Risk Summary

Available data from clinical trials on the use of Moxidectin Tablets in pregnant women are insufficient to establish whether there is a moxidectin-associated risk for major birth defects and miscarriage . Moxidectin administered orally to pregnant rats during the period of organogenesis was not associated with significant embryo-fetal developmental effects at doses of approximately 15 times the recommended human dose based on body surface area (BSA) comparison. When moxidectin was dosed orally to pregnant rabbits during the period of organogenesis, no embryo-fetal developmental effects were observed at oral doses of moxidectin up to 24 times the recommended human dose based on BSA comparison (see Data). 

Daily administration of moxidectin by oral gavage to maternal female rats during organogenesis and through lactation was associated with decreased survival, adverse clinical signs, and decreased body weights in first-generation offspring during the lactation period at a moxidectin dose less than 2-times the recommended human dose based on BSA comparison. Additional findings in first-generation offspring at the same dose included delays in pinna unfolding, eye opening, and vaginal opening. Other parameters, including reproduction and neurological development in first-generation offspring were not affected at any moxidectin dose (see Data). 

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

Data

Animal Data

In a rat embryo-fetal development study, daily oral administration of moxidectin at 12 mg/kg/day (approximately 15 times the recommended human dose of 8 mg based on BSA comparison) during Gestation Days (GDs) 6 to 15 significantly increased the fetal incidence, but not the litter incidence of cleft palate and the fetal and litter incidence of a skeletal variation, wavy ribs, at a maternally toxic dose. Mean maternal food consumption, body weights, and body weight gain were significantly decreased at moxidectin doses of 10 and 12 mg/kg/day compared to control values. The no observed adverse effect level (NOAEL) value for maternal and fetal toxicity was considered to be 5 and 10 mg/kg/day respectively (approximately 6 and 12 times, respectively, the recommended human dose based on BSA comparison). In the rabbit, daily oral administration of moxidectin at ≥ 5 mg/kg/day from GD 7 to GD 19 was not associated with fetal weight loss or malformations but resulted in significantly decreased maternal food consumption and body weight gains. The NOAEL values for maternal and fetal toxicity in the rabbit was 1 mg/kg/day and 10 mg/kg/day respectively (approximately 2 times and 24 times, respectively, the recommended human dose based on BSA comparison). 

In a pre-postnatal study, moxidectin doses of 0.2 and 0.5 mg/kg/day were administered by oral gavage to maternal female rats from GD 6 throughout the lactation period until LD 21. A third dose group that received maternal doses of 1.5 mg/kg/day moxidectin (less than 2-times the recommended human dose based on BSA comparison) was divided into two cohorts with Cohort 1 receiving maternal doses from GD 6 until LD 10 and Cohort 2 receiving maternal doses from GD 6 until each individual animal littered, but not during the lactation period. First-generation offspring in Cohort 1 had adverse clinical signs (small body size, thin, weak, subdued/sluggish, pale, cold to touch, respiratory distress, blue coloration and/or no visible milk in stomach) and decreased survival and body weights during the lactation period. However, first-generation offspring in Cohort 2 did not experience adverse clinical signs, body weight loss, or reduced survival suggesting moxidectin in lactation milk was responsible for the adverse effects in offspring in Cohort 1. Additional findings included delays in pinna unfolding and eye opening in male and female offspring in both cohorts and delay of vaginal opening in female offspring in Cohort 2. No adverse effects were noted in offspring at a maternal dose of 0.5 mg/kg/day (approximately 0.6 times the recommended human dose based on BSA comparison). Reproductive performance based on mating and fertility indices and neurological development were not affected in male and female first-generation offspring at any of the administered moxidectin doses.

In another pre-postnatal study in rats, parental oral administration of dietary moxidectin prior to mating, through mating, gestation, and lactation did not produce adverse effects in first-generation or second-generation offspring at a maternal NOAEL dose of 0.824 mg/kg/day (approximately equivalent to the recommended human dose based on BSA comparison). However, at moxidectin doses ≥ 1.1 mg/kg/day (approximately equivalent to 1.3 times the recommended human dose based on BSA comparison), the survival and body weights of first-generation offspring were significantly decreased during the lactation period, and the number of live fetuses at birth was significantly decreased with a maternal moxidectin dose of 11 mg/kg/day (approximately equivalent to 13 times the recommended human dose based on BSA comparison). In this study, offspring were assessed for survival, body weights, and fertility, and developmental milestones were not assessed.