Effect of some antiarrhythmics on [3H]clonidine binding to alpha 2-adrenergic receptors

The effects of the antiarrhythmics quinidine, propranolol, procainamide and lidocaine were determined on the specific binding of [3H]clonidine to the alpha 2-adrenergic receptor. Quinidine is effective in decreasing specific [3H]clonidine binding to the alpha 2 receptor within the range of therapeutic blood levels (Ki = 6 x 10 (-8) M). The effectiveness of all compounds tested, with the exception of quinidine and procainamide, correlate with the membrane/buffer partition coefficient, suggesting a relationship with the local anesthetic activity.