Diphenhydramine / phenylephrine Pregnancy and Breastfeeding Warnings

Brand names: Alahist LQ, Aldex-CT, Benadryl Allergy Plus Congestion, Benadryl Children's Allergy Plus Congestion, Benadryl-D Allergy Plus Sinus, Benadryl-D Children's Allergy & Sinus, Children's Triacting Night Time, D-Tann, Delsym Children's Night Time Cough & Cold, Dimetapp Children's Nighttime Cold & Congestion, Dimetapp Nighttime Cold and Congestion, Diphenmax D, Diphentann-D, Dytan-D, PediaCare Children's Allergy & Cold, PediaCare Nighttime Multi-Symptom Cold, Pediatex-CT, Robitussin Night Time Cough & Cold, Sudafed PE Sinus Congestion Nighttime, Theraflu Thin Strips Nighttime Cold and Cough, Triaminic Night Time Cold & Cough, Triaminic Thin Strips Night Time Cold & Cough, Uni-Tann D

Medically reviewed by Drugs.com. Last updated on Aug 1, 2023.

Diphenhydramine / phenylephrine Pregnancy Warnings

The manufacturer makes no recommendation regarding use during pregnancy.

AU TGA pregnancy category: B2
US FDA pregnancy category: Not assigned

Comments:
-According to some authorities, diphenhydramine is compatible with pregnancy and may be the drug of choice if parenteral antihistamines are needed in pregnancy, however one case-controlled study showed association with cleft palate, and premature infants exposed within 2 weeks of birth risk toxicity.
-Phenylephrine is a sympathomimetic used in emergencies to treat hypotension and alleviate eye and ear allergic symptoms.
-Phenylephrine could cause constriction in uterine vessels (that are normally maximally dilated during pregnancy), reducing uterine blood flow, potentially causing fetal hypoxia.
-Phenylephrine may interact with oxytocic or ergot derivatives to cause persistent maternal hypertension; cerebral vessel rupture is possible.
-Sympathomimetic amines are teratogenic in some animal models, but are not suspected to cause human teratogenicity.

Animal studies are not available for the combination product. There are no controlled data in human pregnancy.

Diphenhydramine: Animal studies at doses up to 5 times the human dose showed no fetal toxicity or fertility impairment. Placental transfer was seen in sheep after a 100 mg intravenous dose with a fetal:maternal ratio of 0.85, peaking within 5 minutes. A monitoring study including 595 mother-child pairs that had first trimester diphenhydramine exposure showed no increase in major or minor malformations; 2948 any time pregnancy exposures showed no increase in major or minor malformations; unconfirmed possible associations include 3 hypospadia cases and 5 other genitourinary malformations, 3 eye and ear defects, 3 syndromes other than Down's, 13 inguinal hernias, 5 clubfoot cases, 5 diaphragm malformations, and 5 ventricular septal defects (any, opening or closing). A case control study of 599 first semester diphenhydramine exposures showed a statistical association with cleft palate; other studies have not found an association with cleft palate or have shown a decrease.

Phenylephrine: A monitoring study including 1249 mother-child pairs that had first trimester phenylephrine exposure showed an increase in malformation, with association greater with minor defects than major defects (8 eye and ear defects, 6 syndactyly, 4 preauricular skin tags, and 3 clubfoot cases); 4149 any time pregnancy exposures were associated with 15 congenital dislocation of the hip, 6 umbilical hernia, and 4 other musculoskeletal defects. Placental transfer is likely with phenylephrine's low molecular weight (about 167).

AU TGA pregnancy category B2: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

See references

Diphenhydramine / phenylephrine Breastfeeding Warnings

Use is not recommended.

Excreted into human milk: Yes (diphenhydramine)/ Data not available (phenylephrine)
Excreted into animal milk: Data not available (phenylephrine)

Comments:
-One old biologic assay showed diphenhydramine in breast milk in some women after a 100 mg intramuscular dose; no studies using modern assays are available.
-According to some authorities, occasional, small diphenhydramine doses are not expected to adversely affect breastfeeding infants, but large or prolonged dosing may decrease the milk supply, especially in combination with a sympathomimetic amine (e.g. pseudoephedrine) or if lactation is not well established, and may have effects on the infant.
-Administering diphenhydramine after the last feeding of the day may minimize effects on the infant, but non-sedating antihistamines are preferred.
-Phenylephrine oral bioavailability is about 40%, making it unlikely an infant would receive large doses from breast milk.
-Phenylephrine may decrease milk production.

See references