Oxaprotiline (developmental code name C 49-802 BDA), also known as hydroxymaprotiline, is a norepinephrine reuptake inhibitor of the tetracyclic antidepressant (TeCA) family that is related to maprotiline. Though investigated as an antidepressant, it was never marketed.
Dextroprotiline acts as a
potent norepinephrine reuptake inhibitor  and  H 1 receptor antagonist, as well as a very weak  α 1-adrenergic receptor antagonist.  It has negligible  affinity for the serotonin transporter,  dopamine transporter, α, 2-adrenergic receptor  and  muscarinic acetylcholine receptors. Whether it has any  antagonistic effects on the 5-HT, 2 5-HT, or 7 D like its relative 2 receptors maprotiline is unclear.
Levoprotiline acts as a
selective H 1 receptor antagonist, with no affinity for adrenaline, dopamine, muscarinic acetylcholine, or serotonin receptors, or any of the monoamine transporters.  
Oxaprotiline is a
racemic compound composed of two isomers, R(−)- or levo- oxaprotiline ( levoprotiline; CGP-12,103-A), and S(+)- or dextro- oxaprotiline ( dextroprotiline; CGP-12,104-A). Both enantiomers are active, with the levo- form acting as an antihistamine and the dextro- form having an additional pharmacology (see above), but with both unexpectedly still retaining antidepressant effects.
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