indication

For the relief of the symptoms of upper respiratory mucosal congestion in perennial and allergic rhinitis, and for the relief of nasal congestion and eustachian t.b. congestion.

pharmacology

Azatadine is an antihistamine, related to cyproheptadine, with anti-serotonin, anticholinergic (drying), and sedative effects. Azatadine is in the same class of drugs as chlorpromazine (Thorazine) and trifluoperazine (Stelazine); however, unlike the other drugs in this class, azatadine is not used clinically as an anti-psychotic. Antihistamines antagonize the vasodilator effect of endogenously released histamine, especially in small vessels, and mitigate the effect of histamine which results in increased capillary permeability and edema formation. As consequences of these actions, antihistamines antagonize the physiological manifestations of histamine release in the nose following antigen-antibody interaction, such as congestion related to vascular engorgement, mucosal edema, and profuse, watery secretion, and irritation and sneezing resulting from histamine action on afferent nerve terminals.

mechanism of action

Antihistamines such as azatadine appear to compete with histamine for histamine H1- receptor sites on effector cells. The antihistamines antagonize those pharmacological effects of histamine which are mediated through activation of H1- receptor sites and thereby reduce the intensity of allergic reactions and tissue injury response involving histamine release.

toxicity

The oral LD₅₀ in mature rats and mice was greater than 1700 mg/kg and 600 mg/kg, respectively. Symptoms of overdose include 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.

biotransformation

Hepatic.

absorption

Well absorbed after oral administration.

drug interactions

Donepezil: Possible antagonism of action

Galantamine: Possible antagonism of action

Rivastigmine: Possible antagonism of action