Diferencia entre revisiones de «Diphenhydramine»
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Revisión actual - 21:55 20 mar 2026
General
- Type: Antihistamines / H1 blocker
- Dosage Forms: Oral, IM, IV
- Common Trade Names: Benadryl
Adult Dosing
- Allergic reaction
- Oral: 25-50mg q4-8h, max 300mg/day
- IM/IV: 10-50mg/dose
- Parkinsonian symptoms
- Oral: 25-50mg tid-QID
- IM/IV: 10-50mg/dose
- Insomnia: 50mg PO qhs
- Injectable 1% diphenhydramine (10 mg/mL) can be used as a local anesthestic alternative to ester/amide anesthetics[1]
- Sodium channel blocker mechanism
- 1-2 mL of 1% diphenhydramine at a time, to not exceed excessive sedation dose
- Typical vial is 50 mg/mL, so to make 10 mg/mL:
- 10 mL NS removed from 50 mL vial
- Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
- Sedation is dose related and is similar to what would be expected for IM doses
- Relative contraindications are the same for IM diphenhydramine administration
Pediatric Dosing
- Allergic reaction
- Oral/IM/IV: 5mg/kg/day divided q6-8h (1.25-1.67mg/kg/dose)
- Alternate PO dosing
- 2-6 yo: 6.25mg q4-6h
- 6-12 yo: 12-25mg q4-6h
- >12 yo: Adult dosing
Special Populations
- Pregnancy Rating: B
- Lactation Risk: Enters breast milk
- Renal Dosing: n/a
- Hepatic Dosing: n/a
Contraindications
- Allergy to class/drug
Adverse Reactions
Serious
- Anticholinergic toxicity
- CNS depression
- Cardiac arrthymias (Sodium channel blockade)
- Seizures
Common
- Sedation
- Opsoclonus - conjugate irregular and nonrhythmical jerking movements of the eyes was reported in a 20-year-old woman who had ingested 5 grams[2]
Pharmacology
- Half-life: Children 5 hours, Adults 9 hours, Elderly 13.5 hours
- Metabolism: Hepatic
- Excretion: Urine
- Mechanism of Action: Antihistamines / H1 blocker
Indications by Condition
The following table is automatically generated from disease/condition pages across WikEM.
| Indication | Dose | Context | Route | Population |
|---|---|---|---|---|
| Acute allergic reaction | 50mg | H1 antagonist | IV/IM/PO | Adult |
| Akathisia | 50mg PO/IM/IV | Anticholinergic, first-line | PO/IM/IV | Adult |
| Angioedema | 50 mg IV | Antihistamine (allergic angioedema) | IV | Adult |
| Antipsychotic toxicity | 25-50mg IV/IM | Dystonic reaction | IV/IM | Adult |
| Cannabinoid hyperemesis syndrome | 50mg IV | Adjunct with haloperidol | IV | Adult |
| Dystonic reaction | 25-50mg IV over 2 min | Anticholinergic, first-line | IV | Adult |
| Extrapyramidal reaction | 25-50mg PO or IV | Anticholinergic for acute dystonia/akathisia | PO/IV | Adult |
| Headache | 25-50 mg IV | Adjunct to prevent akathisia | IV | Adult |
| Migraine headache | 12.5-25 mg IV | Adjunct to prevent akathisia/EPS | IV | Adult |
| Migraine headache | 25-50 mg IV | Adjunct to prevent akathisia | IV | Adult |
| Vertigo | 25-50 mg q4hr | Antihistamine (vestibular suppressant) | IV/IM/PO | Adult |
See Also
References
- ↑ Pavlidakey PG et al. Diphenhydramine as an Alternative Local Anesthetic Agent. J Clin Aesthet Dermatol. 2009 Oct; 2(10): 37–40.
- ↑ NEJM. http://www.nejm.org/action/showMediaPlayer?doi=10.1056%2FNEJMicm1002035&aid=NEJMicm1002035_attach_1&area=&