4.3.2 Monoamine-oxidase inhibitors

All irreversible monoamine-oxidase inhibitors (MAOIs) are considered less suitable for prescribing. Potentially life-threatening hypertensive crisis can occur following ingestion of tyramine or other pressor amines in foods or medication (such as ephedrine, pseudoephedrine and phenylpropanolamine).

Tyramine-rich food examples include mature cheese, salami, pickled herring, Bovril®, Oxo®, Marmite® or any similar meat or yeast extract or fermented soya bean extract, and some beers, lagers or wines. Foods containing dopa (such as broad bean pods) should also be avoided. Patients should be advised to eat only fresh foods and avoid food that is suspected of being stale or 'going off'. This is especially important with meat, fish, poultry or offal; game should be avoided. The danger of interaction persists for up to 2 weeks after treatment with MAOIs is discontinued. Patients should also be advised to avoid alcoholic drinks or de-alcoholised (low alcohol) drinks.

Patients should be advised to avoid tyramine-rich or dopa-rich food or drinks whilst taking, or for 2 to 3 weeks after stopping the MAOI. Advise patient to refer to the patient information leaflet (PIL) supplied with the product for detailed dietary restrictions.

Patients should be advised to take last dose before 3pm in order to minimise sleep disturbance/ insomnia.

Due to the risk of postural hypotension and hypertensive crisis, the BNF recommends that patients prescribed MAOIs should have their blood pressure monitored.

Increased caution is required when switching patients to/from an MAOI to another antidepressant. For guidance and support when switching antidepressants, refer to formulary guidance, here.

Non-reversible MAOIs

Phenelzine
  • Tablets 15mg (£18.90 = 15mg three times a day)
    • Supply shortages, see note 3 before prescribing

Indications and dose

  • Depression: 15mg 3 times daily, increased if necessary to 4 times daily after 2 weeks (hospital patients, maximum 30mg 3 times daily), then reduced gradually to lowest possible maintenance dose (15mg on alternate days may be adequate)

Notes

  1. Phenelzine may be considered for patients who have failed to respond to alternative antidepressants and who are prepared to tolerate the side effects and dietary restrictions associated with its use. See guidance notes above for further information on tyramine-rich foods.
  2. Consider its toxicity in overdose when prescribing for patients at high-risk of suicide.
  3. June 2020: Supplies of licensed phenelzine tablets (Nardil) will be unavailable for the foreseeable future, and supplies of unlicensed phenelzine tablets are reported to be unreliable (DHSC June 2020). No new patients should be initiated on phenelzine.
    • GPs should identify all patients prescribed phenelzine 15mg tablets and;
      • refer these patients for a specialist mental health review regarding ongoing management (for DPT patients, use the standard DPT referral process for single point of access, e-mail dpt.spa@nhs.net or telephone 0300 555 5000 (option 1, option 3); and
      • ensure patients have a sufficient supply until their review, to avoid abrupt withdrawal. It may be necessary to prescribe phenelzine 15mg capsule specials if a further supply of phenelzine is required (please see here)
    • It is clinically unsafe to stop or switch phenelzine abruptly, therefore, any switching or withdrawal will need to be undertaken by a specialist

Reversible inhibitor of monoamine-oxidase type A (RIMA)

Moclobemide
  • Tablets 150mg, 300mg (£20.63 = 150mg daily)

Indications and dose

  • Depression: initially 300mg daily usually in divided doses after food, adjusted according to response; usual range 150–600mg daily
  • Social anxiety disorder: initially 300mg daily increased on fourth day to 600mg daily in 2 divided doses, continued for 8–12 weeks to assess efficacy

Notes

  1. Moclobemide is claimed to cause less potentiation of the pressor effect of tyramine than the traditional (irreversible) MAOIs, but patients should avoid consuming large amounts of tyramine-rich foods. See guidance notes above for further information.

 

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