Monoamine Oxidase Inhibitors
Monoamine oxidase inhibitors (MAOIs) were among the first antidepressants to be discovered. They work by slowing down the action of monoamine oxidase, an enzyme that helps break down chemical messengers (neurotransmitters, including serotonin, norepinephrine and dopamine). By stalling this process, MAOIs increase the availability of chemical messengers, modifying nerve pathways that control mood. MAOIs are as effective as any other antidepressant, but you must avoid certain foods and drugs (see below). Because of this inconvenience, MAOIs are prescribed relatively infrequently.
One reason MAOIs are still used is that they work differently from other antidepressants, so they may work when other drugs do not. MAOIs are also effective for treating panic and other anxiety disorders.
MAOIs may be taken two or three times per day, with or without food. Older adults generally take lower doses.
MAOIs are associated with the following side effects. Always report any new symptoms to your doctor, whether they are on this list or not:
- Severe headache, rapid heartbeat, chest pain, sweating, nausea, vomiting and/or a stiff neck may be signs of DANGEROUSLY HIGH BLOOD PRESSURE, which is a medical emergency. If you follow the special diet, however, the risk of a blood-pressure crisis is very low.
- Dizziness, lightheadedness or fainting, especially if you stand up suddenly from a sitting or lying position. This problem is especially common in older adults.
- Leg swelling
- Nervousness, restlessness or tremulousness
- Mild headaches
- Weight gain, increased cravings for sweets
- Trouble sleeping, muscle twitching during sleep
While taking MAOIs, you must follow a strict diet. The enzyme blocked by MAOIs also helps to break down tyramine, a substance found in some foods. High levels of tyramine can cause a quick and dangerous rise in blood pressure. So, if you take MAOIs, you must avoid foods with tyramine. Some aged, ripened or fermented foods have too much tyramine in them, including:
- Aged cheese
- Fava beans or broad bean pods
- Yeast or meat extracts
- Smoked or pickled meat, poultry or fish
- Fermented meats, such as bologna, pepperoni and salami
- Miso soup
- Overripe fruit
- Many alcoholic beverages, especially red wine, sherry, beer and ale
- Products that contain caffeine, including coffee, tea, cola and chocolate
Some drugs can interact with MAOIs and should be avoided completely. Other drugs can be taken under the close supervision of your doctor.
Tell your doctor about any drugs you are taking, especially:
- Stimulants, such as amphetamines, methylphenidate (Ritalin), some cold medicines and diet pills
- Blood-pressure drugs
- Other antidepressants, especially selective serotonin reuptake inhibitors such as fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil) or citalopram (Celexa)
- Asthma drugs
- Pain relievers, such as meperidine (Demerol)
- Drugs for diabetes, including insulin
- Tryptophan (taken as a food supplement or as a sleep aid)
Cocaine can be deadly on its own. When combined with MAOIs, it can cause dangerously high blood pressure.
Suicide Risk. All antidepressants carry warnings about suicide. In October 2004, the Food and Drug Administration began requiring that manufacturers include a warning on package inserts for all antidepressants. The warning mentions the risk of suicidal thoughts, hostility and agitation in both children and adults.
After you start taking any antidepressant, there is a risk that you may feel worse rather than better. The danger is greatest in the first few weeks of treatment, so make sure you follow-up with your doctor. There is also a small risk for an increase in suicidal thinking and behavior. Fortunately, some research shows that the overall suicide rate decreases in people taking antidepressants. However, a small number of people using antidepressants do encounter a lower mood, and feel more anxious, irritable, self-destructive or impulsive.
Stopping your MAOIs. Because MAOIs have a stimulant effect, you may become depressed, anxious, agitated, sleepless or drowsy when you stop taking them, just as you would as if you stopped taking a stimulant drug. In addition, you may develop psychosis, which is distorted thinking such as hallucinations (false perceptions) or delusions (false ideas). This problem can usually be avoided if you decrease your dose slowly before stopping it.
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