine, Y. Yokata, S. Goto, and S. Kuwahara Cefaolin, a new semisynthetic cephalosporin antibiotic. III. Absorption, excretion, and tissue distribution in parenteral administration. J. Antibiot. 23: Regamy, C., R. Gordon, and W. M. M. Kirby, Cefaolin versus cephalothin and cephaloridine. A comparison of their clinical pharmacology. Arch. Intern. Med. 133: Riegelman, S., J. C. K. Loo, and M. Rowland Shortcomings in pharmacokinetic analysis by conceiving the body to exhibit properties of a single compartment. J. Pharm. Sci. 57: Shubita, K., and M. Fugii Clinical studies of cefaolin in the surgical field, p Antimicrob. Agents Chemother Wick, W. E., and D. A. Preston Biological properties of three 3-heterocyclic-thiomethyl cephalosporin antibiotics. Antimicrob. Agents Chemother. 1: