The World Health Organization (WHO) recommends a pain ladder for managing analgesia. In the treatment of chronic pain, whether due to malignant or benign processes, the three-step WHO Analgesic Ladder provides guidelines for selecting the kind of analgesia.
- Mild pain
Paracetamol, or a non-steroidal anti-inflammatory drug (NSAID) such as ibuprofen can be used.
- Mild to moderate pain
Paracetamol, an NSAID and/or paracetamol in a combination product with a weak opioid, may provide greater relief than their separate use.
- Moderate to severe pain
When treating moderate to severe pain, the type of the pain, acute or chronic, needs to be considered. Certain medications may work better for acute pain, others for chronic pain, and some may work equally well on both. Acute pain medication is for rapid onset of pain such as from trauma or to treat postoperative pain. Chronic pain medications are meant for alleviating long-lasting, ongoing pain.
Morphine is the gold standard to which all narcotics are compared. Fentanyl has the benefit of less histamine release and thus fewer side effects. It can also be administered via transdermal patch which is convenient for chronic pain management. Oxycodone is used for relief of serious chronic pain; its main slow-release formula is known as OxyContin, and its short-acting tablets, are available making it suitable for acute intractable pain or breakthrough pain.
Opioid medications can provide a short, intermediate or long acting analgesia depending upon the specific properties of the medication and whether it is formulated as an extended release drug. Although opioids are strong analgesics, they do not provide complete analgesia regardless of whether the pain is acute or chronic in origin. Opioids are efficacious analgesics in cancer pain and only modestly effective in non-malignant pain management. When opioids are used for prolonged periods, drug tolerance, chemical dependency, diversion and addiction may occur.
Clinical guidelines for prescribing opioids for chronic pain have been issued by the Pain Association of Singapore. Included in these guidelines is the importance of assessing the patient for the risk of substance abuse, misuse, or addiction; a personal or family history of substance abuse is the strongest predictor of aberrant drug-taking behaviour. The guidelines also recommend monitoring not only the pain but also the level of functioning and the achievement of therapeutic goals.
Antidepressants and antiepileptic drugs
Some antidepressant and antiepileptic drugs are used in chronic pain management and act primarily within the pain pathways of the central nervous system, though peripheral mechanisms have been attributed as well. These mechanisms vary and in general are more effective in neuropathic pain disorders as well as complex regional pain syndrome. Drugs such as gabapentin have been widely prescribed for the control of chronic pain or neuropathic pain.
Other drugs are often used to help analgesics combat various types of pain, and parts of the overall pain experience, and are hence called adjuvant medications. Orphenadrine and cyclobenzaprine are also muscle relaxants, and therefore particularly useful in painful musculoskeletal conditions. Clonidine has found use as an analgesic for this same purpose.