The influence of verapamil and nifedipine on neuromuscular blocking agents
Fukushima, K.; Aoki, T.; Ishikawa, J.
Masui. Japanese Journal of Anesthesiology 33(12): 1346-1350
1984
ISSN/ISBN: 0021-4892 PMID: 6530737 Document Number: 236150
Ca blocking drugs are becoming popular in the treatment of cardiovascular diseases. Ca2+ is essential for neuromuscular transmission and muscle contraction. The purpose of the present study was to investigate and get some information on the interaction of Ca2+ inhibitors with muscle relaxants. The experiments were carried out on the rat phrenic nerve-hemidiaphragm preparation. The preparation was stimulated indirectly with a square wave pulse of 0.1 Hz and 1.0 ms duration supramaximally. The cumulative dose response curves of dTc were administered. Verapamil and nifedipine themselves had no effect on twitch tension, but they potentiated the effect of the neuromuscular block of dTc, PCB and SCC significantly. After washout of the preparation, twitch tension recovered more markedly in the absence than in the presence of Ca2+ inhibitors. The antagonistic effect of neostigmine and 4-AP on the depressed twitch tension induced with Ca2+ inhibitors was poor compared with the blockade in the absence of Ca2+ inhibitors. The patients with prolonged use of clinical doses of verapamil and nifedipine may have accumulated them at the neuromuscular junction and they will potentiate the effect of muscle relaxants.