Effects of rate of infusion and probenecid on serum levels, renal excretion, and tolerance of intravenous doses of cefoxitin in humans: comparison with cephalothin

β-Lactam antibiotics targeting PBP1 selectively enhance daptomycin activity against methicillin-resistant Staphylococcus aureus

The activity of daptomycin (DAP) against methicillin-resistant Staphylococcus aureus (MRSA) is enhanced in the presence of subinhibitory concentrations of antistaphylococcal β-lactam antibiotics by an undefined mechanism. Given the variability in the penicillin-binding protein (PBP)-binding profiles of different β-lactam antibiotics, the purpose of this study was to examine the relative enhancement of DAP activity against MRSA by different β-lactam antibiotics to determine if a specific PBP-binding profile is associated with the ability to enhance the anti-MRSA activity of DAP. We determined that both broad- and narrow-spectrum β-lactam antibiotics known to exhibit PBP1 binding demonstrated potent enhancement of DAP anti-MRSA activity, whereas β-lactam antibiotics with minimal PBP1 binding (cefoxitin, ceftriaxone, cefaclor, and cefotaxime) were less effective. We suspect that PBP1 disruption by β-lactam antibiotics affects pathways of cell division in S. aureus that may be a compensatory response to DAP membrane insertion, resulting in DAP hypersusceptibility.

Novel quinolinone-phosphonic acid AMPA antagonists devoid of nephrotoxicity

We reported previously the synthesis and structure-activity relationships (SAR) in a series of 2-(1H)-oxoquinolines bearing different acidic functions in the 3-position. Exploiting these SAR, we were able to identify 6,7-dichloro-2-(1H)-oxoquinoline-3-phosphonic acid compound 3 (S 17625) as a potent, in vivo active AMPA antagonist. Unfortunately, during the course of the development, nephrotoxicity was manifest at therapeutically effective doses. Considering that some similitude exists between S 17625 and probenecid, a compound known to protect against the nephrotoxicity and/or slow the clearance of different drugs, we decided to synthesise some new analogues of S 17625 incorporating some of the salient features of probenecid. Replacement of the chlorine in position 6 by a sulfonylamine led to very potent AMPA antagonists endowed with good in vivo activity and lacking nephrotoxicity potential. Amongst the compounds evaluated, derivatives 7a and 7s appear to be the most promising and are currently evaluated in therapeutically relevant stroke models.

Cephalosporin-probenecid drug interactions

The effect of concurrent probenecid administration on the pharmacokinetics of cephalosporin antibiotics varies with the available cephalosporins. Most cephalosporins are affected to some degree by concurrent probenecid administration, although ceforanide, ceftazidime, ceftriaxone and latamoxef (moxalactam) have no significant changes in pharmacokinetics. For those cephalosporins affected by probenecid, the predominant findings are impairment in renal clearance resulting in increased peak serum concentrations, an increased area under the concentration-time curve (AUC), and both delayed and prolonged recovery of the cephalosporin in the urine. The distribution of the cephalosporins is affected to varying degrees, with reports of increased penetration into ocular, central nervous system and blister fluids noted with some agents. The clinical relevance of the changes in cephalosporin distribution associated with probenecid administration has not been investigated. The dose and timing of probenecid administration appear to be major determinants in any possible interaction. Studies with ceftizoxime and cefoxitin suggest that larger probenecid doses result in greater changes in the pharmacokinetics of cephalosporins. Prolonged probenecid therapy before administration of a cephalosporin did not seem to be as relevant as the probenecid dosage in determining the magnitude of the interaction. Probenecid administration with or immediately before cephalosporin administration appears able to produce these documented changes in cephalosporin pharmacokinetics. The route of administration (oral versus parenteral) of either prolosporin pharmacokinetics. The route of administration (oral versus parenteral) of either probenecid or the cephalosporin does not appear to influence the characteristics of the interactions. The therapeutic efficacy of a combination of a cephalosporin with probenecid has been most thoroughly studied for single-dose treatment of gonorrhoea. The addition of probenecid to cephalosporin therapy results in sustained systemic concentrations adequate for eradication of Neisseria gonorrhoeae. Regimens involving either second or third generation cephalosporins demonstrate good success rates with single-dose therapy. However, the success of ceftriaxone administered alone for treatment of both penicillase-producing and non-penicillase-producing strains of N. gonorrhoeae suggests that the addition of probenecid is unnecessary. The use of probenecid, in combination with cephalosporins, to enhance the treatment of other venereal and systemic infections has preliminary, inconclusive support.

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.

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.

The Wagner-Nelson method applied to a multicompartment model with zero order input

It is shown that the Wagner-Nelson absorption method provides zero-order input rate constants exactly, or with small error, in a large number of cases where the two-compartment open disposition model applies. Factors affecting the accuracy of the method were studied with error-free simulated data. The method was applied to real data for three drugs. With ethanol infused over 2 h in eight human trials the estimated rate constant averaged 99.6 per cent of the known rate constant with a coefficient of variation of 6.86 per cent. With pindolol infused over 3 h five human subjects the estimated rate constant averaged 98.7 per cent of the known rate constant with a coefficient of variation of 22.5 per cent. With theophylline administered orally in a sustained-release form to seven human subjects the Wagner-Nelson method provided estimated zero-order rate constants which averaged 95.8 per cent of those estimated by an exact two-compartment absorption equation with a coefficient of variation of 38.1 per cent (in this case bolus intravenous data were available for the same subjects).

Significance of ratios of different volumes of distribution in pharmacokinetics

Multicompartmental pharmacokinetics involves the four volumes: Vc = volume of the central compartment; Vss = volume of distribution steady-state; V beta = volume of distribution beta; and Vext = the extrapolated volume of distribution. The ratio Vc/Vext is indicative of the degree of multicompartmental character of a set of data. The quantity (Vext/V beta)--1 is the fractional error in the total clearance when one assumes a monoexponential rather than a polyexponential equation for disposition of a drug. The ratio Vss/V beta indicates how well the one-compartment body model predicts average amounts of drug in the body when a multicompartmental model is actually operative. The quantity (Vss/Vc)--1 is equal to either k12/k21 or k12/k21 + k13/k31 of the two- and three-compartmental mammillary models. Examples from the literature are reported and discussed.

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.

Cefoxitin therapy in aerobic, anaerobic, and mixed aerobic-anaerobic infections

Cefoxitin, a new beta-lactamase-resistant cephamycin, was evaluated in 66 patients for clinical and bacteriological efficacy, serum levels, tolerance, and toxicity. Seventeen patients had soft tissue infections, 14 had pleuropulmonary infections, 14 had intraabdominal infections, 13 had pelvic infections, and 8 had urinary tract infections. Among the 66 patients, 62 were cured and 4 could not be evaluated. Twelve patients had hospital-acquired infections, 31 had underlying disease, and 45 required a surgical procedure. Isolates included 116 aerobic and 72 anaerobic bacteria. Cefoxitin was more active than cephalothin against facultative and obligate anaerobic gram-negative organisms isolated from these patients. Mean peak cefoxitin levels in sera were 52 micrograms/ml after a 2-g infusion and 30 micrograms/ml after a 1-g infusion. Phlebitis occurred in two patients, eosinophilia in one, rash in two, vasculitis in one, and transient rises in SGOT and SGPT in two. Cefoxitin appears to be a safe and effective drug for the treatment of many aerobic, anaerobic, and mixed aerobic-anaerobic infections.

The effect of probenecid on the pharmacokinetics and distribution of cefoxitin in healthy volunteers

1 Cefoxitin was given by acute intravenous injection to six healthy volunteers, in a crossover study to investigate the effects of concurrent probenecid administration. 2 Serum antibiotic concentrations were determined by microbiological assay. Cefoxitin concentrations were simultaneously determined in the fluid of blisters produced by topical cantharides. All antibiotic was accounted for in the urine. 3 Cefoxitin was administered by intravenous infusion, subsequent to a loading dose, to produce steady state levels in the region of 10 microgram/ml, in one volunteer. The procedure was later repeated after prior administration of probenecid in the same subject. 4 Pharmacokinetic analyses indicated significant changes only in the parameters associated with renal excretion of drugs. Clearance was reduced by half. 5 The absolute and relative amounts of antibiotic in the central and peripheral compartments were calculated for both modes of administration. In the acute study probenecid produced a small change in distribution away from the peripheral or tissue compartment, towards the central compartment. 6 There was no elevation of initial serum concentrations and sustained levels of antibiotic could be accounted for principally by retarded excretion produced by probenecid, with little contribution by alteration in the disposition of antibiotic. 7 The sustained serum levels of cefoxitin that resulted from its decreased excretion were also reflected in blister fluid. It was concluded that the sustained cefoxitin levels produced by probenecid resulted in similar raised levels in the peripheral or "tissue' compartment, since the redistribution away from the peripheral compartment did not contribute materially to other changes in disposition of drug.

Clinical pharmacokinetics of probenecid

A review of the clinical applications and of the disposition of probenecid in man, including drug interactions, is presented. Probenecid is the classical competitive inhibitor of organic acid transport in the kidney and other organs. There are 2 primary clinical uses for probenecid: as a uricosuric agent in the treatment of chronic gout and as an adjunct to enhance blood levels of antibiotics (such as penicillins and cephalosporins). Adsorption of probenecid is essentially complete following oral administration. The drug is extensively metabolised by glucuronide conjugation and by oxidation of the alkyl side chains; oxidation of the aromatic ring does not occur. The half-life of probenecid in plasma (4 to 12 hours) is dose-dependent. Renal excretion is the major route of elimination of the metabolites; excretion of the parent drug is minimal and is dependent on urinary pH. Probenecid and its oxidised metabolites are extensively bound to plasma proteins, mainly to albumin. Tissue concentrations (based on animal studies) are generally lower than plasma concentrations. Most of the drug-drug interactions involving probenecid are due to an effect on the kidney-block of transport of acidic drugs. Similarly probenecid affects the tubular secretion of a number of acidic endogenous substances by the kidney. Probenecid is also involved in the block of transport of acidic metabolites of catecholamines, for example homovanillic and hydroxyindoleacetic acids, in the brain. There are a number of analytical procedures for the assay of probenecid. These are based on spectrophotometry, spectrofluorometry, gas and liquid chromatography and radioimmunoassay.

New in vitro kinetic model for evaluating bactericidal efficacy of antibiotics

A new in vitro model was devised for evaluating the bactericidal activity of antibiotics under dynamic conditions. This model accurately reproduced the observed serum levels of antibiotics after intravenous dosing. The apparatus consists of two vessels which correspond to the central and peripheral compartments of a two-compartment open model. The volume of medium in each vessel and flow rates of media were determined from the pharmacokinetic parameters calculated from the observed serum levels selected for simulation. The bactericidal activity of cefazolin against strains of Escherichia coli and Klebsiella pneumoniae showing different minimal inhibitory concentrations was investigated with the apparatus simulating serum levels after intravenous injection, and the bactericidal activity was evaluated with respect to the relationship between the minimal inhibitory concentration and the serum levels.

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 orally administered probenecid on the pharmacokinetics of cefoxitin

To characterize the effect of orally administered probenecid on the pharmacokinetics of cefoxitin in healthy male volunteers, we administered to one group of six subjects 2 g of cefoxitin by intravenous (i.v.) bolus either alone, with 1 g of probenecid concomitantly, or when 1 g of probenecid was administered 1 h previously by using a crossover design. Likewise, we administered to a second group of six subjects 2 g of cefoxitin intramuscularly (i.m.) together with 1 and 2 g of probenecid. Probenecid increased the mean terminal half-life and the area under the serum cefoxitin concentration-time curve (AUC0-24) and decreased renal clearance, but did not alter the volume of the central compartment or the total urinary recovery of i.v.-administered cefoxitin; pretreatment with probenecid produced a greater increase in cefoxitin AUC0-24 and a constant decrease in renal clearance compared to concomitant probenecid. The AUC0-24 after i.m.-administered cefoxitin was greater after 2 g than 1 g of probenecid; the AUC0-24 after i.v.-and i.m.-administered cefoxitin was similar after 1 g of probenecid was given concomitantly. Cefoxitin AUC0-24 was increased further when 1 g of probenecid was given before i.v.-administered cefoxitin or when 2 g of probenecid was given with i.m.-administered cefoxitin. The effect of probenecid was related to both timing and dose.

Clinical and pharmacokinetic evaluation of parental cefoxitin in infants and children

Thirty-two infants and children ranging in age from 3 to 151 months (mean, 26 months) were treated with parenteral cefoxitin (150 mg/kg per day). Ten patients with isolates of Haemophilus influenzae (six with cellulitis, two with arthritis, and two with mastoiditis), four with Staphylococcus aureus (one with lymphadenitis, one with septicemia, and two with abscess), and three patients with Streptococcus pneumoniae (one each with cellulitis, abscess, and arthritis), were clinically and bacteriologically cured by therapy. Two additional patients with septic arthritis and facial cellulitis developed meningitis with H. influenzae type b and S. pneumoniae, respectively. Minimal inhibitory and bactericidal concentrations were </=5 mug/ml for 15 isolates. Minimal bactericidal concentrations were >20 mug/ml for one strain of S. aureus and one of H. influenzae type b. The mean peak serum levels were 81.9 and 68.5 mug/ml 15 min after intravenous or intramuscular doses, respectively. The mean elimination half-lives were 42.4 and 40.1 min after intravenous or intramuscular doses, respectively. The mean volumes of distribution were 5,540 and 4,760 ml after intravenous and intramuscular doses, respectively. Mean plasma clearance was 242 and 257 ml/min per m(2) after intravenous and intramuscular doses, respectively. Therapy was discontinued in one patient because of neutropenia, which resolved after cefoxitin was stopped. Eosinophilia and transiently elevated liver function tests occurred in eight and six patients, respectively. These data indicate that cefoxitin may be an effective treatment for infections due to susceptible bacteria in the dosage tested, but its use may be limited because of the occurrence of meningitis during therapy in some patients.

Cefoxitin: a review of its antibacterial activity, pharmacological properties and therapeutic use

Cefoxitin is a beta-lactam antibiotic derived from cephamycin C, a naturally occurring substance produced by Streptomyces lactamdurans. Its resistance to destruction by beta-lactamases results in a broad spectrum of antibacterial activity which includes anaerobic as well as Gram-positive and Gram-negative aerobic bacteria, including many resistant to cephalothin and other cephalosporins. Given by intravenous or intramuscular injection, cefoxitin is effective against a wide variety of infections caused by Gram-positive or Gram-negative aerobes as well as by anaerobic bacteria. It is generally well tolerated, thrombophlebitis, skin rash and some degree of discomfort after intramuscular injection, being the most commonly reported side effects. Cefoxitin has not been shown to cause adverse effects on renal function.

Use of cefoxitin, new cephalosporin-like antibiotic, in the treatment of aerobic and anaerobic infections

Forty-two patients were treated with intravenous cefoxitin, a new cephamycin antibiotic. These patients had postoperative abdominal sepsis (26), intrathoracic infections (6), urinary tract infections (5), gram-negative bacterial meningitis (2), septic arthritis (1), epidural abscess (1) and isolated septicemia (1). The antibacterial spectrum of cefoxitin was found to be one which included all gram-positive organisms except enterococci, most gram-negative organisms except Pseudomonas aeruginosa, and almost all of the important anaerobic organisms. The only five treatment failures included one patient with empyema and one with septic arthritis, both caused by Serratia marcescens, initially only moderately susceptible to cefoxitin, which subsequently developed increased resistance, two patients with contaminated intravenous catheters, and one patient with epidural abscess and cerebritis, who was treated late in the course. There was one serious clinical superinfection with P. aeruginosa. The drug levels noted in the pus and joint fluid were half to two-thirds of the simultaneous serum level. In inflamed meninges, up to 30% of the serum level was noted in the cerebrospinal fluid, and as the process resolved, 10 to 15% was noted. Toxicity of cefoxitin was mild and constituted skin rash in three patients (7%) and phlebitis in eight (19%).

Studies of intravenous cefoxitin (MK306)

The pharmacokinetics of cefoxitin, a new cephamycin antibiotic, were studied in six patients who were undergoing total hip replacement, and who were given cefoxitin to provide prophylactic cover at the time of operation. Later, the efficacy of cefoxitin was studied in nine patients with severe acute infections. The mean elimination phase half-life of cefoxitin which was obtained in this study (83 to 87 minutes) was significantly longer than that obtained in other studies. Cefoxitin was also found to be effective in lung and urinary tract infections against sensitive organisms. It was well tolerated, and the only side effect was that of phlebitis in long-term therapy. Cefoxitin may be valuable for prophylactic use in bowel and orthopaedic surgery.

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.

The pharmacokinetics of cefuroxime after intravenous injection

Cefuroxime, a new cephalosporin antibiotic which is stable to most beta-lactamases produced by gram-negative bacteria, was given by bolus intravenous injection to six volunteers in doses of 500 mg and 750 mg. The concentrations of cefuroxime in serum and urine were measured at pre-determined times after injection and the data analysed by a two-compartment open system model. A serum concentration of 8 microgram/ml was exceeded for 100.3 min (+/- 18.3) after a 500 mg dose and for 144.5 min (+/- 19.8) after 750 mg. The ultimate serum half-life was 1.1 h. Excretion of cefuroxime in the urine was almost complete in 24 h, the clearance being 150 ml/min/1.73m2. About 45% was excreted through the renal tubules. The injections were well tolerated and no changes in haematological or biochemical values were seen. The resulting data are compared with those published for some other cephalosporins. It is concluded that the favourable pharmacokinetics, especially the high concentrations of unbound cefuroxime in the serum, are likely to aid effective therapy of human infection caused by sensitive bacteria.

Cefoxitin: clinical evaluation in thirty-eight patients

Clinical and bacteriological efficacy, patient tolerance, and toxicity of cefoxitin, a beta-lactamase-resistant cephamycin, were evaluated in 38 patients; 13 had soft tissue infection, 12 had pneumonia, 3 had urinary tract infection, 2 had peritonitis, and 4 had miscellaneous infections. In five patients, infection was clinically evident, though not bacteriologically proven. The latter patients were evaluated with regard to tolerance and toxicity only. Among the 34 infections in 33 patients, 71% were considered clinically cured; 86% of those patients who could be recultured were bacteriologically cured. Phlebitis was noted in 32% of the total group, and eosinophilia was observed in 16%. Unexplained deterioration in renal function occurred in two patients. Mean peak cefoxitin levels in serum were 72 mug/ml 30 min after a 2-g infusion and 32 mug/ml 30 min after a 1-g infusion. Cefoxitin was more active against facultatively and obligately anaerobic gram-negative organisms isolated from these patients than was cephalothin.

Lysis if enterobacteria by cefoxitin, cefuroxime, and cephalothin

Cefoxitin, cefuroxime, and cephalothin were added to dense populations of beta-lactamase-producing enterobacteria, and the subsequent turbidity changes were monitored continuously. Viable counts and antibiotic assays were made at intervals after the addition of antibiotic, and the morphological appearances of the organisms were observed. Cephalothin caused lysis of most of the organisms tested, but even at high concentrations, after a few hours the antibiotic was destroyed and the organisms recommenced logarithmic growth. Cefoxitin produced lysis of all the strains of Escherichia coli and Klebsiella species tested, with supression of regrowth. With cephalothin and cefoxitin the viable counts after the addition of antibiotic correlated with the turbidity measurements. Cefuroxime infrequently caused lysis that suppressed multiplication, and the organisms became long and filamentous while the turbidity readings increased; the viable counts did not correlate with the turbidity measurements. Cefuroxime and cefoxitin were not destroyed by the beta-lactamases of any of the strains of enterobacteria that were studied.

Cefoxitin activity against multiply antibiotic-resistance Klebsiella pneumoniae in vitro

Due to the emergence of cephalothin- and gentamicin-resistant Klebsiella pneumoniae at this institution, we investigated the in vitro activity of two new cephalosporin compounds-cefoxitin and cefamandole. Whereas both drugs were active against cephalothin- and gentamicin-susceptible isolates of Klebsiella, only cefoxitin exhibited significant activity against cephalothin- and gentamicin-resistant isolates. Seventeen of 20 (85%) of the cephalothin- and gentamicin-resistant isolates were inhibited by </=12.5 mug of cefoxitin per ml. The minimum bactericidal concentration in broth of representative isolates equaled the agar dilution minimum inhibitory concentration. Kirby-Bauer disk susceptibility testing correlated well with the agar dilution minimum inhibitory concentration. Cephalothin and cefamandole resistance of isolates could be correlated with antibiotic degradation by beta-lactamase. Cephalothin and cefamandole evoked only a transient decrease in viable bacterial cell count with rapid inactivation of antibiotics, and full regrowth of the organisms. Cefoxitin, on the other hand, was quite effective in vitro against multiply resistant Klebsiella. No beta-lactamase degradation of cefoxitin was detected. Growth curves with antibiotics indicated rapid killing of cephalothin- and gentamicin-resistant isolates by cefoxitin.

Cephamycins: a review, prospects and some original observations

The cephamycins are a group with great potential. The first member of the group intended for therapeutic use offers the following advantages over existing cephalosporins: 1. Stability to various beta-lactamases; in an environment increasingly threatened by R-factors, this property may be of increasing value as time passes. 2. Possible lack of cross-allergenicity with other beta-lactam antibiotics. 3. Activity against anaerobic strains. Cefoxitin is only the first semi-synthetic derivative; presumably there are other compounds awaiting assessment which have even more favourable properties.