title: Neuromuscular and cardiovascular depression produced by prolonged exposure to Polymyxin B.
abstract: It has been reported previously that in cats pre-treatment for 24 to 48 hours with neomycin sulphate resulted in a change in the pattern of neuromuscular block subsequently produced with this antibiotic. The unique characteristics of neomycin-induced neuromuscular block observed during acute exposure gave way to a pattern of block usually observed with tubocurarine. In a similar experiment on six cats we have demonstrated that with polymyxin B prolonged exposure did not result in a comparable time-dependent change in the nature of the neuromuscular block it produced, in terms of train-of-four, tetanic, and post-tetanic behaviour of the neurally-elicited muscle response. The differing characteristics of neuromuscular block seen with various antibiotics, e.g. the aminoglycoside neomycin as opposed to the polypeptide polymyxin B, during acute and sub-chronic exposure is stressed. Previously observed ability of 4 aminopyridine 0.6 mg/kg to reverse the neuromuscular and cardiovascular depression during acute exposure to polymyxin B persisted in prolonged exposure.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003864:Depression, Chemical; D005260:Female; D007022:Hypotension / Q000139:chemically induced; D008297:Male; D009469:Neuromuscular Junction / Q000187:drug effects*; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*
chemical_list: D011113:Polymyxins; D011112:Polymyxin B