Pharmacokinetics of Sulfisoxazole in Renal Transplant Patients

Transcription

1 ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Oct. 1985, p /85/1535-5$2./ Copyright 1985, American Society for Microbiology Vol. 28, No. 4 Pharmacokinetics of Sulfisoxaole in Renal Transplant Patients MARIA SHERMANTINE,'t JOHN GAMBERTOGLIO,' WILLIAM AMEND,2 FLAVIO VINCENTI,2 AND SVEIN IE1* Department of Pharmacy, School of Pharmacy,' and Department of Medicine, School of Medicine,2 University of California, San Francisco, California Received 19 April 1985/Accepted 24 July 1985 We studied the elimination of sulfisoxaole in eight renal transplant patients. The patients received sulfisoxaole prophylactically for urinary tract infection commencing 7 days postoperatively. The renal elimination of sulfisoxaole (unbound renal clearance) was decreased in this patient population and was highly correlated with creatinine clearance. The unbound metabolic clearance and apparent unbound formation clearance of N4-acetyl sulfisoxaole did not differ from values found in healthy volunteers. The protein binding was marginally lower in this patient population than in healthy subjects after a single dose. The reduced binding was compatible with a reduced albumin concentration. In contrast to the situation for healthy subjects, the binding of sulfisoxaole decreased upon multiple dosing. This is probably due to a relatively higher sulfisoxaole and N4-acetyl sulfisoxaole-to-albumin ratio in this patient population than in healthy subjects. No complications of sulfisoxaole therapy were seen, although in three subjects concentration of the N4-acetyl sulfisoxaole in urine exceeded its theoretical solubility on a few occasions. Sulfisoxaole is often used as a prophylactic antibacterial agent in renal transplant patients to reduce the likelihood of urinary tract infections during the postoperative recovery phase (2). Sulfisoxaole has been safely used in this patient population in a number of institutions including our own (3, 6). Several concerns exist regarding the use of sulfisoxaole in the transplant population. Renal function is generally lower than normal, which causes an increased risk of crystalluria. However, the risk is usually considered to be low (1), mainly owing to the high solubility of both sulfisoxaole and its primary metabolite N4-acetyl sulfisoxaole (13). Because of the reduced renal function, the fraction excreted unchanged in the urine is decreased and may compromise the effectiveness of therapy. Reidenberg et al. (11) have also suggested that the metabolism of sulfisoxaole may be decreased in subjects with decreased renal function. The mechanism for such a decrease is unclear, but data obtained with experimental animals have suggested that sulfisoxaole may be renally metabolied (4) and that decreased renal function may subsequently result in a decreased metabolic clearance. In addition, data obtained with experimental animals have suggested that N4-acetyl sulfisoxaole may inhibit its own formation (8, 9). Moreover, there is a reported decrease in the protein binding of sulfisoxaole in renal failure (14), which significantly affects both the clearance and distribution. This study was undertaken to evaluate the disposition and urinary excretion of sulfisoxaole and N4-acetyl sulfisoxaole in postrenal transplant patients being treated prophylactically with sulfisoxaole. MATERIALS AND METHODS Protocol. (i) Subjects. Six male and two female patients receiving cadaver kidney transplants were studied. The patients received 5 to 1, mg of sulfisoxaole (Gantrisin) orally two (b.i.d.) to four (q.i.d.) times per day, as prescribed by their primary care physician. Dose sie was generally * Corresponding author. t Present address: Mediphysics Inc., Richmond, CA based on 24-h creatinine clearance values. Treatment commenced approximately 7 days after the transplant, at which time the urinary catheter inserted during the surgery was removed. All patients studied had hematocrit values of > 2%, few had abnormal liver function tests, none had histories of allergy to sulfisoxaole, and none were given other antibiotics during the treatment period. Laboratory data for the eight patients are presented in Table 1. Four or five 4-ml blood samples were obtained during the first dosing interval after initiation of drug therapy and again during a dosing interval on days 4 and 7 after the start of therapy. At the 6-h dosing interval samples were obtained at, 2, 4, and 6 h, and at the 12-h dosing interval blood samples were obtained at, 2, 4, 8, and 12 h. The samples were obtained by venipuncture and allowed to clot, and the serum was separated by centrifugation at 7 x g for 2 min. The serum was collected and kept froen (-2 C) until assayed. Urine was collected every 2 h during the blood sampling periods; otherwise, the total daily urine was collected at 24-h intervals for the remainder of the hospital stay of each patient or until sulfisoxaole administration was discontinued. The urine volume and ph were determined for each urine sample, and a sample was stored froen (-2 C) until assayed. (ii) Normal volunteers. Six healthy male volunteers ranging in age from 23 to 34 years were studied. Sulfisoxaole disposition was determined after a 1,-mg single oral dose, during a 1,-mg intravenous bolus dose, and during a multiple dosing regimen of 5 mg q.i.d. The results for the normal volunteers have been presented in detail previously (1). Protein binding. A 1-ml portion of serum was placed in a Millipore 1-mm dialysis cell (xx ) equipped with a magnetic stirrer. Serum water was filtered through a 25,-MW cutoff filter (Millipore PSED) with nitrogen (pressure, 3.5 bar [3.5 x 15 Pa]) containing 1.4% CO (5 mbar [5 x 13 Pa]). The ultrafiltration was carried out at 37C. Two aliquots of 1 RI of serum filtrate each were collected and assayed for sulfisoxaole. The concentration of sulfisoxaole in the second 1-,u aliquot never exceeded Downloaded from on July 22, 218 by guest

2 536 SHERMANTINE ET AL. ANTIMICROB. AGENTS CHEMOTHER. TABLE 1. Clinical data from renal transplant patients Amt of: Subject Wt Age Creatinine Alka- Hematn. (g y)abmn (mg/dl) on day: Biliru- LH SO line ocrit Other drugs (gender ) (g/dl) bin (IUU/ID) (IU/ml)D phos- value (mg/dl) phatase (IU/ml) 1 (M) Prednisone, aathioprine, Maalox, Amphogel 2 (M) Prednisone, aathioprine, Maalox, Amphogel, insulin, Colace, fluraepam, methyldopa, furosemide, hydralaine, benopyridine 3 (F) Prednisone, aathiopine, Maalox, Amphogel 4 (M) Prednisone, aathioprine, Maalox, Amphogel S (M) Prednisone, aathioprine, Maalox, Amphogel, folate, furosemide, methyldopa, clonidine, kayexalate 6 (M) Prednisone, aathioprine, Maalox, Amphogel 7 (M) Prednisone, aathioprine, Maalox, Amphogel, propranolol, hydraloine 8 (F) Prednisone, aathioprine, Maalox, Amphogel, furosemide a LDH, lactate dehydrogenase; SGOT, serum glutamic oxalacetic transaminase. the first by more than 1%, and this aliquot was used for the reported serum water concentration of sulfisoxaole. Repeated determinations of the unbound fraction of sulfisoxaole in the samples yielded a coefficient of variation.42 (n = 22) in the normal subjects and.51 (n = 8) in the renal transplant patients. Assay methods. Sulfisoxaole and its major metabolite, N4-acetyl sulfisoxaole, in serum and urine were determined by a specific high-pressure liquid chromatographic method, described previously (7). Total sulfisoxaole (unchanged drug and metabolites) in urine was determined by hydrolysis of the urine samples with hydrochloric acid at 1 C as described by Rieder (12) together with the colorimetric assay method described by Bratton and Marshall (5) as modified by ie (9). Urine obtained from the individual patients before sulfixaol administration was used a blank. The coefficient of variation at 2 mg/ml was 2.3% (n = 9) with this procedure. Treatment of data. Treatment of the results from the healthy volunteers was described previously (1). The renal clearance values in the renal transplant patients were obtained by determining the total amount of drug collected in urine during the dosing interval divided by the area under the serum concentration-time curve for the same interval. The area was obtained by using the trapeoidal rule. The unbound clearance-bioavailability was obtained by dividing the administered dose per dosing interval by the area under the unbound serum concentration-time curve during the same interval. For the latter calculation we assumed that steadystate conditions had been reached. The formation clearance of N4-acetyl sulfisoxaole was determined by dividing the molar amount of N4-acetyl sulfisoxaole in urine by the area under the serum concentration-time curve of sulfisoxaole, expressed in molar concentrations. For this calculation we assumed that N4-acetyl sulfisoxaole was essentially eliminated in the urine as unchanged N4-acetyl sulfisoxaole and was metabolied further only to an insignificant degree. The unbound fraction value reported is the ratio of the area under the concentration-time curve in serum water (serum filtrate) to the area under the concentration-time curve in serum, and represents the time-averaged observed value. RESULTS A typical serum concentration-time plot of a representative patient is shown in Fig. 1. Average recovery from urine with time of sulfisoxaole, sulfisoxaole plus N4-acetyl sulfisoxaole, and total sulfisoxaole, is given in Fig. 2. Average concentrations of urine, their ranges and standard deviations, urine flow rate, and ph for the individual subjects are presented in Table 2. The unbound clearancebioavailability, of sulfisoxaole is given in Table 3, together with the unbound fraction values of sulfisoxaole over the three study days. The bioavailability of sulfisoxaole based on unbound drug in the normal control subjects was I.-- Uuj _ 1- f' A A/ I--,'..,* N \A A*/ I I t} 1 1 I I fk- I} I DAY 1 DAY 4 DAY 7 TIME, HOURS FIG. 1. Concentration of total () and unbound (A) sulfisoxaole and total () and unbound (A) N4-acetyl sulfisoxaole in the plasma of subject no. 3. Downloaded from on July 22, 218 by guest

3 VOL. 28, 1985 SULFIZOXAZOLE IN TRANSPLANT PATIENTS 537 C-, X: LLX r) I ' L' n.s w CZ).u,,,.66. F.4 U-.2, nine clearance (r2 =.86, t = 9.281, P <.1; see Fig. 3).. / The creatinine clearance reported was obtained within 1 day \_-\ of a study period.the time varied for each subject,but _._o *-_,-_usually.* corresponded to study day 4. In two subjects, *\, v creatinine clearance was determined in conjunction with two J * of the study periods; both are reported. The unbound fraction of sulfisoxaole was higher in the renal transplant patients than in the control subjects, both on day 1 and on the last study day (t = 2.489, P <.5, and t = _ * U 4.215, P <.1, respectively). The difference on day 1 *.-mnu/wf \ / appears to correspond to the difference in albumin concentration between these groups (3.8 versus 4.4 g/dl; t = 3.37, _/ * P <.1). Calculating nk from the relationship: f, nk. Pt), wheref, is the unbound fraction, = 1/(1 n is the number of + / A binding sites, K is the association constant for albumin- A * * sulfisoxaole, and P, is the albumin concentration, and _/* comparing the obtained values for nk between the groups, l /.*-*--* no differences could be found (t =.918, P >.3). This /,_-_ relationship is based on the assumption that only a small A* fraction of the albumin sites are occupied. The higher / unbound fraction on the last study day, on the other hand, cannot be explained by the albumin concentration difference l I I I I I I I alone, as a significant difference in nk values between the groups was found (t = 3.362, P <.1). TIME, DAYS The excretion of sulfisoxaole from urine, on average, appeared to increase with time. The increase seemed to Average recovery from urine with time of sulfisoxaole correspond to an improvement in the renal function, as nbined sulfisoxaole and N4-acetyl sulfisoxaole (A), evidenced by the decreasing creatinine concentration in FIG. 2 (), con and total sulfisoxaole determined by the Bratton-Marshall (5) serum with time. An exception appeared to occur between method ( <i). Average creatinine values in serum, calculated as days 6 and 1, when patient no. 6 experienced a n rejection nl/, (1/S'CR,), are plotted for comparison (-). period, resulting in a significantly increased creatinine level i=1 in serum. The excretion of sulfisoxaole from urine correlated with.4 (11 ). With the assumption that the bioavailability is the creatinine concentration in serum in only two of the similar lin renal transplant patients, the values in Table 3 transplant patients (no. 2 and 6; P <.25 by the Student t were tre, ated as the clearance values. test). The total unbound clearance (CLu), as well as the unbound renal clearance (CLuR), were statistically significantly lower in the transplant patients than in the control subjects (t DISCUSSION = 2.286, P <.5, and t = 3.199, P <.1, respectively). The elimination of sulfisoxaole (CLu) in renal transplant The unbound extrarenal clearance (CLuxR) and the unbound patients is similar to that found in normal subjects when formation clearance of N4-acetyl sulfisoxaole in the transplant patients were, on the other hand, not statistically There is no evidence of reduced metabolic elimination differences in renal function are taken into consideration. significantly different from the control values (t =.265, P > similar to that suggested by Reidenberg et al. (11) in renal.7, and t = 1.324, P >.2, respectively). The lower CLu failure subjects or to what was found in renal failure animals therefore seems to be a result of the decreased renal elimination of sulfisoxaole. The CLUR of sulfisoxaole in the reduced renal function in our patients compared with those (9a). This is probably a consequence of only a moderately study subjects correlated highly with the measured creati- in the other studies. Downloaded from on July 22, 218 by guest TABLE 2. Urinary concentrations' of sulfisoxaole and N4-acetyl sulfisoxaole, urine flow rate, and urine ph in renal transplant patients Subject Sulfisoxaole Concn (mg/liter) N4-acetyl sulfisoxaole Urinary flow Avg urine (no.) (mg/liter) Uriary fmloway Avpuin Dosage regimen (mg) Avg Range Avg Range 1 14 ± ± ,23 ± ±.21 Day 1,2: 5, b.i.d.; day 3 -: 5, q.i.d ± ± ,42 ± ±.61 5, q.i.d ± ± ,821 1,6 ± ±.28 1,, q.i.d. 4 9 ± ± ,4 ± ±.11 5, q.i.d ± , ± ,595 2,41 ± ±.33 1,, q.i.d. 6 2 ± ± ,45 2,12 ± ±.61 Day 1-8: 5, q.i.d.; day 9,1: 5 b.i.d. 7 1,35 ± ,278 1,11 ± ,95 1,35 ± ±.49 Day 1: 5, q.i.d. day 2 -: 1,, q.i.d ± ± ,17 ± ±.24 5, q.i.d. a First dose values not incorporated. Average values given with standard deviations.

4 538 SHERMANTINE ET AL. ANTIMICROB. AGENTS CHEMOTHER. TABLE 3. CLu and unbound fraction values of sulfisoxaole in renal transplant patients CLu (ml/min) CLUR (ml/min) CLUXR (ml/min) CLUACa (ml/min) Fu on day: Subjects on day: on day: on day: on day: Patients b b b 64 24b Mean C 31c 57 6' C ' SD Controlsd Mean SD a Uf,,, unbound fraction. b Patient experienced a rejection episode with rapid deterioration of renal function starting on day 5 of treatment. ' Statistically significantly different from control; P <.5. d There were six controls. In ge-neral, the unbound fraction of sulfisoxaole increased dependent binding of sulfisoxaole. At steady state, the on continued administration of sulfisoxaole. The unbound average molar concentration of sulfisoxaole (324,uM) and fractioin was statistically significantly lower during the first N4-acetyl sulfisoxaole (254,uM) approached the average dosing interval than in the later test periods (P <.2 by the molar concentration of albumin (56,uM) in these patients. Studenit t test). This suggests a time- or concentration- In the normal subjects, the average molar albumin concentration was 65,uM, and saturable protein binding of sulfisoxaole after intravenous dosing was seen only at concentrations of sulfisoxaole in excess of 3,uM (8). 18 Since N4-acetyl sulfisoxaole and sulfisoxaole compete for the same binding site(s) and the combined molar concentrations of these compounds are equal to the molar concentration of albumin in the renal transplant patients, the 16 / decreased binding is probably due to a concentrationo / dependent effect. -j 14 One of the major concerns regarding the use of sulfisoxaole in renal transplant patients is the possibility of o crystalluria, which might compromise the level of renal function in these patients. The exclusion criteria for the use w -j 12 x cn LL 1 -J C,) n 8 U- 6 4 at Li 2 -J wi FIG. nine cllearance. Symbols:, renal transplant patients;, normal sulfisoxaole to N4-acetyl sulfisoxaole will occur, resulting controlis. The relationship is described by CLUR = in a subsequent higher urinary concentration of this metabwhere CLCR is creatinine clearance. olite, which is only one-third as soluble as its parent com- CLCR, of sulfisoxaole in renal transplant patients at the University _/o of California, San Francisco, is either a creatinine concentration in serum of >4 mg/dl or a creatinine clearance of <2 Go /ml/min. A study of patients who conformed to these criteria * showed that no clinical manifestations of crystalluria were observed. However, during the course of this study, we found that three of the eight patients occasionally had concentrations of N4-acetyl sulfisoxaole in urine that theoretically exceeded the solubility of this compound (>1, mg/dl at ph < 6.). However, at that time no change in the * clinical status of the patients was noted. Despite the lack of complications in these patients, we suggest that sulfisoxaole therapy in this patient population be given cau- _ 2 tiously and include a recommendation for adequate fluid _ U 1 I I I I I intake (1 mlih). Care should be taken when treating patients with low urine phs. We also suggest that therapy be CREATININE CLEARANCE, ML/MIN promptly discontinued if renal function deteriorates, be- 3. Correlation between CLUR of sulfisoxaole and creati- cause an increase in the fractional conversion of Downloaded from on July 22, 218 by guest

5 VOL. 28, 1985 pound (13). Additionally, excess N4-acetyl sulfisoxaole appears more difficult than sulfisoxaole to remove by dialysis. In one renal transplant patient (not included in this study) who underwent hemodialysis, the extraction ratio of N4-acetyl sulfisoxaole was.66 ±.7. The extraction ratio for sulfisoxaole, however, was In all patients the unbound concentrations in plasma, as well as those in urine, were at all times after the first dose at levels considered to be active against sulfisoxaole-susceptible microorganisms. The total recovery of sulfisoxaole and N4-acetyl sulfisoxaole over the total study period was 63.5 ± 7.4%, compared with a recovery in normal controls of 8% (9). With the use of the Bratton-Marshall method for total sulfisoxaole (5), 92% of the dose could be accounted for after hydrolysis, which is lower than that observed in healthy controls (19%). Part of the lower total recovery is probably related to the difficulty in assuring complete urine collection over the 12- to 21-day study period for the individual patients. During the steady state, when three or more 2-h urine samples were collected, the recovery by the Bratton-Marshall method was 99%. Similarly, the sulfisoxaole and N4-acetyl sulfisoxaole recovery was 36 and 38%, respectively, versus 32% each for the total study period. It therefore appears to be unlikely that total recovery of sulfisoxaole from urine was achieved consistently throughout the study. The total recovery of sulfisoxaole was, on the other hand, only correlated with the daily urine flow in one of the eight patients (P <.5 by the Student t test). A correlation was only expected if a large amount of urine was lost on occasions; this indicates that the urine volume lost due to inadequate collection is small. The clearance determination samples were, on the other hand, collected under more controlled conditions and are likely to better represent the ability to eliminate sulfisoxaole. The excretion of sulfisoxaole from urine did not consistently vary with urine ph, urine flow rate, or creatinine levels in serum in individual subjects. Several reasons may account for this phenomenon. The urine ph, urine flow rate, and creatinine levels in serum tended to vary relatively little throughout the study in the individual patients. Only when large changes were seen in urine ph, urine flow rate, and creatinine levels in serum could a correlation be found. In all subjects (transplant patients and controls), the majority of the variability in the CLUR of sulfisoxaole could be explained by the difference in creatinine clearance values (Fig. 3). It is, however, interesting to note that the linear relationship between CLUR and creatinine clearance has a negative intercept on the y axis. Because the four subjects with the lowest CLus were among the subjects with the lowest urine ph, the deviation from a straight line through the origin may be due to higher-than-average reabsorption in these subjects. However, the r2 value for the multiple correlation between CLUR and creatinine clearance, urine flow rate, and urine ph (.8823) was not marginally different from the r2 value for the correlation between CLUR and creatinine clearance alone (.8597). SULFIZOXAZOLE IN TRANSPLANT PATIENTS 539 In summary, the kinetics of unbound sulfisoxaole in renal transplant patients was predictable from data in normal volunteers after adjusting for differences in renal function. Differences in the kinetics of total sulfisoxaole were, on the other hand, quite notable, mainly owing to a lower binding to protein in plasma in the renal transplant patients. The lowered binding could be related to a lower albumin concentration and an accumulation of N4-acetyl sulfisoxaole, a displacer of sulfisoxaole. ACKNOWLEDGMENTS This study was supported in part by Public Health Service grants GM and GM 2587 from the National Institutes of Health. LITERATURE CITED 1. Appel, G. B., and H. C. New The nephrotoxicity of antimicrobial agents. N. Engl. J. Med. 296: Ascher, N. L., R. L. Simmons, S. Macher, and J. S. Naarian Listeria infection in transplant patients. Arch. Surg. 113: Avram, M. M., S. R. Nair, H. I. Lipner, and C. E. Cherubin Persistent nocardemia following renal transplantation. J. Am. Med. Assoc. 239: Bekersky, I., and W. A. Colburn Acetylation of sulfisoxaole by isolated perfused rat kidney. J. Pharm. Sci. 69: Bratton, A. C., and E. K. Marshall, Jr A new coupling component for sulfanilamide determination. J. Biol. Chem. 128: Cohen, M. L., E. B. Weiss, and A. P. Monaco Successful treatment of Pneumocystis carinii and Nocardia asteroides in a renal transplant patient. Am. J. Med. 5: Jung, D., and S. ie "High pressure" liquid chromatography of sulfisoxaole and N4-acetylsulfisoxaole in body fluids: Clin. Chem. (NY) 26: Jung, D., and S. ie Decreased in vivo acetylation of sulfisoxaole in the rabbit in the presence of 4-N-acetylsulfisoxaole. Int. J. Pharm. 7: ie, S Effect of 4N-acetyl-sulfisoxaole on the disposition of sulfisoxaole in the rat. Int. J. Pharm. 3: a.ie, S Pharmacokinetics of sulfisoxaole in rabbits with experimental renal failure after single and multiple dosing. Int. J. Pharm. 23: ie, S., J. G. Gambertoglio, and L. Fleckenstein Comparison of the disposition of total and unbound sulfisoxaole after single and multiple dosing. J. Pharmacokinet. Biopharm. 1: Reidenberg, M. M., H. Kostenbauder, and W. P. Adams Rate of drug metabolism in obese volunteers before and after starvation and in aotemic patients. Metabolism 18: Rieder, J Quantitative determination of the bacteriostatically active fraction of sulfonamides and the sum of their inactive nietabolites in the body fluids. Chemotherapy 17: Windhol, M. (ed.) The Merck index, p Merck & Co., Inc., Rahway, N.J. 14. Yacobi, A., and G. Levy Intraindividual relationships between serum protein binding of drugs in normal human subjects, patients with impaired renal function, and rats. J. Pharm. Sci. 66: Downloaded from on July 22, 218 by guest