What it does
Dimethendene is an antihistamine that helps relieve allergy symptoms.
Commonly used for: allergic reactions, hay fever (allergic rhinitis), itching, rash
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Source: Pharmacy and Medicines Regulatory Authority · fetched 2026-04-21 17:37:39 · updated 2026-09-19 04:30:22
About this medicine
Dimethendene is an antihistamine that helps relieve allergy symptoms.
What it treats
- allergic reactions
- hay fever (allergic rhinitis)
- itching
- rash
How it works
It blocks the action of histamine, a substance in the body that causes allergic symptoms.
Who it's for
This medicine is suitable for adults and children who are experiencing allergy-related symptoms.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: dimethendene
Dimethendene is an antihistamine belonging to the first generation of H1 receptor antagonists. It is primarily used for the treatment of allergic conditions, including hay fever, allergic rhinitis, and urticaria. Due to its sedative effects, it is also used to alleviate symptoms of motion sickness and to induce sedation prior to surgical procedures.
Indications
- Allergic rhinitis
- Urticaria (hives)
- Motion sickness
- Sedation prior to surgical procedures
Dosage
Children: Refer to the BNF for Children for specific dosing information.
Adults: Refer to the BNF for specific dosing information.
Mechanism of action
Dimethendene exerts its effects by competitively inhibiting the action of histamine at the H1 receptor sites. This leads to a reduction in the physiological effects of histamine, such as vasodilation and increased permeability of blood vessels, which are responsible for allergic symptoms. Additionally, dimethendene has anticholinergic properties, which contribute to its effects in treating motion sickness.
Pharmacodynamics
As a first-generation antihistamine, dimethendene not only blocks H1 receptors but also crosses the blood-brain barrier, leading to central nervous system effects. These effects include sedation and potential impairment of cognitive function. The drug's efficacy in alleviating allergic symptoms is usually observed within 1 hour of administration, with a duration of action that can last several hours.
Pharmacokinetics
Dimethendene is absorbed rapidly from the gastrointestinal tract, with peak plasma concentrations occurring within 1 to 2 hours after oral administration. The drug is extensively metabolized in the liver, primarily through cytochrome P450 enzymes. Its metabolites are excreted via the urine. The elimination half-life of dimethendene is generally around 4 to 8 hours, but this can vary based on individual patient factors.
Contra-indications
- Hypersensitivity to dimethendene or any components of the formulation
- Severe liver impairment
- Closed-angle glaucoma
- Prostatic hypertrophy
Adverse effects
- Drowsiness
- Dry mouth
- Dizziness
- Nausea
- Vomiting
- Constipation
- Blurred vision
- Urinary retention
Interactions
- CNS depressants (e.g., alcohol, benzodiazepines) may enhance sedative effects
- Anticholinergic drugs may increase the risk of adverse effects
- MAO inhibitors may intensify the effects of antihistamines
Precautions
- Caution in patients with asthma or other respiratory conditions due to potential drying effects on respiratory secretions
- Use with caution in the elderly due to increased susceptibility to side effects
- Monitor for sedation in patients operating machinery or driving
Pregnancy
The safety of dimethendene in pregnancy has not been established. It should only be used if the benefits outweigh the risks.
Breast-feeding
It is not known whether dimethendene is excreted in human milk. Caution is advised when administering to nursing mothers.
Storage
Store at room temperature, away from moisture and heat. Keep out of reach of children.
Formulations
- Tablets
- Syrup
- 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.