Chemical formula: C₁₇H₂₀N₂S Molecular mass: 284.419 g/mol PubChem compound: 4927
Potent, long acting, antihistamine with additional anti-emetic central sedative and anti-cholinergic properties.
Promethazine hydrochloride is readily absorbed from the gastrointestinal tract, but undergoes extensive first pass metabolism in the liver. With only 25% of the oral dose reaching the systemic circulation unchanged. After oral therapy therapeutic effects are identifiable at 15-30 minutes and peak plasma concentrations at 2 to 3 hours. Estimates of terminal half-life in blood plasma have been quoted as 4-6 hours. It is extensively plasma protein bound. It is eliminated mainly as metabolites, predominantly by the faecal (via biliary) route, with <1% of the parent compound and CA 10% as the sulfoxide metabolite being excreted in the urine over a 72 hour period.
It is distributed widely in the body. It enters the brain and crosses the placenta. Phenothiazines pass into the milk at low concentrations.
None stated.
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