The pharmacological management of cancer pain. Part 1: The role of non opioid and adjuvant drugs

The management of pain in the oncology patient

The treatment of cancer pain is improving, but pain remains a significant problem. Although better analgesics with greater efficacy and fewer side effects are needed, the most significant problem regarding the appropriate management of cancer pain remains a lack of knowledge among physicians treating cancer patients. Cancer management should be undertaken within a palliative care model, in which autonomy and respect for individuals and their families guides all aspects of care.

The use of anti-inflammatory drugs in cancer pain

The role of non-steroidal anti-inflammatory drugs (NSAIDs) in cancer pain has been well established in the treatment of mild pain and also alone or in association with opioids for the treatment of moderate to severe pain. Acutely, NSAIDs may be more than mild analgesics, and may provide additional analgesia when combined with opioids. However, NSAIDs have ceiling effects and there is no therapeutic gain from increasing dosages beyond those recommended. As there is no clearly superior NSAID, the choice should be based on experience and the toxicity profile that probably relates to the COX-1:COX-2 ratio. Among the older drugs, ibuprofen seems to have these properties.Non-steroidal anti-inflammatory drugs have been shown to have an opioid-sparing effect. Although the value of a simple narcotic-sparing effect may be questioned in cancer pain treatment, the use of NSAIDs may be useful when the increase in opioid dosage determine the occurrence of opioid toxicity. Like opioids, NSAIDs should not be considered analgesics for a specific type or cause of pain. There is a lack of evidence for any difference between different routes of NSAIDs administration. The long-term toxicity of NSAIDs in cancer pain is poorly defined due to a lack of studies. A variety of strategies have been used in an attempt to reduce the risks associated with NSAID therapy. Those NSAIDs that are weak COX-1 inhibitors may be preferred. In addition, concomitant administration of misoprostol is recommended in patients at increased risk for upper gastrointestinal complications.

Analgesic effects of nonsteroidal anti-inflammatory drugs in cancer pain due to somatic or visceral mechanisms

The role of nonsteroidal anti-inflammatory drugs (NSAIDs) is well established in the treatment of cancer pain. This class of drugs is considered particularly effective in pain due to somatic mechanisms, although proof of this observation is lacking. To ascertain whether NSAIDs are more effective in specific nociceptive forms of cancer pain, they were administered alone or added to opioids in 32 patients with a sole pain mechanism, somatic pain due to bone metastases (17 patients) or visceral pain (15 patients), respectively. Pain intensity, mean doses of opioids used, and symptoms were recorded after starting NSAID. A significant reduction in pain intensity was found at 3, 7, and 14 days. No differences in pain intensity between the two groups were observed. However, patients with a visceral mechanism required higher opioid doses after a week of treatment. No differences in adverse effects were reported. NSAIDs may be useful drugs in the management of cancer pain, regardless of the mechanism of pain involved. The incidence of adverse effects during prolonged administration should be assessed in future studies.

Opioid-sparing effect of diclofenac in cancer pain

This study investigated the opioid-sparing effect of diclofenac using patient-controlled analgesia with oral methadone. Fifteen patients with advanced cancer participated. After achieving adequate analgesia with regular dosing of oral methadone (T1), patient-controlled analgesia with methadone was administered for 3 days (T2). Intramuscular diclofenac 75 mg twice daily was then added to this regimen for 3 days (T3). Compared to T2 values, methadone dose was significantly reduced at T2 and T2, and pain report (recorded on a visual analogue scale) was significantly reduced at T3. A reduction in methadone plasma concentration was also observed at T2 and T3, although it did not attain statistical significance. Significant decreases in the intensity of several symptoms other than pain were also found at T2 and T3. Diclofenac appears to have a relevant opioid-sparing effect when using patient-controlled analgesia with oral methadone.

Nonopioid agents for treatment of acute and subacute pain

OBJECTIVE

To review the available nonopioid options for alleviating pain.

DESIGN

The various categories of adjuvant agents and their mechanisms of action in the treatment of pain are summarized.

MATERIAL AND METHODS

Adjuvant therapies that directly diminish acute and subacute pain, those that counteract the side effects of opioids, and those that help manage concurrent psychiatric symptoms are discussed, and their recommended doses and adverse effects are outlined.

RESULTS

Adjuvant medications such as nonopioid analgesics (including acetaminophen and nonsteroidal anti-inflammatory drugs), corticosteroids, anticonvulsants, antidepressants, muscle relaxants, and antispasmodics can directly decrease pain. The three most common problems associated with opioid therapy are nausea, constipation, and sedation. Adjuvant drugs such as antiemetics, laxatives, and psychostimulants may counteract these side effects of opioids and thereby enable patients to tolerate adequate doses of opioid agents to relieve pain. In addition, adjuvant medications such as antidepressants, anxiolytics, and antipsychotics can be used to treat concomitant psychiatric symptoms that develop and aggravate existing pain. The choice of agents must be individualized to the patient's particular pain condition; once therapy has been initiated, the response must be continually monitored to optimize control of pain.

CONCLUSION

Nonopioid adjuvant agents should be considered an integral part of the management of acute and subacute pain.