What is Doxylamine?
Doxylamine is a first-generation antihistamine, a class of drugs that blocks the action of histamine in the body [1.4.5]. Its primary effects are sedation and reducing allergy symptoms like sneezing and runny nose [1.4.5]. Due to its strong sedative properties, it is a common active ingredient in over-the-counter (OTC) sleep aids, such as Unisom SleepTabs [1.6.1]. It also possesses anticholinergic properties, which can lead to side effects like dry mouth, constipation, and urinary retention [1.2.3]. In pharmacology, its most notable use beyond a sleep aid is in combination with pyridoxine (vitamin B6) to treat nausea and vomiting of pregnancy (NVP) [1.3.1]. This combination has been extensively studied and is available by prescription under brand names like Diclegis and Bonjesta [1.6.5, 1.8.5].
Can Doxylamine Affect Babies During Pregnancy?
Extensive research has found that the combination of doxylamine and pyridoxine is not associated with an increased risk of birth defects or major malformations when used during pregnancy [1.3.2, 1.3.5]. Numerous meta-analyses and cohort studies have corroborated its safety for the fetus [1.3.3, 1.3.4]. In fact, the FDA has granted the doxylamine-pyridoxine combination a Pregnancy Category A status, which is the safest category reserved for drugs where well-controlled studies in humans have failed to show a risk to the fetus [1.8.2, 1.8.3]. The American College of Obstetricians and Gynecologists (ACOG) recommends it as a first-line pharmacologic treatment for NVP when lifestyle and dietary changes are not enough [1.3.4]. Studies have also shown that its use does not increase the risk of other pregnancy-related issues like preterm delivery or low birth weight [1.5.5].
Can Doxylamine Affect Babies During Breastfeeding?
Doxylamine's use while breastfeeding requires more caution. The drug is expected to pass into human breast milk due to its low molecular weight [1.2.2, 1.4.4]. While small, occasional doses are not expected to cause adverse effects, larger or prolonged doses may pose risks to the nursing infant [1.4.1, 1.7.4].
Potential effects on a breastfed baby include:
- Sedation and Drowsiness: As a sedative, doxylamine can make the infant sleepy [1.4.2].
- Irritability and Excitement: Paradoxically, some infants may experience excitement or irritability [1.2.2, 1.4.4].
- Decreased Milk Supply: Higher doses of antihistamines may potentially decrease the mother's milk supply, especially when lactation is not yet well-established or if taken with a decongestant like pseudoephedrine [1.4.1, 1.4.5].
Because of these potential adverse reactions, manufacturers of the combination doxylamine/pyridoxine product state it should not be used by nursing women [1.2.2]. Healthcare providers recommend a decision be made to either discontinue nursing or the drug, weighing the importance of the medication for the mother against the potential risks to the infant [1.4.4]. Infants with pre-existing conditions like apnea may be especially vulnerable to the sedative effects [1.2.2].
Direct Administration and Overdose Risk in Infants
Giving doxylamine products directly to children, especially those under two years of age, is strongly discouraged and dangerous. The FDA has issued warnings against using OTC cough and cold products containing antihistamines like doxylamine in children under two due to the risk of serious side effects, including death [1.9.1]. Some manufacturers have voluntarily updated labeling to recommend against use in children under four [1.9.1].
An overdose of doxylamine in a child can lead to severe anticholinergic toxicity, with symptoms such as [1.2.3, 1.9.3]:
- Coma
- Seizures
- Hyperthermia
- Cardiorespiratory arrest
There is a high risk of toxicity and death from overdose in children, as appropriate dosages for this age group have not been established [1.2.6, 1.9.1].
Comparison of Doxylamine and Other Antihistamines
When considering an antihistamine during pregnancy or breastfeeding, it's helpful to compare doxylamine with other common options.
| Feature | Doxylamine (e.g., Unisom) | Diphenhydramine (e.g., Benadryl) | Loratadine (e.g., Claritin) |
|---|---|---|---|
| Generation | First-Generation (Sedating) | First-Generation (Sedating) | Second-Generation (Non-Sedating) |
| Pregnancy Safety | Category A (in combination with B6); extensive safety data [1.8.3]. Considered safe [1.6.2]. | Considered safe for use during pregnancy [1.6.2]. | Fewer data than first-generation, but studies are reassuring [1.7.1]. |
| Breastfeeding Safety | Use with caution. Can cause infant sedation or irritability and may reduce milk supply in high doses [1.2.1, 1.4.4]. | Use with caution. Similar concerns for sedation and potential milk supply reduction as doxylamine. | Generally preferred over sedating antihistamines as less is transferred to milk and sedation is not a concern. |
| Primary Use | Sleep aid, morning sickness (with B6) [1.3.1]. | Allergies, sleep aid [1.6.2]. | Allergies. |
Conclusion
The answer to whether doxylamine can affect babies is nuanced and highly dependent on the method of exposure. During pregnancy, doxylamine, particularly when combined with vitamin B6, has a strong safety profile and is a recommended treatment for morning sickness [1.8.3]. However, the situation changes during lactation, where the drug passes into breast milk and carries a risk of sedation and other side effects for the infant, warranting caution and medical consultation [1.4.1]. Finally, direct administration to infants and young children is dangerous and carries a risk of severe overdose and toxicity [1.9.1]. Always consult a healthcare provider before using any medication during pregnancy or while breastfeeding.
For more detailed information on specific drugs and their use during lactation, a valuable resource is the Drugs and Lactation Database (LactMed®) from the National Institutes of Health. [1.2.1]
