| Indication | Used to prevent and relieve allergic conditions which cause pruritus (itching) and urticaria (some allergic skin reactions). |
| Pharmacodynamics | Trimeprazine (also known as Alimemazine) is a tricyclic antihistamine, similar in structure to the phenothiazine antipsychotics, but differing in the ring-substitution and chain characteristics. Trimeprazine is in the same class of drugs as chlorpromazine (Thorazine) and trifluoperazine (Stelazine); however, unlike the other drugs in this class, trimeprazine is not used clinically as an anti-psychotic. It acts as an anti-histamine, a sedative, and an anti-emetic (anti-nausea). Trimeprazine is used principally as an anti-emetic, to prevent motion sickness or as an anti-histamine in combination with other medications in cough and cold preparations. Tricyclic antihistamines are also structurally-related to the tricyclic antidepressants, explaining the antihistaminergic adverse effects of these two drug classes and also the poor tolerability profile of tricyclic H1-antihistamines. |
| Mechanism of action | Trimeprazine competes with free histamine for binding at HA-receptor sites. This antagonizes the effects of histamine on HA-receptors, leading to a reduction of the negative symptoms brought on by histamine HA-receptor binding. |
| Absorption | Well absorbed in the digestive tract. |
| Volume of distribution | Not Available |
| Protein binding | Not Available |
| Metabolism | Hepatic |
| Route of elimination | Not Available |
| Half life | Not Available |
| Clearance | Not Available |
| Toxicity | Symptoms of overdose clumsiness or unsteadiness, seizures, severe drowsiness, flushing or redness of face, hallucinations, muscle spasms (especially of neck and back), restlessness, shortness of breath, shuffling walk, tic-like (jerky) movements of head and face, trembling and shaking of hands, and insomnia. |