Monoamine oxidase inhibitors (MAOIs) for depression
Monoamine oxidase inhibitors (MAOIs) were some of the first antidepressants to be developed. These days, MAOIs are not frequently prescribed as initial treatment for depression because of their potential for serious side effects and interactions with other medicines and certain foods. However, they can be useful in treating depression in some cases when other medicines have been ineffective.
MAOIs used in Australia are phenelzine (brand name Nardil) and tranylcypromine (brand name Parnate).
How they work
Depression is believed to be associated with low levels of chemicals that are involved with transmitting signals between nerve cells in the brain. The MAOI antidepressants work by stopping the breakdown of these chemicals so that more of them stay in the brain helping to transmit the signals. This is a slightly different action to tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs).
MAOIs are often not the first choice of antidepressant because they are associated with many side effects. Some of these side effects include:
- low blood pressure;
- dry mouth;
- insomnia or lethargy;
- blurred vision;
- sexual problems;
- rapid heartbeat; and
Diet and MAOIs
The most important aspect your doctor will consider when deciding to prescribe a MAOI is the need for people taking these medicines to follow a strict diet while taking them. The reason why this is necessary is because MAOIs react with an amino acid known as tyramine, which is found in many popular foods and alcoholic beverages. The effect is that tyramine levels rise in the brain and this can cause sudden and significant elevations in blood pressure.
Some of the food and drinks that should be avoided while taking MAOIs include:
- matured cheeses;
- certain meats (e.g. salami);
- Vegemite and other concentrated yeast extracts;
- soy sauce;
- banana skins;
- broad bean pods;
- tap and home-brewed beers; and
- Chianti wine.
So, if you consume any of these foods while taking a MAOI, your blood pressure may rise rapidly and you may get severe symptoms such as headache, nausea, vomiting, or a fast heartbeat. Such a situation is a medical emergency and can be very dangerous if not treated properly. If you have a reaction after eating any of these foods, contact a doctor or hospital immediately.
MAOIs and other medicines
MAOIs interact with many other medicines, so you must always check with your doctor or pharmacist before taking any other medicines, including non-prescription and complementary medicines.
You should not take preparations containing pseudoephedrine (found in many cough and cold preparations that you can buy over the counter in a pharmacy or supermarket) or any similar medicines while you are taking MAOIs.
A variety of other prescription medicines should also be avoided if you are taking MAOIs, including other antidepressants, opiates, certain asthma medicines and medicines to treat high blood pressure.
MAOIs also interact with many illicit drugs.
Your doctor or pharmacist should give you a list of all foods, drinks and medicines to avoid, and you should follow this list to the letter. Even after you stop taking MAOIs, you need to continue to avoid these foods and medicines for at least 14 days, as there is still a possibility of interactions during this period.
Reversible inhibitors of monoamine oxidase (RIMAs)
There is another class of medicine that is similar to MAOIs – reversible inhibitors of monoamine oxidase (RIMAs). Moclobemide (e.g. Aurorix, Amira) is the only medicine in this class available in Australia.
Moclobemide is not subject to as many of the dietary restrictions as the MAOIs when taken in recommended doses. Moclobemide is used to treat major depression. It can help with symptoms of sleeping difficulties and inability to concentrate, and is generally well tolerated by people. It is often prescribed as an alternative to SSRIs.
How they work
Like the MAOIs, moclobemide works on brain chemicals, but it is more targeted. It doesn’t inhibit one of the chemicals that breaks down tyramine, so the tyramine still gets broken down and doesn’t build up dangerously in the brain to cause high blood pressure. This means that people taking moclobemide can generally still eat foods containing tyramine and that it is more likely that their body will break it down. To be doubly sure, moclobemide is usually taken after food. However, people taking moclobemide should still avoid cough and cold preparations that contain pseudoephedrine, and it is still prudent to check with your doctor or pharmacist before starting new prescribed or over the counter medicines.
Side effects, including difficulty sleeping, dizziness, nausea and headache, usually go away after a while.
2. Moclobemide (revised October 2008). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2012 Nov. http://online.tg.org.au/complete/ (accessed Dec 2012).
3. MayoClinic.com. Monoamine oxidase inhibitors (MAOIs) (updated 8 Dec 2010). http://www.mayoclinic.com/health/maois/MH00072 (accessed Dec 2012).