Diphenhydramine

Brand names

• Acetaminophen-PM
• Allerdryl
• Allernix
• Allermax
• Anacin PM
• Banophen
• Benadryl
• Benahist
• Benylin
• Caladryl [CD]
• Compoz
• Dermarest
• Di-Delamine
• Dihydrex
• Diphendryl
• Diphenhist
• Diphenhydramine
• Gecil
• Genahist
• Hydramine
• Insomnal
• Kolex
• Medi-Phedryl
• Midol-PM
• Nytol
• PMS-Diphenhydramine
• Sominex
• Twilite
• Tylenol PM Extra Strength
• Valdrene
• Wal-Ben
• Wal-Dryl
• Wehydryl

Usage

For allergic reactions such as hay fever, itching skin, and hives; motion sickness; and sleeping difficulty.

How it works

It blocks the effects of histamine, a naturally occurring substance that causes swelling, itching, sneezing, and watery eyes.

Side effects

Serious

No serious side effects are associated with this medicament.

Common

Drowsiness, dry mouth, nausea, thickening of mucus.

Less common

Confusion, difficult urination, blurred vision.

Possible interactions

Other medicaments:

Diphenhydramine may increase the effects of:

• all medicaments with a sedative effect such as benzodiazepines, tricyclic antidepressants and narcotics and cause over sedation.
• amitriptyline (Elavil) and cause increased urinary retention.
• atropine and atropinelike medicaments.
• tramadol (Ultram), leading to increased sedation risk.

The following medicaments may increase the effects of diphenhydramine:



• monoamine oxidase (MAO) type A inhibitor medicaments; can delay elimination, exaggerating and prolonging its action.

Diphenhydramine taken concurrently with:



• phenothiazines may result in increased difficulty urinating, intestinal obstruction or glaucoma, especially in those over 70 years old.
• temazepam (Restoril) in pregnancy may increase risk of death of the fetus.
• tricyclic antidepressants may cause increased risk of urinary retention.

Herbal medicines or minerals:

Valerian and kava kava may interact additively (drowsiness). Avoid these combinations. Ginkgo biloba leaf extract has a German Commission E indication for vertigo, but has not been studied in combination with antihistamines and cannot presently be recommended.

Alcohol:

The combination of alcohol and antihistamines can cause rapid and marked sedation.

Marijuana smoking:

Increased drowsiness and mouth dryness; accentuation of impaired thinking.

Exposure to sun:

Caution-this medicament may cause photosensitivity.

Exposure to environmental chemicals:

The insecticides Aldrin, Dieldrin and Chlordane may decrease the effectiveness of this medicament. Sevin may increase the sedative effects of this medicament.