REMIFENTANIL, AN ESTERASE-METABOLIZED OPIOID - WHAT ADVANTAGES DOES IT OFFER IN ANALGESIA AND ANESTHESIA

Esterase hydrolysis is a metabolic pathway that can be exploited to in crease the rate of metabolism and elimination and so reduce the durati on of the pharmacodynamic effects of drugs. Previously applied to beta -adrenergic blocking agents and muscle relaxants, this concept was rec ently used to develop an esterase-metabolised opioid, remifentanil. Re mifentanil has a predictable rapid onset, short duration and rapid off set of analgesic effect. This is likely to allow easy titration of ana lgesia to changing anaesthesia requirements during surgery. The metabo lism of remifentanil by nonspecific esterases in the blood and tissues prevents accumulation, even when given at high dosages over prolonged periods. Clinical recovery from anaesthesia is very rapid, irrespecti ve of the age or physical status of the patient or the type or duratio n of surgery. In addition, the non-organ dependent elimination of remi fentanil obviates the usual requirement for opioid dose adjustments in patients with hepatic impairment. Adverse events of remifentanil are those typical of mu-opioid receptor agonists, including respiratory de pression, muscle rigidity, hypotension and bradycardia. Thus, the majo r benefits of remifentanil, the prototype esterase-metabolised opioid, are the achievement of intense, titratable intraoperative analgesia a llowing for rapid clinical recovery without the risk of inducing recur rent postoperative respiratory depression. In addition, residual opioi d activity disappears rapidly following discontinuation of the drug.