Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Nimbex (Glaxo Wellcome)
2 mg/mL in 2.5 mL and 5 mL ampoules
5 mg/mL in 30 mL vials
Indication: muscle relaxation
Atracurium is a non-depolarising neuromuscular blocker. The molecule has several isomers, one of which is cisatracurium. This isomer also causes neuromuscular blockade, probably by competing for cholinergic receptors on the motor end-plate. It is probably more potent than atracurium.
For tracheal intubation, cisatracurium is given as a bolus injection. During surgery or mechanical ventilation, neuromuscular blockade can be maintained by repeat injections or an infusion. After a bolus dose, the patient will be ready for intubation in 2-3 minutes. Higher doses shorten the time to onset of neuromuscular block, but this increases the time to spontaneous recovery. In general, cisatracurium has an intermediate duration. Depending on the dose given, spontaneous recovery is complete within an hour. Recovery can be speeded by giving an anticholinesterase.
As cisatracurium degrades in the body, its elimination is largely organ independent. No dose alterations are required in hepatic or renal failure.
Cisatracurium appears to be as safe as atracurium. Adverse effects include bronchospasm, bradycardia, hypotension, rashes and flushing. The risk of histamine release is unlikely to be greater than that of atracurium. The effect of cisatracurium is influenced by interactions with many commonly used drugs.
At present, it is uncertain if cisatracurium will have any significant clinical advantages over atracurium.
