Practical guidelines concerning food restrictions and monoamine oxidase inhibitors are requested. W

Fråga: Practical guidelines concerning food restrictions and monoamine oxidase inhibitors are requested. What differences are there between reversible, selective and irreversible, non-selective monoamine oxidase inhibitors?

Sammanfattning: With irreversible MAOIs, intake of any spoiled or fermented food should be avoided, as well as aged cheese, dried sausage, fava beans, soy sauce, yeast extracts, sauerkraut and tap beer. Moderate amounts of bottled beer or wine are allowed. Treatment with reversible, selective MAOIs does not necessitate any dietary restrictions.

Svar: Monoamine oxidase inhibitors (MAOIs, eg tranylcypromine) were developed in the 1950s as the first effective pharmacological treatment of depression. The enthusiasm over this new therapeutic option diminished as severe interactions between MAOIs and tyramine-containing food were discovered. Since then have reversible and selective MAO-A inhibitors (eg moclobemide), with a much lesser risk of interactions, been introduced (1).

Food-derived tyramine, a sympathomimetic amine which stimulates the release of noradrenaline, is usually metabolised by intestinal MAO-A and very little reaches the systemic circulation. In combination with MAOIs, the bioavailability of tyramine increases and also the level of noradrenaline in the synaptic cleft increases (due to the accumulation caused by the MAOI) which may lead to hypertensive crises. Treatment with traditional, irreversible MAOIs is therefore combined with dietary restrictions. The literature concerning these restrictions is large and varying. Tyramine is formed by protein fermentation and is mainly present in matured or fermented food, such as cheese, beer, dry sausage and sauerkraut. Numerous case reports over the years have (often uncritically) added forbidden types of food to the list. However, several review articles, trying to revise these lists, have also been published (1-3). Apparently, one problem is the varying content of tyramine both between and within different types of food. Also, other vasoactive amines (histamine, octopamine, or phenylephrine) may contribute to the tyramine effect in some cases.

According to a tyramine pressor test, the amount of tyramine that has to be ingested together with food to give a 30 mmHg rise in systolic blood pressure in untreated, healthy subjects was approximately 1300 mg. The corresponding amount for 8 subjects treated with 600 mg moclobemide daily was 300 mg (range 150-500 mg) and during treatment with tranylcypromine 35 mg (range 20-50 mg) (4). Other authors have suggested that more than 8 or 25 mg might be potentially dangerous in tranylcypromine treated patients (1).

As mentioned above, the tyramine content in different food stuffs may vary considerably according to different sources. More than 1000 mg/kg may be found in aged cheese, yeast extract and pickled herring and between 100-1000 mg/kg in dried sausage, soy sauce, beef liver, pepperoni, salted herring and smoked ham, according to (5). In Sweden, irreversible MAOIs can only be prescribed with a special licence from The Swedish Medical Product Agency (MPA). Patients are advised to avoid intake of all cheese, yeast extracts, any spoiled or fermented food, any meat, fish or sausage that has been stored or dried for a period of time, chicken liver, Italian fava beans, beer and aspartame (6). The authors of a recent review have tried to critically minimise the dietary restrictions, by literature studies and tyramine measurements. They used a tyramine content of less than 6 mg/serving as a safety threshold. Their list resembles that of the Swedish MPA, adding sauerkraut, but excluding properly stored pickled or smoked fish, fresh cheese, such as cottage cheese or cream cheese and moderate amounts of bottled beer or wine (less than 2 bottles or glasses) (1). Fresh liver (chicken or beef) is probably safe also (2).

With reversible MAOIs more than 300g of an aged cheese would have to be ingested in a single meal to produce any significant risk (4).