The in vitro activity of N-formimidoyl thienamycin compared with other broad-spectrum cephalosporins and with clindamycin and metronidazole

Bile levels of imipenem in patients with T-drain following the administration of imipenem/cilastatin

Twenty-four patients undergoing gall bladder surgery and placement of a Kehr T-tube were examined for imipenem pharmacokinetics in plasma and bile fluid following an intravenous short-term infusion (20 min) of 500 mg respectively 1000 mg each of imipenem and cilastatin. In group I (500 mg; 12 patients) a mean peak concentration in bile fluid of 10.5 mg/l (range 1.5 to 16.7 mg/l) was reached just after 10 min. 60 min after the end of infusion the imipenem concentration was between 8 and 9 mg/l. In group I the half-life of imipenem in bile was 0.84 h. In group II (1000 mg; 12 patients) the mean peak level in bile fluid was 1&.5 mg/l (range 3.5 to 51.3 mg/l). The half-life in bile was 1.24 h in this group. The data indicated that 4 h after the administration of either 1000 mg or 500 mg, imipenem serum and bile concentrations were markedly above the MIC values for pathogens expected to be found in infections of the biliary tract.

Imipenem/cilastatin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic efficacy

Imipenem is the first available semisynthetic thienamycin and is administered intravenously in combination with cilastatin, a renal dipeptidase inhibitor that increases urinary excretion of active drug. In vitro studies have demonstrated that imipenem has an extremely wide spectrum of antibacterial activity against Gram-negative and Gram-positive aerobic and anaerobic bacteria, even against many multiresistant strains of bacteria. It is very potent against species which elaborate beta-lactamases. Imipenem in combination with equal doses of cilastatin has been shown to be generally well tolerated and an effective antimicrobial for the treatment of infections of various body systems. It is likely to be most valuable as empirical treatment of mixed aerobic and anaerobic infections, bacteraemia in non-neutropenic patients and serious hospital-acquired infections.

Impact of imipenem/cilastatin therapy on normal fecal flora

The impact of parenteral imipenem/cilastatin therapy on the bowel flora of six patients was evaluated. Stool samples were collected before and during therapy and qualitative and quantitative bacteriologic studies were performed. Imipenem had no effect on total microorganism counts. Two patients acquired Candida albicans during therapy, and three patients acquired Proteus species. Pseudomonas species in one patient acquired resistance. Imipenem appears to have a relatively modest effect on the bowel flora and apparently does not readily induce resistance in the resident flora as compared with other agents.

Pharmacokinetics of imipenem and cilastatin in patients with cystic fibrosis

The pharmacokinetics of imipenem, a new carbapenem antibiotic, and cilastatin, a metabolic inhibitor, were evaluated in 17 patients with cystic fibrosis. Imipenem and cilastatin were combined in a ratio of 1:1 in the infusion solution, and patients intravenously received 30, 60, or 90 mg of imipenem per kg of body weight per day, divided into four equal doses. Pharmacokinetic evaluation after the first dose and again under steady-state conditions revealed biodisposition characteristics which were similar and independent of the daily dose administered. Cilastatin concentrations in serum paralleled those of imipenem. A linear relationship between dose and area under the serum concentration-time curve for both compounds was observed, suggesting a first-order pharmacokinetic process. A total of 50 and 78% of the doses of imipenem and cilastatin, respectively, were recovered unchanged in the urine. The renal clearances of imipenem and cilastatin averaged 54 and 88%, respectively, of the serum clearance. These data suggest that an extrarenal mechanism may be involved in the overall elimination of imipenem. No patient experienced any clinical or biochemical abnormalities during drug therapy.

In vitro activity of imipenem--a review

A review is given of the microbiological properties of imipenem, a new carbapenem antibiotic with an exceptionally broad spectrum of antibacterial activity. An evaluation of results of numerous in vitro studies reveals that imipenem effectively inhibited growth of 53 of 55 bacterial species, the mean MIC90 being less than 8 mg/l. The MIC90 for cocci, with the exception of Staphylococcus epidermidis, is in the range of 0.01-3.1 mg/l. The MIC90 for all Enterobacteriaceae is equal to or less than 8 mg/l. Pseudomonas aeruginosa and other non-fermentative gram-negative bacteria are generally susceptible to imipenem, only Pseudomonas maltophilia and Pseudomonas cepacia showing intrinsic resistance. Imipenem is currently the most active drug available against anaerobic bacteria, the MIC usually being below 1 mg/l even for Bacteroides fragilis. Rare bacteria such as Nocardia asteroides, Listeria monocytogenes or fast growing Mycobacterium spp. which cause difficult-to-treat infections are also susceptible to imipenem. Increases in inoculum size have only a minimal effect on activity of the drug. In most species the MBC only slightly exceeded the MIC; however in the case of Streptococcus faecalis the MBC value was many times the MIC value. Synergism has been observed in combinations of imipenem with aminoglycosides, and antagonism in combinations with other beta-lactam antibiotics against Pseudomonas aeruginosa and Serratia marcescens. Imipenem is stable in the presence of the common chromosomal and plasmid-mediated enzymes. Induction of inactivating enzymes was observed in staphylococci, Pseudomonas aeruginosa and Serratia marcescens.