Clindamycin and lincomycin alter miniature endplate current decay.

Antibiotic-induced muscle paralysis has frequently been found in both experimental animals and man with three distinct classes of antibiotic: (1) streptomycin and related aminoglycoside compounds, (2) polymyxins and (3) tetracyclines. Recently lincomycin and its chemical congener, clindamycin, have been reported to produce muscle paralysis which has different characteristics from those seen with other classes of antibiotic. Although closely related in chemical structure, lincomycin and clindamycin also seem to produce muscle paralysis by different mechanisms. Clindamycin is considered to exert a direct depressant action on muscle contractility whereas the action of lincomycin is considered to be primarily a depression of neuromuscular transmission. We report here that each of these antibiotics had a significant but different influence on endplate channel behaviour. Clindamycin increased the rate of miniature endplate current (m.e.p.c.) decay and reduced its voltage sensitivity without altering its exponential nature. Lincomycin split m.e.p.c. decay into an initial rapid phase followed by a prolonged phase.