Acetaminophen / chlorpheniramine Pregnancy and Breastfeeding Warnings
Acetaminophen / chlorpheniramine Pregnancy Warnings
Acetaminophen has not been formally assigned to a pregnancy category by the FDA. It is routinely used for short-term pain relief and fever in all stages of pregnancy. Acetaminophen is believed to be safe in pregnancy when used intermittently for short durations. Chlorpheniramine has been assigned to pregnancy category B by the FDA. Animal studies have not been reported. There are no controlled data in human pregnancy. Acetaminophen-chlorpheniramine is only recommended for use during pregnancy when benefit outweighs risk.
Two cases of acetaminophen overdose in late pregnancy have been reported. In both cases neither the neonate nor the mother suffered hepatic toxicity. Investigations have revealed conflicting results with regards to the pharmacokinetic disposition of acetaminophen in pregnant women. One study has suggested that the oral clearance of acetaminophen is 58% higher and the elimination half-life is 28% longer in pregnant women compared to nonpregnant women. Another study has suggested that the elimination half-life is not different in patients who are pregnant. That study also suggested that the volume of distribution of acetaminophen may be higher in pregnant women. One study has suggested that acetaminophen in typical oral doses may result in a reduced production of prostacyclin in pregnant women. That study also suggested that acetaminophen does not affect thromboxane production. The Collaborative Perinatal Project monitored 1,070 first trimester exposures and 3,931 exposures which occurred anytime during pregnancy. No evidence was found to suggest a relationship to large categories of malformations. Antihistamine exposure in the first trimester in general was not associated with an increased risk of malformations.
Acetaminophen / chlorpheniramine Breastfeeding Warnings
One small study has reported that following a 1000 mg dose of acetaminophen to nursing mothers, nursing infants receive less than 1.85% of the weight-adjusted maternal oral dose.
Acetaminophen is excreted into human milk in small concentrations. One case of a rash has been reported in a nursing infant. Acetaminophen is considered compatible with breast-feeding by the American Academy of Pediatrics. There are no data on the excretion of chlorpheniramine into human milk. Because other antihistamines are excreted into human milk in low concentrations, the manufacturer recommends that caution be used when administering chlorpheniramine to nursing women.
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