No drug-related teratogenic effects were observed in progeny of mice (up to 140 mg/kg or 420 mg/m2), rats (up to 80 mg/kg or 480 mg/m2) or rabbits (up to 300 mg/kg or 3600 mg/m2) treated with tramadol by various routes. Embryo and
fetal toxicity consisted primarily of decreased
fetal weights, skeletal ossification and increased supernumerary ribs at maternally toxic dose levels. Transient delays in developmental or behavioral parameters were also seen in pups from rat dams allowed to deliver.