Posted by ed_uk on November 18, 2004, at 15:17:27
In reply to Re: Ketamine Experiences /Ketamine and MAOIs » SLS, posted by cubbybear on November 18, 2004, at 9:23:49
Anaesthetics, general + Monoamine oxidase inhibitors (MAOIs)
It used to be thought that MAOIs should be withdrawn well before anaesthesia, but there is now evidence that this may be unnecessary in most patients, although individual cases of both hypo- and hypertension have been seen. The MAOIs can however interact with other drugs sometimes used during surgery.Clinical evidence and mechanism
The absence of problems during emergency general anaesthesia in 2 patients on MAOIs prompted further study in 6 others taking unnamed MAOIs chronically. All 6 were premedicated with 10–15 mg diazepam 2 h before surgery, induced with thiopental (thiopentone), given suxamethonium (succinylcholine) before intubation, and maintained with nitrous oxide/oxygen and either halothane or isoflurane. Pancuronium was used for muscle relaxation. Morphine was given postoperatively. One patient experienced hypotension that responded to repeated intravenous doses of 0.1 mg phenylephrine without hypertensive reactions. No other untoward events occurred either during or after the anaesthesia. 1No adverse reactions occurred in 27 other patients on MAOIs (tranylcypromine, phenelzine, isocarboxazid, pargyline) when anaesthetised. 2 No problems were seen in eight patients on unnamed MAOIs when anaesthetised, nor in dogs on tranylcypromine given enflurane and fentanyl. 3 Two single case reports describe the safe and uneventful use of propofol in a patient on phenelzine 4 and another on tranylcypromine. 5 The latter was also given alfentanil. No problems were seen in one patient on tranylcypromine when given ketamine 6 and in another on selegiline when given fentanyl, isoflurane and midazolam. 7 No problems were seen in another patient on phenelzine when anaesthetised firstly with sevoflurane in oxygen, followed by isoflurane, oxygen, air and an infusion of remifentanil. 8 Unexplained hypertension has been described in a patient taking tranylcypromine when etomidate and atracurium were used. 9 Moclobemide was stopped on the morning of surgery in a patient who was anaesthetised with propofol and later isoflurane in nitrous oxide and oxygen. Morphine and droperidol were also used. No adverse reactions occurred. 10 Ketorolac, propofol and midazolam were used uneventfully in one patient on phenelzine. 11
Importance and management
There seems to be little documentary evidence that the withdrawal of MAOI before anaesthesia is normally necessary. Scrutiny of reports 12 alleging an adverse reaction usually shows that what happened could be attributed to an interaction between other drugs used during the surgery (e.g. pethidine, sympathomimetics) rather than with the anaesthetics. The authors of the reports cited 1,2 here offer the opinion that . . general and regional anaesthesia may be provided safely without discontinuation of MAOI therapy, provided proper monitoring, adequate preparation, and prompt treatment of anticipated reactions are utilised. 1 This implies that the possible interactions between the MAOI and other drugs are fully recognised, but be alert for the rare unpredictable response.
poster:ed_uk
thread:417245
URL: http://www.dr-bob.org/babble/20041118/msgs/417539.html