Diphenhydramine Hydrochloride
Generic Details
Generic Name
Diphenhydramine Hydrochloride
Other Names
- Benedryl
Drug Class
- Antihistamine
- Antiemetic
- Sedative
Chemical Formula
C17H21NO
Molecular Weight
255.36 g/mol
Mechanism of Action
- Blocks histamine receptors
- Antagonizes acetylcholine
Indications
- Allergic reactions
- Insomnia
- Motion sickness
- Common cold symptoms
Common Dosage Forms
- Tablet
- Capsule
- Liquid
- Topical cream
Typical Dosage
- 25-50 mg every 4-6 hours as needed
Pediatric Dosage
- 2-12 years: 12.5-25 mg every 4-6 hours as needed
Geriatric Dosage
- Dosage adjustments may be needed due to decreased clearance
Side Effects
- Drowsiness
- Dry mouth
- Blurred vision
- Constipation
- Urinary retention
Contraindications
- Narrow-angle glaucoma
- Severe liver disease
- Hypersensitivity to diphenhydramine
Pregnancy Category
- Category B - No teratogenic effects observed in animal studies
Lactation Safety
- Excreted into breast milk, caution advised
Drug Interactions
- Alcohol
- Sedatives
- Other anticholinergic drugs
Overdose Symptoms
- Severe drowsiness
- Confusion
- Seizures
- Coma
Antidote for Overdose
- Administer activated charcoal
- Physostigmine in severe cases
Storage Conditions
- Store at room temperature away from moisture and light
Pharmacokinetics
- Absorption: Well absorbed orally
- Distribution: Crosses the blood-brain barrier and placenta, enters breast milk
- Metabolism: Hepatic metabolism via cytochrome P450 enzymes
- Excretion: Primarily renal excretion of metabolites
Precautions
- Use caution in elderly patients
- Avoid in patients with asthma or COPD due to anticholinergic effects
Warnings
- May cause drowsiness, avoid driving or operating machinery until effects are known
Others
- May be used as a sleep aid due to sedative effects