Diphenhydramine

Diphenhydramine is an antihistamine used to relieve allergic rhinitis (seasonal allergy) symptoms including sneezing, runny nose, itching, and watery eyes and to relieve itching and swelling associated with uncomplicated allergic skin reactions. It is also used as a short-term sleep aid, to control coughs due to colds or allergy, and to prevent/treat motion sickness. Diphenhydramine is available in nonprescription products alone and in combination with other nonprescription drugs, to treat symptoms of allergy, colds, and upper respiratory infections.

Safetychecker Summary for Diphenhydramine
(for details about the summarized interactions, read the full article)

Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	Henbane*
Depletion or interference	None known
Side effect reduction/prevention	None known
Supportive interaction	None known
Reduced drug absorption/bioavailability	None known

Interactions with Herbs

Henbane (Hyoscyamus niger)
Antihistamines, including diphenhydramine, can cause “anticholinergic” side effects such as dryness of mouth and heart palpitations. Henbane also has anticholinergic activity and side effects. Therefore, use with diphenhydramine could increase the risk of anticholinergic side effects,¹ though apparently no interactions have yet been reported with diphenhydramine and henbane. Henbane should not be taken except by prescription from a physician trained in its use, as it is extremely toxic.

Interactions with Foods and Other Compounds

Alcohol
Diphenhydramine causes drowsiness.² Alcohol may intensify this effect and increase the risk of accidental injury.³ To prevent problems, people taking diphenhydramine or diphenhydramine-containing products should avoid alcohol.

References:

1. Blumenthal M, ed. The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998, 146.

2. Threlkeld DS, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 191a–1b.

3. Threlkeld DS, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 191a–1b.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2003.