diphenhydramine

Diphenhydramine (Benadryl) is an antihistamine used for treatingallergicreactions. Histamine is released by the body during several types of allergic reactions and—to a lesser extent—during some viral infections, such as thecommon cold.

When histamine binds to receptors on cells, it stimulates changes within the cells that lead to the release of chemicals that causesneezing,itching, and increasedmucusproduction. Antihistamines compete with histamine for cell receptors and bind to the receptors without stimulating the cells.

In addition, they prevent histamine from binding and stimulating the cells. Diphenhydramine also blocks the action of acetylcholine (anticholinergic effect) and is used as a sedative because it causes drowsiness.

Benadryl (diphenhydramine) side effects include:

• sedation,
• tiredness,
• sleepiness,
• dizziness,
• constipation,
• disturbed coordination,
• 干燥和增厚的口头和其他呼吸器y secretions, and
• urinary retention.

Diphenhydramine also may cause:

• low blood pressure,
• palpitations(abnormal heartbeats),
• increasedheartrate,
• confusion,
• nervousness,
• irritability,
• blurred vision,
• double vision,
• painful urinationordifficulty urinating,
• tremor,
• sweating,
• loss of appetite,
• erectile dysfunction, and
• nausea.

Diphenhydramine should be used with caution (if at all) in persons with narrow-angleglaucoma, prostatic hypertrophy (enlarged prostategland),hyperthyroidism,cardiovascular disease,high blood pressure(hypertension), andasthma.

Diphenhydramine doses vary depending on the formulation and have their maximal effect about one hour after it is taken.

• When used to treatinsomnia, it is prescribed at bedtime. Individuals over the age of 60 years are especially sensitive to the sedating and anticholinergic effects of diphenhydramine, and the dose should be reduced.
• A common regimen for treating adult allergic reactions is 25-50 mg every 4-6 hours not to exceed 300 mg daily.
• Insomniais treated with 50 mg taken 30 minutes before bedtime.

Diphenhydramine adds to (exaggerates) the sedating effects ofalcoholand otherdrugsthan can cause sedation.

This includes the following drug classes:

Benzodiazepines for-anxiety

• diazepam(Valium),
• lorazepam(Ativan),
• clonazepam(Klonopin),
• alprazolam(Xanax),

Narcotic pain medications and their derivatives

• oxycodone and acetaminophen(Percocet),
• hydrocodone and acetaminophen(Vicodin),
• guaifenesinwith hydromorphone (Dilaudid),
• codeine,
• propoxyphene(Darvon),

Tricyclic antidepressants

• amitriptyline(Elavil,Endep),
• imipramine(Tofranil),
• desipramine(Norpramin)

Certain antihypertensive medications

• clonidine(Catapres),
• propranolol(Inderal)

Diphenhydramine also can intensify the drying effects of other medications with anticholinergic properties (for example,dicyclomine[Bentyl] andbethanechol[Urecholine], probanthine).

• Diphenhydramine has not been adequately evaluated inpregnantwomen. It should be used only if the benefit outweighs the potential but unknown risks.
• Diphenhydramine is secreted inbreast milk. Because of the risk of stimulation andseizuresin infants, especially newborns and premature infants, antihistamines should not be used bynursingmothers.