Pharmacotherapeutic group: Antihistamines for systemic use. ATC code: R06AB03
Mechanism of action and pharmacodynamic effects
Dimetindene maleate is a competitive inhibitor of histamine at H1 receptors. At low concentrations, it stimulates histamine methyltransferase, leading to histamine inactivation. It displays strong affinity for H1 receptors and is a potent mast-cell stabiliser. It also exerts a local anaesthetic effect. It has no effect at H2 receptors. Dimetindene maleate further acts as an antagonist of bradykinin, serotonin and acetylcholine. It is a racemic mixture in which R-(-)-dimetindene has the higher H1-antihistaminic activity. It substantially reduces the increased capillary permeability associated with immediate hypersensitivity reactions.
In combination with H2 antihistamines, dimetindene maleate suppresses virtually all circulatory effects of histamine.
In a study of histamine-induced cutaneous oedema and erythema, the effect of a single 4 mg dose of dimetindene oral drops remained measurable up to 24 hours after administration.
⚠️ Warnings
As with other antihistamines, caution is advised when administering to patients with glaucoma or bladder neck obstruction (e.g. prostatic hypertrophy). As with all H1-receptor antagonists and certain H2 antihistamines, caution is required in patients with epilepsy.
Elderly patients
Elderly patients are more susceptible to anticholinergic adverse effects or to agitation and fatigue. Dimetindene should therefore be used with caution in this population. Do not use in elderly patients showing signs of confusion.
Paediatric population
Induction of excitability has been observed in young children following administration of antihistamines.
Excipients
‒ This medicinal product contains 200 mg of propylene glycol per dose (40 drops), equivalent to 100 mg/ml.
‒ This medicinal product contains less than 1 mmol sodium (23 mg) per dose, that is to say essentially "sodium-free".
‒ This medicinal product contains 2 mg of benzoic acid per dose (40 drops), equivalent to 1 mg/ml.
