[Drug therapy for tumor pain I. Properties of non-opioids and opioids.].

Analgesic pharmacotherapy represents one of the major approaches to the treatment of cancer pain, since it is used in almost every patient. A thorough evaluation of the physical and mental status of the patient and of the pain is as necessary as a sound understanding of the pharmacokinetic and pharmacodynamic characteristics of the analgesics selected. The World Health Organization (WHO) has issued a basic 3 stage progression for the treatment of cancer pain, the "WHO Analgesic Ladder". Assignment to the stages depends mainly on the intensity of the pain rather than on its specific aetiology. Mild to moderate pain is treated with non-opioid drugs; moderate to severe pain, with a combination of a "weak" opioid and a non-opioid; and "strong" opioids should be used in combination with a non-opioid in the case of severe pain. Adjuvant drugs can be added if specifically indicated. Nonopioid analgesics include non-acidic compounds, e. g. paracetamol and metamizole, and acidic non-opioids, e. g. acetylsalicylic acid and newer non-steroidal anti-inflammatory drugs (NSAID). In contrast to most of the opioid analgesics, they have a ceiling effect for analgesia. Addiction and tolerance are extremely rare concerns. Opioids can be subgrouped into "weak" (e. g., codeine, dextropropoxyphene) and "strong" opioids (e. g., morphine) and also into drugs interacting with different opioid-receptor subtypes. Whereas pure agonists (e. g., morphine) produce increasingly intense analgesia with increasing dose, partial agonists and agonist-antagonists have a ceiling effect for analgesia and therefore have only a minor role in the treatment of chronic pain in cancer patients. Adverse effects occur in most patients in a dose-dependent manner. The most common of these is constipation; nausea, vomiting and sedation occur mostly at the start and can usually be treated effectively. The appropriate dosage, route of administration and dosage scheme of analgesics needs to be worked out for each individual patient in intensive work with the patient and a close follow-up, for years if necessary. Some analgesics may not be available in some countries, or only in specific preparations.