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52 patients selected at random were assigned to four groups according to the surgery and muscle relaxant used: vecuronium (group A) and suxamethonium (group B) in ENT, vecuronium (group C) and suxamethonium (group D) for laser surgery. The first dose of vecuronium was 0.05 mg X kg-1, followed by repeat doses of 0.0125 mg X kg-1; suxamethonium was first given in a dose of 1 mg X kg-1, this being followed by a drip of 3 mg X kg-1. The anaesthetic protocol was the same for all groups. The results showed a shorter onset of action with suxamethonium (group A: 210 +/- 30 s, group B: 75 +/- 15 s, group C: 200 +/- 50 s, group D: 80 +/- 20 s) and a similar duration of action for the initial doses of the two drugs (group A: 9 +/- 3 min, group B: 6 +/- 3 min, group C: 11 +/- 4 min, group D: 7 +/- 2 min). Continuing the muscle relaxation proved easier with the suxamethonium; signs of decurarization occurred rather unexpectedly with vecuronium. No adverse effect was seen with vecuronium, whilst the diastolic blood pressure rose 20% during the first 25 min following the administration of suxamethonium. It can be concluded that, in the absence of monitoring of the curarization, the repeated administration of vecuronium with a first dose of 0.05 mg X kg-1 brought few advantages compared with the continuous infusion of suxamethonium.

50 patients selected at random were given vecuronium (group A) or pancuronium bromide (group B) at an initial dose of 0.05 mg X kg-1, followed by repeat injections of 0.0125 mg X kg-1. 34 other patients, separated in two groups: group C (vecuronium) and group D (pancuronium), received stronger doses of both drugs: 0.07 mg X kg-1 initially, followed by 0.022 mg X kg-1 repeat injections. The four groups were anaesthetized according to the same protocol; the patients underwent gastrointestinal and gynaecological surgery, lasting 122 +/- 50 min. The results showed that the time of onset and the duration of action of vecuronium were shorter, and that increasing the dose did not increase significantly the duration of action of these repeat doses: time of onset: 104 +/- 42 s (group A), 205 +/- 36 s (group B), 96 +/- 23 s (group C), 255 +/- 36 s (group D); duration of action: 19 +/- 6 min (group A), 36 +/- 6 min (group B), 24 +/- 7 min (group C), 43 +/- 13 min (group D); mean time between doses: 26 +/- 10 min (group A), 55 +/- 5 min (group B), 33 +/- 7 min (group C), 49 +/- 3 min (group D). The degree of muscle relaxation was always satisfactory in the four groups. Decurarization appeared to be particularly sudden with vecuronium. Neither an abnormally prolonged duration of action, nor any haemodynamic effect, nor any signs of histamine release were seen.

Vecuronium, a new non-depolarizing muscle relaxant, was more powerful than d-tubocurarine, gallamine and alcuronium. Its muscle blocking effect was similar to that of pancuronium. It had a smaller distribution volume and a quicker elimination half-life than the other non-depolarizing muscle blocking drugs. The time of onset and duration of action, as well as the time for recovery were also shorter, being 3-5 min, 17-22 min and 25 min respectively. The accumulation of vecuronium in the body was low; increasing the dose increases the duration of action, but not the recovery time. No adverse effect has been reported as yet. Compared with suxamethonium, a depolarizing muscle relaxant, it had a longer time of onset and duration of action. Vecuronium cannot therefore replace suxamethonium for endotracheal intubation.