Physical dependence is a normal physiological response to chronic opioid therapy which may cause withdrawal symptoms if the drug is abruptly stopped.

The signs of physical dependence, or withdrawal, are only seen when administration of morphine is abruptly stopped or an antagonist administered. The withdrawal syndrome is characterised by anxiety and agitation, rhinorrhoea and lacrimation, fever and sweating, muscular and abdominal cramps, tremor and other signs of sympathetic overactivity. The time of onset and duration of the withdrawal syndrome depend on the pharmacokinetics of the opioid in use. Withdrawal syndromes can be effectively treated by administering 25-50% of the previous daily dose, given in divided doses, 6-hourly. Patients whose pain has been relieved by surgical or other means should have their opioid analgesics reduced by 15-25% per day.

Patients need to be reassured that physical dependence does not prevent withdrawal of the medication if their pain is relieved by other means. Physical dependence is not related to the development of psychological dependence.

*36\55\2*