Pethidine RIMAs

Many cases of serious (some fatal) adverse effects have been reported when pethidine is added to a RIMA. 

The UK manufacturer of linezolid (a drug with weak, reversible, non-selective MAOI activity) contraindicates its use with pethidine, unless facilities are available for close observation and monitoring of blood pressure, because of the possibility of serious reactions, as have occurred with classical MAOIs and pethidine, see MAOIs or RIMAs -I- Opioids Pethidine (Meperidine) , p.1140. 

Apart from these two isolated reports, there seems to be no other clinical evidence of adverse interactions between MAOIs and dextropropoxyphene. For reports of the serotonin syndrome seen with pethidine (meperidine) and MAOIs, see MAOIs or RIMAs + Opioids Pethidine (Meperidine) , p.ll40. 

The concurrent use of pethidine and MAOIs has resulted in a serious and potentiaiiy iife-threatening reaction in several patients, and one possibie case has been reported with mociobemide. Excitement, muscie rigidity, hyperpyrexia, flushing, sweating and unconsciousness can occur very rapidiy. Respiratory depression and hypertension or hypotension have aiso been seen. Pethidine shouid not be given to patients taking any MAOI or RIMA. 

The interaction between pethidine and the MAOIs, which was first observed in the mid-1950s, is based on case reports. One case has been reported with RIMA mociobemide. It is serious and potentially fatal. Its incidence is unknown, but it is probably quite low, because one study that attempted to produce the interaction by giving increasing test doses of pethidine to 15 patients taking various MAOIs did not show the interaction. It may therefore be an idiosyncratic reaction. Nevertheless, it would be imprudent to give pethidine to any patients on an MAOI or RIMA. Bear in mind that the older MAOIs are all essentially irreversible so that an interaction is possible for many days after their withdrawal (at least 2 weeks is the official advice), whereas the newer RIMAs (e.g. mociobemide) are reversible and unlikely still to interact 48 hours after they have been stopped. 

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