Acetaminophen / diphenhydramine Pregnancy and Breastfeeding Warnings

Acetaminophen / diphenhydramine is also known as: Aceta-Gesic, Acetadryl, Acetaminophen PM Extra Strength, Coricidin Night Time Cold Relief, Counteract PM Extra Strength, Excedrin PM, Genapap PM, Headache Formula PM, Headache Relief PM, Legatrin PM, Mapap PM, Midol PM, Night Time Pain, Non-Aspirin PM Extra Strength, Pain Relief PM Extra Strength, Pain Reliever PM, Percogesic Extra Strength, Percogesic Original Strength, Pharbetol PM, Sominex Pain Relief Formula, Tylenol PM, Tylenol Severe Allergy, Tylenol Sore Throat Nighttime, Unisom PM Pain, Wal-Nadol PM Extra Strength

Acetaminophen / diphenhydramine Pregnancy Warnings

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. A review of prenatal drug use in 3026 women with premature infants demonstrated an increased risk of retrolental fibroplasia with antihistamine use during the last two weeks of pregnancy. The dosage used or the particular antihistamine was not specified. The incidence of retrolental fibroplasia in premature infants exposed in utero to antihistamine during this time was 21% compared to 11% in premature infants not exposed. Diphenhydramine has been shown to have oxytocic effects in animal and human uteri. One case report of a pregnant woman who ingested a large amount of diphenhydramine in an attempted suicide developed strong, regular uterine contractions that were halted by the administration of intravenous magnesium.

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. Acetaminophen should only be given during pregnancy when need has been clearly established. Diphenhydramine has been assigned to pregnancy category B by the FDA. Animal studies have failed to reveal teratogenicity. The Collaborative Perinatal Project reported 595 first-trimester exposures and 2,948 exposures anytime during pregnancy. No relationship was found to large categories of malformations. Possible associations with individual malformation were found. One study reported a statistical relationship between diphenhydramine use in the first trimester and cleft palate. One case of withdrawal in an infant whose mother ingested 150 mg per day of diphenhydramine has been reported. This infant developed tremor on the fifth day of life which was treated with phenobarbital. Acetaminophen-diphenhydramine is only recommended for use during pregnancy when benefit outweighs risk.

Acetaminophen / diphenhydramine 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. Diphenhydramine is excreted into human milk. Diphenhydramine may also inhibit lactation. The manufacturer recommends that due to the potential for serious adverse reactions in nursing infants, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

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