Risk Summary

Embryonic loss was observed in monkeys treated with imipenem/cilastatin, and fetal abnormalities were observed in relebactam-treated mice; therefore, advise pregnant women of the potential risks to pregnancy and the fetus. There are insufficient human data to establish whether there is a drug-associated risk for major birth defects, miscarriage, or adverse maternal or fetal outcomes with RECARBRIO, imipenem, cilastatin, or relebactam in pregnant women.

Developmental toxicity studies with imipenem and cilastatin (alone or in combination) administered parenterally during organogenesis to mice, rats, rabbits, and monkeys at doses 1 to 5 times the maximum recommended human dose (MRHD of imipenem 500 mg/cilastatin 500 mg every 6 hours for total daily doses of imipenem 2000 mg/cilastatin 2000 mg) based on body surface area comparison, showed no drug-induced fetal malformations. Embryofetal development studies with imipenem/cilastatin administered to cynomolgus monkeys at doses similar to the MRHD (based on body surface area comparison) showed an increase in embryonic loss. In an embryofetal study, parental administration of relebactam to pregnant mice during the period of organogenesis was associated with a non-dose responsive increase in the litter incidence of cleft palate at a plasma relebactam exposure approximately equal to the human exposure at the MRHD (250 mg every 6 hours for a daily dose of 1000 mg) and an increased percent litter incidence of total skeletal malformations at a plasma exposure approximately 6 times the human exposure at the MRHD. Reproductive studies with relebactam administered parenterally to pregnant rats and rabbits during the period of organogenesis at plasma exposures up to 7 and 24 times, respectively, the plasma exposure in humans at the MRHD showed no adverse effects on pregnancy or embryofetal development. Relebactam administered to rats during gestation through lactation was not associated with fetal toxicity, developmental delays, or impaired reproduction in first generation offspring at plasma exposures equivalent to 8 times the human exposure at the MRHD (see Data).

The background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. The estimated background risk of major birth defects is 2 to 4% and miscarriage is 15 to 20% of clinically recognized pregnancies within the U.S. general population.

Data

Animal Data

Imipenem and Cilastatin

Reproductive toxicity studies with imipenem and cilastatin (alone or in combination) administered parenterally to mice, rats, and rabbits showed no evidence of effects on embryofetal (mice, rats, and rabbits) or pre/postnatal (rats) development. In embryofetal development studies, imipenem was administered intravenously to rats (gestation days (GD) 7 to 17), and rabbits (GD 6 to 18), at doses up to 900 and 60 mg/kg/day, respectively, approximately 4 and 0.6 times the MRHD (based on body surface area comparison). Cilastatin was administered subcutaneously to rats (GD 6 to 17) and intravenously to rabbits (GD 6 to 18) at doses up to 1000 and 300 mg/kg/day, respectively, approximately 5 and 3 times the MRHD (based on body surface area comparison). Imipenem/cilastatin was administered intravenously to mice at doses up to 320 mg/kg/day (GD 6 to 15) which is approximately equivalent to the MRHD based on body surface area comparison, and to rats at intravenous doses up to 80 mg/kg/day and a subcutaneous dose of 320 mg/kg/day (GD 6 to 17). In a separate pre-postnatal development study, rats were administered subcutaneous imipenem/cilastatin at doses up to 320 mg/kg/day (GD 15 to day 21 postpartum). The subcutaneous dose of 320 mg/kg/day in rats is approximately double the MRHD based on body surface area comparison.

Imipenem/cilastatin administered intravenously to pregnant cynomolgus monkeys during organogenesis (GD 21 to 50) at 100 mg/kg/day, a dose approximately equivalent to the MRHD (based on body surface area comparison), at an infusion rate mimicking human clinical use was not associated with fetal malformations, but there was an increase in embryonic loss relative to controls. Imipenem/cilastatin administered to pregnant cynomolgus monkeys during organogenesis at 40 mg/kg/day by bolus intravenous injection caused significant maternal toxicity including death and embryofetal loss.

Relebactam

In an embryofetal development study in pregnant mice, relebactam administered subcutaneously in doses of 80, 200, and 450 mg/kg/day during the period of organogenesis (GD 6 to 17) was not associated with maternal toxicity at doses up to 450 mg/kg/day. However, although individual skeletal malformations appeared only as single occurrences in the high dose group, the percent litter incidence of total skeletal malformations (skull and vertebral) was increased in the high-dose group (21% litter incidence) compared to the concurrent control value (5.3% litter incidence). The plasma relebactam exposure for the high dose associated with increased skeletal malformations was approximately 6 times greater than the human plasma exposure at the MRHD based on AUC comparison. Also, mice receiving the lowest administered dose of relebactam, 80 mg/kg/day, exhibited a higher percent litter incidence (15% litter incidence) of cleft palate (a rare malformation in mice) compared to the concurrent control value (0% litter incidence) and historical control values (up to 11% litter incidence). This finding did not increase in a dose-dependent manner with percent litter incidences of 0% and 5.3% in the mid- and high-dose groups respectively. The plasma AUC exposure for the low dose of relebactam associated with increased cleft palate was approximately equivalent to the human plasma AUC at the MRHD. In embryofetal development studies in rats and rabbits, intravenous relebactam was administered to rats in doses of 50, 150, and 450 mg/kg/day and rabbits in doses of 35, 275, and 450 mg/kg/day. In these studies, relebactam administered during the period of organogenesis to pregnant rats (GD 6 to 20) and rabbits (GD 7 to 20) was not associated with maternal or embryofetal toxicity at doses up to 450 mg/kg/day corresponding to plasma AUC exposures of approximately 7 and 24 times, respectively, the human plasma AUC at the MRHD. 

In a pre-postnatal development study, relebactam administered intravenously in doses of 65, 200, and 450 mg/kg/day to rats from GD 6 to lactation day (LD) 20 produced no maternal toxicity and did not impair the physical and behavioral development or reproduction in first generation offspring at doses up to 450 mg/kg/day corresponding to a plasma AUC exposure of approximately 8 times the plasma AUC exposure in humans at the MRHD.

Studies in pregnant rats and rabbits showed that relebactam is transferred to the fetus through the placenta, with fetal plasma concentrations up to 5% to 6% of maternal concentrations observed on GD 20.