Chronic Tumor-Related Pain
Chronic Tumor-Related Pain
For patients who are able to swallow, oral routes are preferred to parenteral routes to avoid complications such as injection-site discomfort, difficulty of administration, and infection. Transdermal administration (via fentanyl and buprenorphine patches) is a suitable route for patients who find compliance difficult or who cannot tolerate morphine. Fentanyl and methadone are appropriate opioids for patients with reduced renal function, as these drugs are metabolized primarily by the liver. Intravenous (IV), intramuscular (IM), and subcutaneous (SQ) injections are alternative drug-delivery methods that may be considered in patients with advanced disease who require high opioid doses. Parenteral routes are available for morphine, hydromorphone, oxymorphone, levorphanol, fentanyl, and methadone, although IM injections typically are avoided because of unappreciable pharmacokinetic advantage and increased injection-site pain relative to IV and SQ routes. The IV dose of opioids is approximately 33% of the oral dose.
Owing to interpatient variability and an erratic pharmacodynamic profile, methadone is best administered by an experienced practitioner in order to prevent accidental overdose or inadequate pain-relief titration. Buprenorphine (a partial mu receptor agonist and kappa receptor antagonist) and tramadol (a centrally acting drug with mixed mechanisms) are other analgesic options. Tramadol should not be used concomitantly with monoamine oxidase inhibitors, and its use in patients with a history of seizures or concomitant antidepressants should be carefully evaluated prior to initiation because of the increased risk of seizure or serotonin syndrome.
Routes of Opioid Administration
For patients who are able to swallow, oral routes are preferred to parenteral routes to avoid complications such as injection-site discomfort, difficulty of administration, and infection. Transdermal administration (via fentanyl and buprenorphine patches) is a suitable route for patients who find compliance difficult or who cannot tolerate morphine. Fentanyl and methadone are appropriate opioids for patients with reduced renal function, as these drugs are metabolized primarily by the liver. Intravenous (IV), intramuscular (IM), and subcutaneous (SQ) injections are alternative drug-delivery methods that may be considered in patients with advanced disease who require high opioid doses. Parenteral routes are available for morphine, hydromorphone, oxymorphone, levorphanol, fentanyl, and methadone, although IM injections typically are avoided because of unappreciable pharmacokinetic advantage and increased injection-site pain relative to IV and SQ routes. The IV dose of opioids is approximately 33% of the oral dose.
Owing to interpatient variability and an erratic pharmacodynamic profile, methadone is best administered by an experienced practitioner in order to prevent accidental overdose or inadequate pain-relief titration. Buprenorphine (a partial mu receptor agonist and kappa receptor antagonist) and tramadol (a centrally acting drug with mixed mechanisms) are other analgesic options. Tramadol should not be used concomitantly with monoamine oxidase inhibitors, and its use in patients with a history of seizures or concomitant antidepressants should be carefully evaluated prior to initiation because of the increased risk of seizure or serotonin syndrome.
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