Bedside perspectives on the use of opioids: Transferring results of clinical research into practice

1. Transference of research findings to clinical practice has been a challe nge for those managing chronic pain. Generally, pain is not well controlled in hospitals and steps need to be taken to make pain control more effectiv e. 2. Clinical trials of opioids have shown that pain can be controlled in the great majority of patients. Apart from the use of the World Health Organiz ation Analgesic Ladder, a 'pain diagnosis' should be made and a comprehensi ve view of pain needs to be considered by the clinician. This would include pain and other physical symptoms, psychological issues and social and spir itual stresses. 3. Respiratory depression and tolerance for opioids are often seen as negat ive aspects of opioids and, therefore, may lead to inadequate control of pa in. The evidence cited suggests that, in the long-term treatment of cancer pain, respiratory depression almost never occurs. The only situation that w arrants caution is when an anaesthetic block or similar procedure relieves pain treated by opioids, when that patient has been receiving large doses o f opioids. Long-term studies with opioids show that tolerance may occur, bu t is not a clinical problem and should not impair their use in adequate dos es to relieve the patient's pain. 4. The active morphine metabolites, morphine-3-glucuronide (M3G) and morphi ne-6-glucuronide (M6G) do need to be considered when administering morphine . There seems to be considerable interindividual variation in the productio n and elimination of metabolites. In cases of renal failure or in the elder ly, the ratios of M3G and M6G to morphine accumulate exponentially, making opioid toxicity more likely. Even different routes of administration seem t o be associated with different ratios of metabolites. A knowledge of these sources of pharmacokinetic variability may lead to more effective use of th e opioids in clinical practice.