diphenhydramine (Rx, OTC)Brand and Other Names:Benadryl, Benadryl Allergy Dye-Free LiquiGels, more...Children's Benadryl Allergy, Children's Triaminic Thin Strips Allergy, Alka-Seltzer Plus Allergy, Nytol, PediaCare Children's Allergy, Simply Sleep, Sominex, QlearQuil Nighttime Allergy Relief, Tranquil Nighttime Sleep Aid, Unisom SleepGels, Unisom SleepMelts, ZzzQuil

 
 
 

Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

oral liquid

  • 12.5mg/5mL (Benadryl Allergy Childrens, PediaCare Children’s Allergy, Allergy Relief Childrens)
  • 50mg/30mL (ZzzQuil)

elixir

  • 12.5 mg/5mL (Altaryl)

syrup

  • 12.5 mg/5mL (Altaryl, Quenalin, Silphen Cough)

tablet

  • 25mg (Benadryl, Nytol, Simply Sleep, Sominex, Simply Allergy, Tetra-Formula Nighttime Sleep)
  • 50mg (Aler-Dryl, Nytol Maximum Strength)

capsule

  • 25mg (Benadryl Allergy Dye-Free Allergy, Anti-Hist Allergy, Allergy Relief, Diphenhist, Geri-Dryl)
  • 50mg (Banophen, Pharbedryl)

tablet, chewable

  • 12.5mg (Benadryl Allergy Childrens)

tablet, dispersible

  • 25mg (Unisom SleepMelts)

strip

  • 12.5mg (Triaminnic Cough/Runny Nose)

injectable solution

  • 50mg/mL
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Allergic Reaction

25-50 mg PO q6-8hr; not to exceed 300 mg/day

10-50 mg (no more than 100 mg) IV/IM q4-6hr; not to exceed 400 mg/day

Insomnia

50 mg PO 30 minutes before bedtime

Cough

25-50 mg PO q4hr PRN (syrup preferred); not to exceed 150 mg/day

Motion Sickness

Treatment or prophylaxis: 25-50 mg PO q6-8 hr

Alternatively, 10-50 mg/dose for treatment; may use up to 100 mg if needed; not to exceed 400 mg

Parkinsonism

25 mg PO q8hr initially, then 50 mg PO q6hr; not to exceed 300 mg/day

Alternatively, 10-50 mg IV at a rate not to exceed 25 mg/min; not to exceed 400 mg/day; may also administer 100 mg IM required

Dosage Forms & Strengths

oral solution

  • 12.5mg/5mL (Benadryl Allergy Childrens, PediaCare Children’s Allergy, Allergy Relief Childrens)
  • 50mg/30mL (ZzzQuil)

elixir

  • 12.5 mg/5mL (Altaryl)

syrup

  • 12.5 mg/5mL (Altaryl, Quenalin, Silphen Cough)

tablet

  • 25mg (Benadryl, Nytol, Simply Sleep, Sominex, Simply Allergy, Tetra-Formula Nighttime Sleep)
  • 50mg (Aler-Dryl, Nytol Maximum Strength)

capsule

  • 25mg (Benadryl Allergy Dye-Free Allergy, Anti-Hist, Allergy Relief, Diphenhist, Geri-Dryl)
  • 50mg (Banophen, Pharbedryl)

tablet, chewable

  • 12.5mg (Benadryl Allergy Childrens)

tablet, dispersible

  • 25mg (Unisom SleepMelts)

strip

  • 12.5mg (Triaminnic Cough/Runny Nose)

injectable solution

  • 50mg/mL
more...

Allergic Reaction

2-6 years: 6.25 mg q4-6hr; not to exceed 37.5 mg/day

6-12 years: 12.5-25 mg PO q4-6hr; not to exceed 150 mg/day

>12 years: 25-50 mg PO q4-6hr; not to exceed 300 mg/day

Occasional Insomnia

< 12 years (off-label): 1 mg/kg; not to exceed 50 mg; 30 min before bedtime

>12 years: 50 mg PO 30 minutes before bedtime

Cough

<12 years: Safety and efficacy not established

>12 years: 25-50 mg PO q4-6hr; not to exceed 300 mg/day

Motion Sickness

Administer 30 min before motion

12.5-25 mg PO q6-8hr or 150 mg/m² ; not to exceed 300 mg/day

Allergic Reaction

25 mg PO/IV/IM q8-12hr; use only for emergency allergic reactions at smallest effective dose

Nonanticholinergic antihistamines should be considered first for treatment of allergic reaction (Beers criteria); use of diphenhydramine in acute treatment of severe allergic reaction may be appropriate

Dystonic Reaction

50 mg IV/IM; may be repeated in 20-30 minutes if necessary

Cough

25 mg PO q8-12hr; avoid in elderly if possible

Motion Sickness

25 mg PO/IV/IM q8-12hr 

Dosing Modifications

Advanced age is associated with reduced clearance of drug and greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity; if used, consider lower doses

In patients with parkinsonism who are unable to tolerate more potent agents, use at lowest effective dose

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Interactions

Interaction Checker

diphenhydramine and

No Results

     
     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            Frequency Not Defined

            Sedation

            Confusion

            Anticholinergic effects

            May decrease cognitive function in geriatric patients

            Xerostomia

            Dry nasal mucosa

            Pharyngeal dryness

            Thick bronchial sputum

            Agranulocytosis

            Hemolytic anemia

            Thrombocytopenia

            Convulsions

            Tachycardia

            Hypotension

            Nervousness

            Restlessness

            Blurred vision

            Palpitations

            Constipation

            Vertigo

            Menstrual irregularities

            Euphoria

            Anorexia

            Urinary retention

            Neuritis

            Diplopia

            Tinnitus

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            Warnings

            Contraindications

            Documented hypersensitivity

            Lower respiratory tract disease, such as acute asthma (controversial)

            Premature infants or neonates

            Nursing mothers

            Use as local anesthetic

            To make child <6 years sleep, when used for self-medication

            Cautions

            May cause CNS depression, which can impair driving or operating heavy machinery

            May potentiate effects of sedatives such as alcohol

            Use caution in patients with angle-closure glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, thyroid dysfunction

            Elderly patients: Considered high-risk medication for this age group because it may increase risk of falls and has high incidence of anticholinergic effects; may exacerbate existing lower urinary tract conditions or benign prostatic hyperplasia; use in special situations may be appropriate; not recommended for treatment of insomnia, because tolerance develops and risk of anticholinergic effects increases

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            Pregnancy & Lactation

            Pregnancy category: B

            Lactation: Drug enters breast milk; contraindicated

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Histamine H1-receptor antagonist of effector cells in respiratory tract, blood vessels, and GI smooth muscle

            Moderate to high anticholinergic and antiemetic properties

            Absorption

            Bioavailability: PO, 42-62% (drug is well absorbed but undergoes first-pass metabolism)

            Onset: 15-30 min 

            Duration: ≤12 hr (histamine-induced flare suppression); ≤10 hr (histamine-induced wheal suppression)

            Peak serum time: 2 hr (PO)

            Distribution

            Protein bound: 98.5%

            Vd: 22 L/kg (Children); 17 L/kg (adults); 14 L/kg (elderly)

            Metabolism

            Metabolized by liver (first-pass)

            Elimination

            Half-life: 5 hr (children); 9 hr (adults); 13.5 hr (elderly)

            Excretion: Urine (50-75%), mainly as metabolites

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            Administration

            IV Incompatibilities

            Additive: Amobarbital, amphotericin B, dexamethasone, sodium phosphate with lorazepam and metoclopramide, iodipamide meglumine, phenytoin, phenobarbital, thiopental

            Syringe: Diatrizoate meglumine 52% and diatrizoate sodium 8%, diatrizoate sodium, haloperidol, iodipamide meglumine, ioxaglate meglumine 39.3% and ioxaglate sodium 19.6%, pentobarbital, thiopental

            Y-site: Allopurinol, amphotericin B cholesteryl sulfate, cefepime, foscarnet, furosemide, phenytoin

            IV Administration

            pH: 5-6

            Infuse at rate no higher than 25 mg/min

            Check patency of IV and monitor for irritation

            Storage

            Store at room temperature of 15-30°C (59-86°F); protect from freezing and light

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            Formulary

            FormularyPatient Discounts

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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
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