Chemical
A benzyl isoquinolonium ester.
It is a short-acting relaxant which is rapidly broken down by the body. This makes atracurium very predictable, as it wears off rapidly compared with the longer-acting relaxants.
Cardiovascular effects
Although atracurium produces few direct circulatory effects, the absence of vagal blocking activity makes the patient vulnerable to bradycardias during anaesthesia. Histamine release may occur with doses of atracurium greater than 0.6 mg/kg. Histamine may also be released if atracurium precipitates in the syringe or vein. This may occur if atracurium is injected immediately after thiopentone.
Respiratory effects
In standard doses, atracurium rarely causes problems with bronchospasm. Bronchospasm can occasionally occur secondary to histamine release.
Placental transfer is insignificant and the drug is widely used in obstetrics.
Distribution, metabolism and excretion
Atracurium is broken down to inactive metabolites by (minor) ester hydrolysis and spontaneous Hoffman degradation (major pathway) to Laudanosine. This metabolite has been shown to cause seizures in animal models >17 mcg/ml). There is little change in its effects in patients with renal or liver failure. When used for long operations, it is very predictable.
Dose, administration and use
A dose of 0.3-0.6 mg/kg will provide relaxation for 20-40 minutes. Supplemental doses should be 5-10 mg.
Contraindications
Atracurium precipitates in an alkaline pH and it should never be mixed with thiopentone. Always flush the vein with saline if using the two drugs at induction.
Storage
Should be kept in a refrigerator at 4 degrees C, as the drug deteriorates at room temperature.
ArticleDate:20040405
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