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Gallamine
General information
Gallamine is a non-depolarizing muscle relaxant. For intubation, a dose of about 2 mg/kg (some authors say 3–4 mg/kg) is necessary, and the duration of effect is then similar to the usual intubating doses of d -tubocurarine or pancuronium. A dose of 1–1.5 mg/kg is usually sufficient to produce apnea and adequate abdominal relaxation. Such doses are said to be short-acting (20 minutes) but can provide clinical relaxation (75% or more depression of twitch height) for some 30–40 minutes. Individual variation is considerable, and complete spontaneous reversal of blockade is relatively slow.
Organs and systems
Cardiovascular
Tachycardia invariably accompanies the use of gallamine. It is seen after doses as low as 20 mg and reaches a maximum at around 100 mg in adults [ ]. It is often extreme, rates above 120 per minute being not uncommon. The increase in heart rate outlasts the neuromuscular blocking effect [ ]. Usual clinical doses also result in a slight increase in mean arterial pressure, a slight fall in systemic vascular resistance, and a marked rise in cardiac index [ , ]. These cardiovascular effects are principally accounted for by the strong vagolytic action of gallamine, the cardiac muscarinic receptors being almost as sensitive to its blocking action as the acetylcholine receptors of the neuromuscular junction [ ]. Blockade of noradrenaline reuptake and an increased release of noradrenaline from cardiac adrenergic nerve endings [ , ] may contribute, although an inotropic effect in man is disputed [ ]. Ganglion-blocking activity is slight and is not seen in the usual dose range. The possible mechanisms have been reviewed [ ]. Gallamine should therefore not be used when tachycardia has to be avoided.
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