Teratogenic Effects. Pregnancy Category C
Codeine – A study in rats and rabbits
reported no teratogenic effect of codeine administered during the period of
organogenesis in doses ranging from 5 to 120 mg/kg. In the rat, doses at the 120
mg/kg level, in the toxic range for the adult animal, were associated with an
increase in embryo resorption at the time of implantation. In another study a
single 100 mg/kg dose of codeine administered to pregnant mice reportedly
resulted in delayed ossification in the offspring.
There are no adequate and well-controlled studies in pregnant women.
Acetaminophen and codeine phosphate should be used during pregnancy only if the
potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects
Dependence has been reported in newborns whose mothers took
opiates regularly during pregnancy. Withdrawal signs include irritability,
excessive crying, tremors, hyperreflexia, fever, vomiting, and diarrhea. These
signs usually appear during the first few days of life.
Labor and Delivery
Narcotic analgesics cross the placental barrier. The closer to
delivery and the larger the dose used, the greater the possibility of
respiratory depression in the newborn. Narcotic analgesics should be avoided
during labor if delivery of a premature infant is anticipated. If the mother has
received narcotic analgesics during labor, newborn infants should be observed
closely for signs of respiratory depression. Resuscitation may be required (see OVERDOSAGE). The effect of codeine,
if any, on the later growth, development, and functional maturation of the child
is unknown.
Nursing Mothers
Acetaminophen is excreted in breast milk in small amounts, but
the significance of its effects on nursing infants is not known. Because of the
potential for serious adverse reactions in nursing infants from acetaminophen, a
decision should be made whether to discontinue the drug, taking into account the
importance of the drug to the mother.
Codeine is secreted into human milk. In women with normal codeine metabolism
(normal CYP2D6 activity), the amount of codeine secreted into human milk is low
and dose-dependent. Despite the common use of codeine products to manage
postpartum pain, reports of adverse events in infants are rare. However, some
women are ultra-rapid metabolizers of codeine. These women achieve
higher-than-expected serum levels of codeine's active metabolite, morphine,
leading to higher-than-expected levels of morphine in breast milk and
potentially dangerously high serum morphine levels in their breastfed infants.
Therefore, maternal use of codeine can potentially lead to serious adverse
reactions, including death, in nursing infants.
The prevalence of this CYP2D6 phenotype varies widely and has been estimated
at 0.5 to 1% in Chinese and Japanese, 0.5 to 1% in Hispanics, 1 to 10% in
Caucasians, 3% in African Americans, and 16 to 28% in North Africans, Ethiopians
and Arabs. Data is not available for other ethnic groups.
The risk of infant exposure to codeine and morphine through breast milk
should be weighed against the benefits of breastfeeding for both the mother and
baby. Caution should be exercised when codeine is administered to a nursing
woman. If a codeine containing product is selected, the lowest dose should be
prescribed for the shortest period of time to achieve the desired clinical
effect. Mothers using codeine should be informed about when to seek immediate
medical care and how to identify the signs and symptoms of neonatal toxicity,
such as drowsiness or sedation, difficulty breastfeeding, breathing
difficulties, and decreased tone, in their baby. Nursing mothers who are
ultra-rapid metabolizers may also experience overdose symptoms such as extreme
sleepiness, confusion or shallow breathing. Prescribers should closely monitor
mother-infant pairs and notify treating pediatricians about the use of codeine
during breastfeeding (see PRECAUTIONS, General, Ultra-rapid Metabolizers of Codeine).