Meperidine [Pethidine]

Meperidine pharmacotherapy is recommended only for short-term symptomatic pain management. Repeated doses result in the accumulation of a toxic metabolite, normeperidine. Normeperidine has a relatively long half-life of elimination and can cause several problematic adverse drug reactions including dysphoria, irritability, myoclonus, and seizures. Meperidine is less effective when ingested orally than when injected intramuscularly, intravenously, or subcutaneously. Poor drug absorption following oral ingestion generally requires higher oral dosages. Meperidine appears to elicit its analgesic and CNS and respiratory depressant actions primarily by binding to the endorphin receptors in the CNS. Meperidine has several therapeutic actions qualitatively similar to those of morphine, one of which is analgesia. When injected in doses of 80 to 100 mg, meperidine is approximately equivalent in analgesic action to 10 mg of morphine. Meperidine can produce addiction and habituation similar to that associated with morphine and other opiate analgesics.