Methadone and heroin during pregnancy: a review of behavioral effects in human and animal offspring.

Both clinical and animal studies indicate that prenatal exposure to opiate produces effects that occur in two phases. An acute phase consists of a neonatal abstinence syndrome characterized by increased CNS arousal. The major behavior symptoms seen in both humans and animals include hyperactivity, disturbed sleep and increased lability of state. This early phase can be quite prolonged, lasting from 12 weeks hyperactivity, disturbed sleep and increased lability of state. This early phase can be quite prolonged, lasting from 12 weeks to six months in humans and 20-25 days in rats. Although confirming pharmacokinetic studies are needed, it is possible that these persistent symptoms result from the slow clearance of the drug from neonatal tissues. The second phase of the syndrome is less well-understood but the available clinical evidence suggests that exposure to heroin, particularly in a pattern of polydrug abuse, can result in impaired organizational and perceptual abilities, poor self-adjustment and in situations requiring motor inhibition, heightened activity. Studies of pre-school children exposed prenatally to methadone, show no effects on intellectual and cognitive functioning but do reveal heightened activity or energy level, impulsivity, and brief attention span and persistence. A finding of impaired motor inhibition while performing a task has been stressed by one worker as an area of particular vulnerability among these children. A strikingly similar effect, characterized as an impaired ability to modulate task-oriented motor activity, has been described for adult rats prenatally exposed to methadone.