General Articles

Acetaminophen and diphenhydramine

MEDICATION SAFETY ISSUES
Sound-alike/look-alike issues:
Excedrin® may be confused with Dexatrim®, Dexedrine®
Percogesic® may be confused with paregoric, Percodan®
Tylenol® may be confused with atenolol, timolol, Tuinal®, Tylox®
Tylenol® PM may be confused with Tylenol®

Duplicate therapy issues: This product contains acetaminophen, which may be a component of other combination products. Do not exceed the maximum recommended daily dose of acetaminophen.

U.S. BRAND NAMES — Excedrin PM® [OTC]; Goody’s PM® [OTC]; Legatrin PM® [OTC]; Mapap PM [OTC]; Percogesic® Extra Strength [OTC]; Tylenol® PM [OTC]; Tylenol® Severe Allergy [OTC]

PHARMACOLOGIC CATEGORY
Analgesic, Miscellaneous

DOSING: ADULTS — Insomnia and pain: Oral: Adults: 50 mg of diphenhydramine HCl (76 mg diphenhydramine citrate) at bedtime or as directed by physician; do not exceed recommended dosage

DOSING: PEDIATRIC — Not for use in children <12 years of age. DOSING: ELDERLY — Refer to adult dosing. DOSING: HEPATIC IMPAIRMENT — Use with caution. Limited, low-dose therapy is usually well tolerated in hepatic disease/cirrhosis; however, cases of hepatotoxicity at daily acetaminophen dosages <4 g/day have been reported. Avoid chronic use in hepatic impairment. DOSAGE FORMS — Excipient information presented when available (limited, particularly for generics); consult specific product labeling. Caplet, oral: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg
Excedrin PM®: Acetaminophen 500 mg and diphenhydramine citrate 38 mg
Legatrin PM®: Acetaminophen 500 mg and diphenhydramine hydrochloride 50 mg
Mapap PM: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg
Percogesic® Extra Strength: Acetaminophen 500 mg and diphenhydramine hydrochloride 12.5 mg
Tylenol® PM: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg
Tylenol® Severe Allergy: Acetaminophen 500 mg and diphenhydramine hydrochloride 12.5 mg

Gelcap, rapid release, oral:
Tylenol® PM: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg

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Geltab, oral: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg
Excedrin® PM: Acetaminophen 500 mg and diphenhydramine citrate 38 mg
Tylenol® PM: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg

Liquid, oral:
Tylenol® PM: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg per 15 mL (240 mL) [contains sodium benzoate; vanilla flavor]

Powder for solution, oral:
Goody’s PM®: Acetaminophen 500 mg and diphenhydramine citrate 38 mg [contains potassium 41.9 mg and sodium 3.15 mg per powder]

Tablet, oral: Acetaminophen 500 mg and diphenhydramine hydrochloride 25 mg
Excedrin® PM: Acetaminophen 500 mg and diphenhydramine citrate 38 mg

DOSAGE FORMS: CONCISE
Caplet, oral: Acetaminophen 500 mg and diphenhydramine 25 mg
Excedrin PM® [OTC]: Acetaminophen 500 mg and diphenhydramine 38 mg
Legatrin PM® [OTC]: Acetaminophen 500 mg and diphenhydramine 50 mg
Mapap PM [OTC], Tylenol® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 25 mg
Percogesic® Extra Strength [OTC]: Acetaminophen 500 mg and diphenhydramine 12.5 mg
Tylenol® Severe Allergy [OTC]: Acetaminophen 500 mg and diphenhydramine 12.5 mg

Gelcap, rapid release, oral:
Tylenol® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 25 mg

Geltab, oral: Acetaminophen 500 mg and diphenhydramine 25 mg
Excedrin® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 38 mg
Tylenol® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 25 mg

Liquid, oral:
Tylenol® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 25 mg per 15 mL

Powder for solution, oral:
Goody’s PM® [OTC]: Acetaminophen 500 mg and diphenhydramine 38 mg

Tablet, oral: Acetaminophen 500 mg and diphenhydramine 25 mg
Excedrin® PM [OTC]: Acetaminophen 500 mg and diphenhydramine 38 mg

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GENERIC EQUIVALENT AVAILABLE — Yes: Excludes gelcap, powder, and liquid

USE — Aid in the relief of insomnia accompanied by minor pain

ADVERSE REACTIONS SIGNIFICANT — See individual agents.

METABOLISM / TRANSPORT EFFECTS
Acetaminophen: Substrate (minor) of CYP1A2, 2A6, 2C9, 2D6, 2E1, 3A4; Inhibits CYP3A4 (weak)

Diphenhydramine: Inhibits CYP2D6 (moderate)

DRUG INTERACTIONS
Acetylcholinesterase Inhibitors (Central): Anticholinergics may diminish the therapeutic effect of Acetylcholinesterase Inhibitors (Central). Acetylcholinesterase Inhibitors (Central) may diminish the therapeutic effect of Anticholinergics. If the anticholinergic action is a side effect of the agent, the result may be beneficial. Risk C: Monitor therapy

Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy

Amphetamines: May diminish the sedative effect of Antihistamines. Risk C: Monitor therapy

Anticholinergics: May enhance the adverse/toxic effect of other Anticholinergics. Exceptions: Paliperidone. Risk C: Monitor therapy

Anticonvulsants (Hydantoin): May increase the metabolism of Acetaminophen. This may 1) diminish the effect of acetaminophen; and 2) increase the risk of liver damage. Risk C: Monitor therapy

Barbiturates: May increase the metabolism of Acetaminophen. This may 1) diminish the effect of acetaminophen; and 2) increase the risk of liver damage. Risk C: Monitor therapy

Betahistine: Antihistamines may diminish the therapeutic effect of Betahistine. Risk C: Monitor therapy

CarBAMazepine: May increase the metabolism of Acetaminophen. This may 1) diminish the effect of acetaminophen; and 2) increase the risk of liver damage. Risk C: Monitor therapy

Cholestyramine Resin: May decrease the absorption of Acetaminophen. Effect is minimal if cholestyramine is administered 1 hour after acetaminophen. Risk D: Consider therapy modification

CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy

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Codeine: CYP2D6 Inhibitors (Moderate) may diminish the therapeutic effect of Codeine. These CYP2D6 inhibitors may prevent the metabolic conversion of codeine to its active metabolite morphine. Risk C: Monitor therapy

CYP2D6 Substrates: CYP2D6 Inhibitors (Moderate) may decrease the metabolism of CYP2D6 Substrates. Exceptions: Tamoxifen. Risk C: Monitor therapy

Fesoterodine: CYP2D6 Inhibitors may increase serum concentrations of the active metabolite(s) of Fesoterodine. Risk C: Monitor therapy

Imatinib: May increase the serum concentration of Acetaminophen. Risk D: Consider therapy modification

Isoniazid: May enhance the adverse/toxic effect of Acetaminophen. Risk C: Monitor therapy

Nebivolol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Nebivolol. Risk C: Monitor therapy

Peginterferon Alfa-2b: May decrease the serum concentration of CYP2D6 Substrates. Risk C: Monitor therapy

Pramlintide: May enhance the anticholinergic effect of Anticholinergics. These effects are specific to the GI tract. Risk D: Consider therapy modification

Tamoxifen: CYP2D6 Inhibitors (Moderate) may decrease the metabolism of Tamoxifen. Specifically, CYP2D6 inhibitors may decrease the formation of highly potent active metabolites. Risk D: Consider therapy modification

TraMADol: CYP2D6 Inhibitors (Moderate) may diminish the therapeutic effect of TraMADol. These CYP2D6 inhibitors may prevent the metabolic conversion of tramadol to its active metabolite that accounts for much of its opioid-like effects. Risk C: Monitor therapy

Vitamin K Antagonists (eg, warfarin): Acetaminophen may enhance the anticoagulant effect of Vitamin

K Antagonists. Most likely with daily acetaminophen doses >1.3 g for >1 week. Risk C: Monitor therapy

ETHANOL / NUTRITION / HERB INTERACTIONS — Ethanol: Excessive intake of ethanol may increase the risk of acetaminophen-induced hepatotoxicity. Avoid ethanol or limit to <3 drinks/day. PHARMACODYNAMICS / KINETICS — See individual agents.