Prediction of catalepsies induced by amiodarone, aprindine and procaine: similarity in conformation of diethylaminoethyl side chain.

Recently, clinical cases of parkinsonism due to antiarrhythmics drugs amiodarone and aprindine and a local anesthetic drug procaine have been reported. We performed both in vivo and in vitro experiments to quantitatively predict the intensity of catalepsy by these drugs and haloperidol in mice. Haloperidol showed the most potent relative intensity of catalepsy, followed by aprindine, metoclopramide, tiapride, amiodarone and procaine, in that order. In vivo dopamine D1 and D2 receptor occupancies of the six drugs to the striatum were observed. In vitro binding affinity (Ki) of these drugs to the D1 and D2 receptors in the striatum synaptic membrane was within the range of 60 nM to 706 microM, 0.5 nM to 75 microM and 860 nM to 115 microM, respectively. A good correlation between the relative intensity of drug-induced catalepsy and the Ki values for the dopamine D1 and D2 receptors was obtained (r =.911 and r =.896, respectively; P <.05). The partial tertiary structure of the tested drugs was well superimposed on that of haloperidol. In conclusion, these drug-induced catalepsies were due to the blockade of the D1 and D2 receptors, which was related to the analogous tertiary structures (diethylaminoethyl side chain).