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SERIOUS AND OCCASIONALLY FATAL HYPERSENSITIVITY (anaphylactic) REACTIONS HAVE BEEN REPORTED IN PATIENTS RECEIVING THERAPY WITH BETA-LACTAMS. THESE REACTIONS ARE MORE LIKELY TO OCCUR IN INDIVIDUALS WITH A HISTORY OF SENSITIVITY TO MULTIPLE ALLERGENS. THERE HAVE BEEN REPORTS OF INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY WHO HAVE EXPERIENCED SEVERE REACTIONS WHEN TREATED WITH ANOTHER BETA-LACTAM. BEFORE INITIATING THERAPY WITH PRIMAXIN® I.M. (imipenem and cilastatin) , CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS, OTHER BETA-LACTAMS, AND OTHER ALLERGENS. IF AN ALLERGIC REACTION OCCURS, PRIMAXIN® SHOULD BE DISCONTINUED. SERIOUS ANAPHYLACTIC REACTIONS REQUIRE IMMEDIATE EMERGENCY TREATMENT WITH EPINEPHRINE. OXYGEN, INTRAVENOUS STEROIDS, AND AIRWAY MANAGEMENT, INCLUDING INTUBATION, MAY ALSO BE ADMINISTERED AS INDICATED.
Seizures and other CNS adverse experiences, such as myoclonic activity, have been reported during treatment with PRIMAXIN I.M. (See PRECAUTIONS and ADVERSE REACTIONS.)
Carbapenems, including imipenem, may reduce serum valproic acid concentrations to subtherapeutic levels, resulting in loss of seizure control. Serum valproic acid concentrations should be monitored frequently after initiating carbapenem therapy. Alternative antibacterial or anticonvulsant therapy should be considered if serum valproic acid concentrations drop below the therapeutic range or a seizure occurs (see PRECAUTIONS: DRUG INTERACTIONS).
Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including PRIMAXIN I.M., and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD.
Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.
Lidocaine HCl - Refer to the package circular for lidocaine HCl.
CNS adverse experiences such as myoclonic activity or seizures have been reported with PRIMAXIN I.M. These experiences have occurred most commonly in patients with CNS disorders (e.g., brain lesions or history of seizures) who also have compromised renal function. However, there were reports in which there was no recognized or documented underlying CNS disorder. Anticonvulsant therapy should be continued in patients with a known seizure disorder.
As with other antibiotics, prolonged use of PRIMAXIN I.M. may result in overgrowth of nonsusceptible organisms. Repeated evaluation of the patient's condition is essential. If superinfection occurs during therapy, appropriate measures should be taken.
Prescribing PRIMAXIN I.M. in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.
Caution should be taken to avoid inadvertent injection into a blood vessel. (See DOSAGE AND ADMINISTRATION) For additional precautions, refer to the package circular for lidocaine HCl.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long term studies in animals have not been performed to evaluate carcinogenic potential of imipenem-cilastatin. Genetic toxicity studies were performed in a variety of bacterial and mammalian tests in vivo and in vitro. The tests used were: V79 mammalian cell mutagenesis assay (imipenem-cilastatin sodium alone and imipenem alone), Ames test (cilastatin sodium alone and imipenem alone), unscheduled DNA synthesis assay (imipenem-cilastatin sodium) and in vivo mouse cytogenetics test (imipenem-cilastatin sodium). None of these tests showed any evidence of genetic alterations.
Reproductive tests in male and female rats were performed with imipenem-cilastatin sodium at intravenous doses up to 80 mg/kg/day and at a subcutaneous dose of 320 mg/kg/day, 2.1 times*** the maximum recommended daily human dose of the intramuscular formulation (on a mg/m2 body surface area basis). Slight decreases in live fetal body weight were restricted to the highest dosage level. No other adverse effects were observed on fertility, reproductive performance, fetal viability, growth, or postnatal development of pups.
Pregnancy: Teratogenic Effects
Pregnancy Category C: Teratology studies with cilastatin sodium at doses of 30, 100, and 300 mg/kg/day administered intravenously to rabbits and 40, 200, and 1000 mg/kg/day administered subcutaneously to rats, up to approximately 3.9 and 6.5 times*** the maximum recommended daily human dose (on a mg/m2 body surface area basis) of the intramuscular formulation of PRIMAXIN (25 mg/kg/day) in the two species, respectively, showed no evidence of adverse effects on the fetus. No evidence of teratogenicity was observed in rabbits given imipenem at intravenous doses of 15, 30, or 60 mg/kg/day and rats given imipenem at intravenous doses of 225, 450, or 900 mg/kg/day, up to approximately 0.8 and 5.8 times*** the maximum recommended daily human dose (on a mg/m2 body surface area basis) in the two species, respectively.
Teratology studies with imipenem-cilastatin sodium at intravenous doses of 20 and 80 and a subcutaneous dose of 320 mg/kg/day, approximately equal to (mice) and up to 2.1 times*** (rats) the maximum recommended daily intramuscular human dose (on a mg/m2 body surface area basis) in pregnant rodents during the period of major organogenesis, revealed no evidence of teratogenicity.
Imipenem-cilastatin sodium, when administered to pregnant rabbits subcutaneously at dosages above the usual human dose of the intramuscular formulation (1000-1500 mg/day), caused body weight loss, diarrhea, and maternal deaths. When comparable doses of imipenem-cilastatin sodium were given to non-pregnant rabbits, body weight loss, diarrhea, and deaths were also observed. This intolerance is not unlike that seen with other beta-lactam antibiotics in this species and is probably due to alteration of gut flora.
A teratology study in pregnant cynomolgus monkeys given imipenem-cilastatin sodium at doses of 40 mg/kg/day (bolus intravenous injection) or 160 mg/kg/day (subcutaneous injection) resulted in maternal toxicity including emesis, inappetence, body weight loss, diarrhea, abortion and death in some cases. In contrast, no significant toxicity was observed when non-pregnant cynomolgus monkeys were given doses of imipenem-cilastatin sodium up to 180 mg/kg/day (subcutaneous injection). When doses of imipenem-cilastatin sodium (approximately 100 mg/kg/day or approximately 1.3 times*** the maximum recommended daily human dose of the intramuscular formulation) were administered to pregnant cynomolgus monkeys at an intravenous infusion rate which mimics human clinical use, there was minimal maternal intolerance (occasional emesis), no maternal deaths, no evidence of teratogenicity, but an increase in embryonic loss relative to the control groups.
No adverse effects on the fetus or on lactation were observed when imipenem-cilastatin sodium was administered subcutaneously to rats late in gestation at dosages up to 320 mg/kg/day, 2.1 times the maximum recommended daily human dose (on a mg/m2 body surface area basis).
There are, however, no adequate and well-controlled studies in pregnant women. PRIMAXIN I.M. should be used during pregnancy only if the potential benefit justifies the potential risk to the mother and fetus.
It is not known whether imipenem-cilastatin sodium or lidocaine HCl (diluent) is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when PRIMAXIN I.M. is administered to a nursing woman.
Safety and effectiveness in pediatric patients below the age of 12 years have not been established.
Clinical studies of PRIMAXIN I.M. did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects; however, clinical studies of PRIMAXIN I.V. in a sufficient number of subjects aged 65 and over have not revealed overall differences in safety or effectiveness between these subjects and younger subjects (refer to the package circular for PRIMAXIN I.V.). Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function. Dosage adjustment in the case of renal impairment is necessary (see DOSAGE AND ADMINISTRATION, Adults With Impaired Renal Function).
***Based on patient body surface area of 1.6 m2 (weight of 60 kg).This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 8/19/2008
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