Monoamine Oxidase Inhibitors (MAOIs)
- Nardil (generic name: phenelzine), starting dose 15 mg/day, maximum dosage 60 mg/day
- Parnate (generic name: tranylcypromine), starting dose 30 mg/day, maximum dosage 60 mg/day
Serotonin, norepinephrine, and dopamine are three types of neurotransmitters that send messages to the brain about body activity. When these neurotransmitters have sent their messages, they get "burned up" by a brain protein known as monoamine oxidase, an enzyme found only in the brain and the liver. Depression has been linked to low levels of monoamines; the brain may use up too much of this protein, which may contribute to depressed mood levels. Monoamine oxidase also works to regulate another molecule, tyramine, which affects blood pressure. Tyramine is found naturally in foods like aged cheese, chicken liver, sour cream, raspberries, chocolate, yogurt, and broad-bean pods. The tyramine in these foods can cause increased blood pressure, severe headaches, and migraine in some people.
Antidepressants known as monoamine oxidase inhibitors, or MAOIs for short, work by blocking the protein-destroying activity of monoamine oxidase, leaving higher levels of the protein in the brain. This is thought to help decrease depressive mood. However, the blockage of monoamine oxidase also causes a rise in the level of tyramine in the blood, which can be a serious side effect. High levels of tyramine can cause a sudden, fatal increase in blood pressure, and can even raise the blood pressure so high that blood vessels in the brain can burst, causing aneurysm.
Early MAOI medications were considered dangerous because they can also seriously damage the liver and cardiovascular system. When MAOIs were first introduced in the United States in the 1960s, a wave of deaths from brain hemorrhages took them off the market for a time. Newer versions of MAOIs considered safer have been introduced into the market, but they are very often considered the anti-depressant of last resort, because they are only advised in a limited number of people. Most patients put on MAOIs must also follow a very strict diet in which tyramine-containing foods are prohibited to avoid the possible onrush of tyramine in their systems.
People who suffer from any of the following conditions should not take MAOIs:
- serious heart problems
- epilepsy
- bronchitis
- asthma
- high blood pressure
MAOIs have a long list of potential side effects. If you are experiencing any of these symptoms while taking an MAOI, you should contact your medical doctor immediately:
- Unusually high blood pressure
- Fast or slow heartbeat
- Severe headache
- Increased sweating
- Increased sensitivity to light
- Severe chest pain
- Stiff or sore neck
- Severe dizziness or lightheadedness, especially when arising from a sitting or lying position
- Pounding heartbeat
- Fever
- Slurred speech
- Staggering walk
- Diarrhea
- Swelling of feet and/or lower legs
- Unusual excitement or nervousness
- Dark urine
- Skin rash
- Sore throat
- Yellow eyes and/or skin
Most importantly, MAOIs can cause serious and often fatal side effects if combined with other prescription and over-the-counter medications. These side effects include nausea, vomiting, rapid heartbeat, high blood pressure, rigidity, shock, and mental disturbances. The most dangerous drugs that should never be taken with MAOIs are any selective serotonin reuptake inhibitors (SSRIs), over-the-counter flu and cold remedies containing decongestants, asthma inhalants, weight-control medications and over-the-counter appetite suppressants. Most of these medications contain stimulants that can raise blood pressure, increasing the danger of aneurysm or cardiac arrest.
Source: Carol Turkington and Eliot F. Kaplan, MD, "Making the Antidepressant Decision," Contemporary Books/McGraw-Hill Companies, 2001.
