Emerging analgesics in cancer pain management.

Cancer pain is one of the most frequent symptoms in malignant disease, severely impairing the patients' quality of life. The recommendations of the World Health Organization will provide adequate pain relief for the vast majority of cancer patients. However, some patients will suffer from inadequate analgesia or intolerable side effects. Cyclooxygenase-2 (COX-2)-selective non-steroidal anti-inflammatory drugs (NSAIDs), new anticonvulsants, cannabinoids and NMDA receptor antagonists are being developed for these patients. NSAIDs with nitric oxide-releasing moieties are an interesting addition, as this new class of analgesics combines improved analgesic efficacy with higher tolerability. Conotoxins and other drugs such as nicotinic acetylcholinergic receptor agonists will be advantageous only for a few patients in the near future, as side-effect profile and risk of complications, as well as the burden on the patient, often are not worth the additional analgesic benefit.