Selective M2 receptor antagonist
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Tripitramine, or tripitamine, is an antimuscarinic drug which was never marketed.
Pharmacology.
The drug is a selective antagonist of the muscarinic acetylcholine M2 receptor. Its affinities (Ki) for the muscarinic acetylcholine receptors are 0.27nM for the M2 receptor, 1.58nM for the M1 receptor (5.9-fold less than for M2), 6.41nM for the M4 receptor (24-fold less than for M2), 33.87nM for the M5 receptor (125-fold less than for M2), and 38.25nM for the M3 receptor (142-fold less than for M2). Tripitramine has been found to be cardioselective and to increase heart rate in animals.
Chemistry.
Structurally, it consists of three pirenzepine- or AQ-RA 741-like tricyclic (more specifically pyridobenzodiazepine) moieties bound together by a long amine-containing hydrocarbon chain similar to the one found within methoctramine (a modestly M2-selective antimuscarinic agent). Related compounds with analogous structural designs include dipitramine, spirotramine, caproctamine, and benextramine, among others.
History.
Tripitramine was first described in the scientific literature by 1993. It was developed in efforts to discover more highly selective M2 receptor antagonists than methoctramine.
References.
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