SOMMEIL CAPSULES
DIPHENHYDERAMINE HCL 25MG
What it does
Diphenhydramine is an antihistamine used to relieve allergy symptoms and aid sleep.
Commonly used for: allergies, hay fever, insomnia, motion sickness
Read more in plain English ↓Plain-language summary for general understanding - not medical advice. Always follow your pharmacist/doctor.
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Sourcing - Kenya onlyRegistration & product details
Source: Food and Drugs Authority · fetched 2026-04-18 08:33:03 · updated 2026-10-20 04:00:12
About this medicine
Diphenhydramine is an antihistamine used to relieve allergy symptoms and aid sleep.
What it treats
- allergies
- hay fever
- insomnia
- motion sickness
How it works
It blocks the action of histamine, a substance in the body that causes allergic symptoms.
Who it's for
It is suitable for adults and children over a certain age, but always check with a healthcare provider before use.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: diphenhyderamine
Diphenhydramine is an antihistamine of the ethanolamine class, primarily used to relieve symptoms of allergy, hay fever, and the common cold. It is effective in treating symptoms such as runny nose, sneezing, itching, and watery eyes. Additionally, diphenhydramine is commonly used as a short-term treatment for insomnia and to prevent or treat nausea and vomiting associated with motion sickness.
Indications
- Allergic rhinitis
- Allergic conjunctivitis
- Urticaria
- Insomnia
- Motion sickness
- Common cold symptoms
Dosage
Children: Refer to the BNF for Children for specific dosing information in children, as doses are based on age and weight.
Adults: Refer to the BNF for specific dosing information, as doses may vary for individual conditions.
Mechanism of action
Diphenhydramine works as an antagonist of the H1 histamine receptor, blocking the effects of endogenous histamine. This action reduces capillary permeability, vascular smooth muscle contraction, and effects on the central nervous system, leading to sedation and relief from allergic symptoms.
Pharmacodynamics
Diphenhydramine exhibits sedative properties due to its ability to cross the blood-brain barrier and antagonize H1 receptors in the central nervous system. The anticholinergic effects contribute to its ability to reduce secretions, making it helpful in treating respiratory tract symptoms. Its effects on the central nervous system can induce drowsiness, making it useful for sleep induction.
Pharmacokinetics
Diphenhydramine is well absorbed after oral administration, with peak plasma concentrations occurring within 1 to 4 hours. It is extensively metabolized in the liver, primarily by cytochrome P450 enzymes, and has a half-life of approximately 4 to 8 hours. Diphenhydramine is excreted mainly in the urine as metabolites, with only a small percentage as unchanged drug.
Contra-indications
- Hypersensitivity to diphenhydramine or any of its excipients
- Severe asthma
- Narrow-angle glaucoma
- Prostatic hypertrophy
- Pyloroduodenal obstruction
Adverse effects
- Drowsiness
- Dizziness
- Dry mouth
- Constipation
- Blurred vision
- Urinary retention
Interactions
- CNS depressants (e.g., alcohol, benzodiazepines) may enhance sedative effects
- MAO inhibitors may prolong and intensify anticholinergic effects
- Anticholinergic drugs may increase side effects
- Use with caution with other antihistamines
Precautions
- Use with caution in elderly patients due to increased sensitivity to sedative effects
- Patients with a history of seizures or increased intraocular pressure
- Caution in patients with cardiovascular disease due to potential tachycardia
Pregnancy
Diphenhydramine is classified as category B. Animal reproduction studies have not shown a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women. Use only if clearly needed.
Breast-feeding
Diphenhydramine is excreted in breast milk. Caution is advised when administering to nursing mothers due to potential sedative effects on the infant.
Storage
Store at room temperature, away from moisture and heat. Keep out of reach of children.
Formulations
- Oral tablets
- Oral liquid
- Injectable solution
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.