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 challenge for those managing chronic pain. Generally, pain is not well controlled in hospitals and steps need to be taken to make pain control more effective. 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 Organization Analgesic Ladder, a 'pain diagnosis' should be made and a comprehensive view of pain needs to be considered by the clinician. This would include pain and other physical symptoms, psychological issues and social and spiritual stresses. 3. Respiratory depression and tolerance for opioids are often seen as negative aspects of opioids and, therefore, may lead to inadequate control of pain. The evidence cited suggests that, in the long-term treatment of cancer pain, respiratory depression almost never occurs. The only situation that warrants caution is when an anaesthetic block or similar procedure relieves pain treated by opioids, when that patient has been receiving large doses of opioids. Long-term studies with opioids show that tolerance may occur, but is not a clinical problem and should not impair their use in adequate doses to relieve the patient's pain. 4. The active morphine metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) do need to be considered when administering morphine. There seems to be considerable interindividual variation in the production and elimination of metabolites. In cases of renal failure or in the elderly, the ratios of M3G and M6G to morphine accumulate exponentially, making opioid toxicity more likely. Even different routes of administration seem to be associated with different ratios of metabolites. A knowledge of these sources of pharmacokinetic variability may lead to more effective use of the opioids in clinical practice.
Ravenscroft
P
P
University of Newcastle, New South Wales, Australia. mdpr@cc.newcastle.edu.au
Schneider
J
J
D000701:Analgesics, Opioid / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006801:Humans; D010146:Pain / Q000188:drug therapy*; D010601:Pharmacology, Clinical; D012106:Research
D000701:Analgesics, Opioid