EPIDURAL CLONIDINE - A REVIEW OF ITS PHARMACOLOGY AND EFFICACY IN THEMANAGEMENT OF PAIN DURING LABOR AND POSTOPERATIVE AND INTRACTABLE PAIN

Clonidine is an established alpha(2) adrenoceptor agonist with antihyp ertensive properties which, when administered epidurally, has art anal gesic action that is largely mediated by alpha(2) adrenoceptors in the dorsal horn of the spinal cord. After epidural administration, the dr ug undergoes rapid systemic absorption and is able to pass through the placenta. Data from clinical studies evaluating the efficacy of epidu ral clonidine indicate that it is a useful adjunct to opioid and/or lo cal anaesthetic agents for postoperative analgesia after major abdomin al or orthopaedic surgery or after caesarean section. Epidural clonidi ne has also proved to be an effective analgesic that enhances the dura tion of action of local anaesthetic agents during labour without neona tal adverse effects. Continuous infusions of epidural clonidine are ef fective in patients with cancer pain of neuropathic origin. Similarly, the utility of this agent appears to extend to patients with chronic non-cancer pain. At doses producing the desired analgesic effects, sed ation, bradycardia and hypotension are the most common adverse events associated with epidural clonidine. There has been a single report of rebound hypertension after abrupt cessation of epidural clonidine. In conclusion, the available data suggest a role for epidural clonidine a s an adjunctive agent for the control of pain (of postoperative, malig nant or nonmalignant origin and during labour). In particular; it may be useful in patients unsatisfied with opioid or local anaesthetic age nts or in those tolerant to opioids. However the place of epidural clo nidine as an alternative or adjunctive analgesic agent in any given pa tient group is likely to depend on the acceptability of the epidural r oute of administration and haemodynamic and sedative effects of the dr ug.