Diclofenac does not modify morphine bioavailability in cancer patients

Pharmacological data science perspective on fatal incidents of morphine treatment

Morphine prescribed for analgesia has caused drug-related deaths at an estimated incidence of 0.3% to 4%. Morphine has pharmacological properties that make it particularly difficult to assess the causality of morphine administration with a patient's death, such as its slow transfer between plasma and central nervous sites of action and the existence of the active metabolite morphine-6-glucuronide with opioid agonistic effects, Furthermore, there is no well-defined toxic dose or plasma/blood concentration for morphine. Dosing is often adjusted for adequate pain relief. Here, we summarize reported deaths associated with morphine therapy, including associated morphine exposure and modulating patient factors such as pharmacogenetics, concomitant medications, or comorbidities. In addition, we systematically analyzed published numerical information on the stability of concentrations of morphine and its relevant metabolites in biological samples collected postmortem. A medicolegal case is presented in which the causality of morphine administration with death was in dispute and pharmacokinetic modeling was applied to infer the administered dose. The results of this analytical review suggest that (i) inference from postmortem blood concentrations to the morphine dose administered has low validity and (ii) causality between a patient's death and the morphine dose administered remains a highly context-dependent and collaborative assessment among experts from different medical specialties.

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.

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.

Nimesulide and diclofenac in the control of cancer-related pain. Comparison between oral and rectal administration

64 patients with pain associated with advanced cancer were treated with either nimesulide or diclofenac as initial analgesia. Patients were randomly allocated to 1 of 4 treatment groups: oral nimesulide 300 mg/day; oral diclofenac 150 mg/day; rectal nimesulide 400 mg/day; and rectal diclofenac 200 mg/day. After 1 week of treatment, both drugs provided an adequate degree of pain relief and allowed an increase in sleep duration. There were no significant differences in efficacy between the drugs or routes of administration. Fewer side effects were observed with nimesulide, giving this agent a better therapeutic index than the reference compound.