In clinical trials oxyphencyclimine hydrochloride (5 mg) was prescribed daily, one tablet three times a day.

[3H]NMS binding to M4 receptor was measured at 25°C in a total volume of 1.2 ml using the following incubation buffer: 50 mM sodium phosphate (pH 7.4) enriched with 2 mM MgCI2, 1% bovine serum albumin (except when indicated) and the indicated tracer and drug concentrations. In binding experiments on rat striatum ho-mogenates, the tracer concentration was 0.25 nM and the protein concentration 30-40 ug per assay (about 50 pM binding sites). Under equilibrium conditions (2 h incubation at 25°C) [3H]NMS labelled M,. M, and M4 sites in this brain region. To analyze tracer binding to M4 sites only, striatum homogenates were preincubated for 2 h at 25°C to allow equilibrium binding, then induced tracer dissociation by adding 1 uM atropine. [3H]NMS dissociated from its binding sites after 35 min of isotopic dilution, the residual binding being about 30% of initial binding. R-enantiomer of Oxyphencyclimine displaced binding of [3H]NMS to M4 receptors with pKi of 9.2, whereas binding of its S-enantiomer was less potent.