MAOIs and anaesthesia
Myth: One cannot give an anaesthetic without ceasing MAOIs first.
The main issue in most operations, and post-operative periods, is the avoidance of analgesics that act as SRIs, viz. meperidine (pethidine), tramadol, dextromephorphan and pentazocine. Other opioids like codeine, oxycodone, morphine, fentanyl, are safe (see (1).
The idea that an anaesthetic cannot be given without first ceasing MAOIs is yet another of the deeply embedded and ill-founded concerns that one encounters. Sadly, it is not inconsequential, because poorly informed careless surgeons (some of whom would struggle to spell ‘pharmacology’) may tell patients due for elective surgery to cease treatment, sometimes without being aware of their history. I have had experience of suicides from relapse of depression as a direct result of such ill-advised cessation of treatment. Therefore, my disparaging view of those surgeons who are too ignorant and arrogant to ask advice, or even inform the prescribing specialist that they have ceased the treatment, will be understandable to some.
In ‘uncomplicated’ anaesthesia, apart from avoiding any use of narcotic analgesics with SRI potency, there are no major problems or interactions. The preponderance of published opinion is, fortunately, lining up behind that view (2-9).
For ‘major’ operations that might require treatment to raise or lower blood pressure there are some minor adjustments of dosage and agents that may be required, but there are no major obstacles. For instance, the hypotensive effect of MAOIs may mean that intra-operative hypotensive measures may be potentiated, and accordingly doses of such drugs may need to be lower. On the other hand, if vasopressor agents are required then directly acting alpha agonists may have their effects slightly potentiated, that means norepinephrine, epinephrine and phenylephrine doses may need to be slightly lower when used in patients on MAOIs. Since ephedrine has releaser potency it is best avoided.
Keywords: MAOI, anaesthesia, safety, drug combinations; drug–drug interactions
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