CERTAIN ANTIBIOTIC, ESPECIALLY AMINOGLYCOSIDES, CLINDAMYCIN, COLISTIN AND OTHERS HAVE A NEUROMUSCULAR BLOCKING ACTION, MAY ANTAGONISE ITS EFFECT. SOME GENERAL ANESTHETICS, ANTIARRHYTHMIC AGENT AND BETABLOCKERS MAY REDUCE THE EFFECTIVENESS OF TREATMENT WITH PARASYMPATHOMIMETICS IN MYASTHENIA.IN PTS RECIEVING BETABLOCKERS IT HAS PROLONG BRADYCARDIA EFFECT. IT PROLONGS THE EFFECTOF SUXAMETHONIUM.