[Treatment of pain in cancer with systemically administered opioids].

The World Health Organization guidelines for cancer pain relief have been proven efficacious in 90% of the patients with cancer pain. The patient's self-report of pain is the focus of treatment. When initiating treatment, controlled-release preparations of opioids are generally favoured, and are combined with immediate release morphine to prevent or treat 'breakthrough' pain and to enable the optimum opioid dosage to be calculated. (Breakthrough pain is a transient increase in pain in a patient who has stable, persistent pain treated with opioids.) In patients with an unfavourable balance between analgesia and side effects, the following strategies may be useful, together with appropriate treatment of the side effects: Sequential opioid trials (so-called opioid rotation) is an approach which is effective in 50-70% of the patients. Changing the route of opioid administration is successful in 70-95% of the patients. When selecting an invasive technique, continuous subcutaneous infusion is medically preferred. Spinal analgesia is an alternative. Knowledge of the relative potency of opioid drugs and of their biologic availability is needed to guide changes in drugs or routes of administration.