The most important drug interactions involving opioid analgesics are additive CNS depression with ethanol, sedative-hypnotics, anesthetics, antipsychotic drugs, tricyclic antidepressants, and antihistamines. Concomitant use of certain opioids (eg, meperidine) with monoamine oxidase inhibitors increases the incidence of hyperpyrexic coma. Meperidine has also been implicated in the serotonin syndrome when used with selective serotonin reuptake inhibitors.