Comparative clinical pharmacology of intravenous cefoxitin and cephalothin

Pharmacokinetics of intravenously administered cefmetazole and cefoxitin and effects of probenecid on cefmetazole elimination

Sixteen healthy male volunteers participated in a randomized, balanced, three-way crossover study comparing the pharmacokinetics of cefmetazole, cefoxitin, and cefmetazole with probenecid pretreatment. Single 2-g doses of cefmetazole sodium and cefoxitin sodium were given intravenously as a 5-min infusion. Concentrations of cefmetazole and cefoxitin were determined by using a specific semiautomated high-performance liquid chromatographic method. Concentration-time profiles of cefmetazole and cefoxitin declined in a biexponential manner from peak levels. Compared with cefoxitin, cefmetazole had a significantly (P less than 0.05) higher mean (+/- standard error of the mean) peak concentration in serum (290 +/- 11 versus 244 +/- 10 micrograms/ml), a longer terminal disposition half-life (1.50 +/- 0.14 versus 0.81 +/- 0.04 h), lower systemic clearance (111.7 +/- 4.7 versus 279 +/- 12 ml/min) and renal clearance (78.7 +/- 4.3 versus 221 +/- 14 ml/min) of intact drug, and a slightly smaller steady-state volume of distribution (10.3 +/- 0.21 versus 12.8 +/- 0.48 liters). Mean recoveries of cefmetazole and cefoxitin in urine were approximately 71 and 77%, respectively. Pretreatment of volunteers with probenecid (1 g orally) significantly (P less than 0.05) increased concentrations of cefmetazole in serum 1 h after drug administration without significantly increasing maximum concentrations in serum. Mean areas under the concentration-time curve (466 +/- 27 versus 295 +/- 13 micrograms.h/ml) and terminal disposition half-lives (2.27 +/- 0.13 versus 1.50 +/- 0.14 h) of cefmetazole increased. Systemic clearance (72.1 +/- 4.0 versus 111.7 +/- 4.7 ml/min) and renal clearance (47.4 +/- 4.0 versus 78.7 +/- 4.3 ml/min) of intact antibiotic decreased. Mean recoveries (65.9 +/- 3.7 versus 71.0 +/- 3.2%) of intact cefmetazole in urine were not significantly (P > 0.05) different. Elimination of cefmetazole in urine was also significantly prolonged by probenecid, with substantial concentrations of cefmetazole (>/= 20 micrograms/ml) found in the 12- to 24-h urine collection for 14 to 16 volunteers. The results show that cefmetazole remains at clinically relevant concentrations (1 to 2 micrograms/ml) approximately twice as long as cefoxitin, that serum cefmetazole can be maintained longer at clinically significant concentrations with preadministration of probenecid, and that cefmetazole is partially eliminated by renal tubule secretion.

Use of adjuvants for enhancement of rectal absorption of cefoxitin in humans

The biological availability of cefoxitin administered rectally in the form of suppositories was examined in six human subjects by a cross-over design. Four different suppository systems containing adjuvants expected to enhance the absorption of the drug were studied. The presence of sodium salicylate and a nonionic surface-active agent, Brij 35, gave increased bioavailability as high as 20% compared with 3% for a system without adjuvants. The quantity of sodium salicylate was found to have an influence on the quantity of cefoxitin absorbed, and the salicylate was absorbed over an extended period of time from the rectum. The suppositories were well tolerated, and there were no adverse effects on bowel flora.

Comparative pharmacokinetics of cefoxitin in postpartum normotensive and pregnancy-induced hypertensive patients

Limited pharmacokinetic data exist on cefoxitin, a semisynthetic cephamycin antibiotic, in the obstetric patient. Thirteen normotensive and five subjects with severe pregnancy-induced hypertension were identified within the first two postpartum days after cesarean section. After a 2 gm intravenous infusion, serial samples of blood were obtained and analyzed for cefoxitin by high-pressure liquid chromatography. Peak cefoxitin concentrations after infusion were 53.3 +/- 18.6 and 50.8 +/- 25.2 micrograms/ml for the normotensive and pregnancy-induced hypertensive groups, respectively. The only significant difference in pharmacokinetic parameters between these groups was a higher serum trough concentration of cefoxitin in the patients with pregnancy-induced hypertension as compared to the normotensive group. Because of diminished trough levels in our study patients, attention may need to be given to the adjustment of dosages in postpartum women with serious infections.

Methods in testing interrelationships between excretion of drugs via urine and bile

The liver and kidney are largely responsible for inactivating and eliminating drugs and other chemicals. As the excretory capabilities of the two organs overlap, a damage of one system might be compensated by the other. Because of the specificity of both renal and hepatic elimination mechanisms such an alternative excretion route is not possible generally. Several interferences are possible to characterize the relation between hepatic and renal excretion of drugs and xenobiotics. Firstly, the simultaneous assay of excreted drug amounts in urine and bile can give some information concerning the main transport routes of this drug. Thereafter the total interruption of liver or kidney function elucidates the general possibility of alternative excretion routes. But it is important for clinical practice to distinguish between different localizations of organ damages. Today some experimental possibilities exist to exclude partial functions of both kidney and liver separately. Thus it can be clarified why a compound might be excreted via liver or kidney. Moreover it can be characterized whether or not a compensation for the loss of one main excretion organ is possible or not. Such investigations are of some practical importance. Dosing guidelines for drug therapy must be completed for cases of renal or hepatic failure. Moreover the developmental pattern of both elimination routes has consequences for drug use in paediatrics as well as geriatrics. Beside this point of view such investigations are necessary for the prediction of changes in the toxicity of drugs after renal or hepatic insufficiency.

Cefotaxime. A review of its antibacterial activity, pharmacological properties and therapeutic use

SYNOPSIS

Cefotaxime is a new 'third generation' semisynthetic cephalosporin administered intravenously or intramuscularly. It has a broad spectrum of activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria, and is generally more active against Gram-negative bacteria than the 'first' and 'second generation' cephalosporins. Although cefotaxime has some activity against Pseudomonas aeruginosa, on the basis of present evidence it cannot be recommended as sole antibiotic therapy for pseudomonal infections. However, cefotaxime has been effective in treating infections due to other 'difficult' organisms, such as multidrug-resistant Enterobacteriaceae. Like other cephalosporins, cefotaxime is effective in treating patients with complicated urinary tract and lower respiratory tract infections, particularly pneumonia caused by Gram-negative bacilli. High response rates have also been achieved in patients with Gram-negative bacteraemia. Although favourable clinical results have been obtained in patients with infections caused by mixed aerobic/anaerobic organisms (such as peritonitis or soft tissue infections), the relatively low in vitro activity of cefotaxime against Bacteroides fragilis may restrict its usage in situations where this organism is the suspected or proven pathogen. In preliminary studies, males and females treated with a single intramuscular dose of cefotaxime for uncomplicated gonorrhoea caused by penicillinase-producing strains of Neisseria gonorrhoeae responded very favourably. Encouraging results have also been reported in open studies in children including neonates, treated with cefotaxime for meningitis and various other serious infections. In some situations, cefotaxime has been given in combination with another antibiotic such as an aminoglycoside, but the merits of such a combination have not been clearly established. Whether cefotaxime alone is appropriate therapy for conditions previously treated with aminoglycosides (other than pseudomonal infections) also needs additional clarification, but if established as equally effective in such conditions cefotaxime offers potentially important clinical and practical advantages in its apparent lack of serious adverse effects and freedom from the need to undertake drug plasma concentration monitoring.

Antibiotic prophylaxis in gynecology: cefoxitin concentrations in serum, myometrium, endometrium and salpinges

Thirty-six patients received an intravenous bolus injection of 2 g cefoxitin over 5 min at various times before abdominal or vaginal hysterectomy. Cefoxitin levels in myometrium and salpinges were substantially higher than those in endometrium and almost as high as those in serum during the first two hours following the i. v. administration of the drug. Tissue concentrations of 8 micrograms/g could be maintained for two hours. The cefoxitin tissue concentrations attained in myometrium, endometrium and salpinges justify controlled prospective clinical studies on the prevention of postoperative wound infections with this antibiotic.

Disposition of cefoxitin in patients with ascites

The pharmacokinetics of Cefoxitin was studied in 8 cirrhotic patients with ascites after i.v. administration of a single 30 mg/kg dose. Concentrations of cefoxitin in serum and in ascitic fluid were determined simultaneously and by a microbiologic plate diffusion method. The antibiotic followed a two-compartment open kinetic model. In ascitic fluid, Cefoxitin reached its maximum concentration of 32.80 +/- 13,78 micrograms/ml 2 h after administration. The mean elimination constant from ascitic fluid was 0.201 +/- 0.008 h(-1), significantly lower (p less than 0.05) than the slow disposition phase constant (beta = 0.556 +/- 0.17 h(-1)). At the dose studied and with a dosage interval of 8 h, the level of antibiotic in the ascitic fluid would be maintained at a value greater than the MIC of most cefoxitin-sensitive organisms.

Pharmacokinetics of cefmetazole in normal subjects and in patients with impaired renal function

The pharmacokinetics of cefmetazole, a new cephamycin antibiotic, were examined after a 1-h intravenous drip infusion of 1 g to 5 healthy volunteers with normal renal function and 16 patients with impaired renal function. Peak serum concentrations were obtained at the end of the infusion in all subjects, regardless of their renal function. Approximately 70% of the infused dose was excreted in the urine within 6 h in healthy volunteers. The pharmacokinetic parameters of cefmetazole were derived by analyzing elimination data, with a one-compartment open model. The mean serum half-life of cefmetazole in healthy volunteers was 0.81 h. A significant correlation between the elimination rate constant and the creatinine clearance was demonstrated.

Effect of lidocaine on the absorption, disposition and tolerance of intramuscularly administered cefoxitin

The use of lidocaine HCL solution at concentrations of 0.5 and 1.0% to reconstitute sodium cefoxitin relieves the pain associated with intramuscular injections of the antibiotic. Cefoxitin absorption by the intramuscular route is initially rapid and is virtually complete. Peak serum concentrations, corresponding to about one-half those of a comparable intravenous infusion, are achieved in 30 min. Continuing absorption tends to maintain higher serum concentrations for longer times. Renal clearance and serum half-life of cefoxitin do not appear to be affected by lidocaine at its effective anaesthetic concentrations.