Monoamine oxidase inhibitors and narcotic analgesics. A critical review of the implications for treatment.

There has been a recent renewal of interest in the use of monoamine oxidase inhibitors, but the concurrent administration of narcotic analgesics is often a cause for concern. This review clarifies the different types of MAOI/narcotic interactions and offers guidelines for the use of narcotic analgesics in the presence of MAOIs. The MAOI/pethidine interaction has two distinct forms: an excitatory and a depressive form. Pethidine must never be used in the presence of MAOIs because of the risk of a fatal excitatory interaction. Morphine does not cause this excitatory interaction, and is the drug of choice provided an allowance is made for possible potentiation of the depressive narcotic effect. It is inevitable that strong analgesia will occasionally be required as an emergency measure in patients on MAOIs, and insufficient attention is paid in psychiatric textbooks to the two different types of interactions and their therapeutic implications.