Advances In The Studies And Clinical Application Of Remifentanil

Remifentanil is a new congener of the fentanyl family of opioids that was approved for use as a supplement to general anesthesia by the US Food and Drug Administration in 1996. The unique feature of remifentanil is its short- acting pharmacokinetic profile. Its ester structure renders it susceptible to widespread ester hydrolysis, resulting in very rapid metabolism.Remifentanil thus constitutes the first true 'ultrashort- acting' opioid, has its greatest advantage in enhancement of 'fast tracking' anaesthesia. Now , remifentanil is in widespread clinical use in numerous countries. The review first considers advances in our knowledge of the pharmacokinetics and pharma codynamics of this agent, and then addresses new developments in its clinical application.Recently, the pharmacokinetics of the major metabolite, remifentanil acid have been described and modelled. During prolonged infusions of remifentanil, the principal metabolite, remifentanil acid, accumulates and may attain concentrations up to 100 times higher than the parent drug. Nevertheless, the metabolite is of very low potency and even after prolonged remifentanil infusion into patients with severe renal impairment, prolongation of μ -opioid effects seems unlikely. one study demonstrated the importance of obtaining arterial samples when attempting to characterize remifentanil pharmacokinetics and pharmacodynamics(i.e. the arterial concentration is much more closely linked to the drug effect). Recent studies using more clinically oriented drug effect measures have, For example, a study using the ventilatory response to the rebreathing of carbon dioxide contrasted the relative potency of remifentanil and alfentanil. That study suggested that remifentanil is about 40-70 times more potent than alfentanil, Another study that compared the psychomotor effects of remifentanil and alfentanil also suggested, in contrast to previously published data based on electroencephalography , that remifentanil appears to be at least 40 times more potent than alfentanil.