Monoamine oxidase inhibitors

Monoamine oxidase inhibitors (MAO inhibitors) are a type of antidepressant used to treat mental depression. Like other antidepressant drugs, MAO inhibitors help reduce the extreme sadness, hopelessness, and lack of interest in lifethat are typical in people with depression. MAO inhibitors are especially useful in treating people whose depression is combined with other problems suchas anxiety, panic attacks, phobias, or the desire to sleep too much.

Discovered in the 1950s, MAO inhibitors work by correcting chemical imbalances in the brain. Normally, natural chemicals called neurotransmitters carry signals from one brain cell to another. Some neurotransmitters, such as serotonin and norepinephrine, play important roles in controlling mood. But other substances in the brain may interfere with mood control by breaking down theseneurotransmitters. Researchers believe that MAO inhibitors work by blocking the chemicals that break down serotonin and norepinephrine. This gives the neurotransmitters more time to do their important work.

Because MAO inhibitors also affect other chemicals throughout the body, thesedrugs may produce many unwanted side effects. They can be especially dangerous when taken with certain foods, beverages and medicines. Anyone taking these drugs should ask his or her physician or pharmacist for a list of productsto avoid.

MAO inhibitors are available only with a physician's prescription and are sold in tablet form. Some commonly used MAO inhibitors are isocarboxazid (Marplan), phenelzine (Nardil), and tranylcypromine (Parnate). The recommended dosage depends on the type of MAO inhibitor and the type of depression for which it is being taken.

MAO inhibitors can cause serious and possibly life-threatening reactions, such as sudden hypertension, when taken with certain foods, beverages, ormedicines. The dangerous reactions may not begin until several hours after consuming these things. Aged cheeses, red wines, smoked or pickled meats, chocolate, caffeinated beverages, and foods containing monosodium glutamate (MSG)are among the foods and drinks to be avoided.

People who take MAO inhibitors should not drink alcoholic beverages or use any other medicine unless it has been approved or prescribed by a physician whoknows that they are taking MAO inhibitors. This includes nonprescription (over-the-counter) medicines such as sleep aids; medicines for colds, cough, hayfever, or asthma (including nose drops or sprays); medicines to increase alertness or keep from falling asleep; and appetite control products.

Because MAO inhibitors work on the central nervous system, they may add to the effects of alcohol and other drugs that slow down the central nervous system, such as antihistamines, cold medicine, allergy medicine, sleep aids, medicine for seizures, tranquilizers, some pain relievers, and muscle relaxants.

MAO inhibitors may also interact with medicines used during surgery, dental procedures, or emergency treatment. These interactions could increase the chance of side effects.

Some people feel drowsy, dizzy, lightheaded, or less alert when using MAO inhibitors. The drugs may also cause blurred vision. For these reasons, anyone who takes these drugs should not drive, use machines or do anything else thatmight be dangerous until they have found out how the drugs affect them. Olderpeople may be especially sensitive to the side effects of MAO inhibitors, especially dizziness or lightheadedness.

Anyone who has had unusual reactions to MAO inhibitors in the past should lethis or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

Studies suggest that taking MAO inhibitors during pregnancy may increase therisk of birth defects or problems in the newborn after birth. MAO inhibitorsmay pass into breast milk, but no problems have been reported in nursing babies whose mothers took the medicine.

MAO inhibitors may also affect blood sugar levels, and diabetics who take them must be cautious. Before using MAO inhibitors, people with any of these medical problems should make sure their physicians are aware of their conditions:

  • Alcohol abuse
  • High blood pressure
  • Recent heart attack or stroke
  • Heart or blood vessel disease
  • Liver disease
  • Kidney disease
  • Frequent or severe headaches
  • Epilepsy
  • Parkinson's disease
  • Current or past mental illness
  • Asthma or bronchitis
  • Overactive thyroid
  • Pheochromocytoma(a tumor of the adrenal gland).

Taking MAO inhibitors with certain other drugs may affect the way the drugs work or may increase the chance of side effects. The most common side effectsare dizziness, lightheadedness, drowsiness, tiredness, weakness, blurred vision, shakiness or trembling, restlessness, sleep problems or twitching duringsleep, increased appetite (especially for sweets), weight gain, decreased sexual ability, decreased amount of urine, and mild headache. These problems usually go away as the body adjusts to the drug and do not require medical treatment unless they interfere with normal activities.

More serious side effects may include:

  • Severe chest pain
  • Severe headache
  • Stiff, sore neck
  • Enlarged pupils
  • Increased sensitivity of eyes to light
  • Fast or slow heartbeat
  • Sweating, with or without fever or cold, clammy skin
  • Nausea and vomiting.

Anyone who takes MAO inhibitors must check with his or her physician before taking any other prescription or nonprescription (over-the-counter) medicine. Among the drugs that may interact with MAO inhibitors are:

  • Central nervous system (CNS) depressants such as medicine for allergies, colds, hay fever, and asthma; sedatives; tranquilizers; prescription pain medicine; muscle relaxants; medicine for seizures; sleep aids; barbiturates; and anesthetics.
  • Medicine for high blood pressure
  • Other antidepressants, including tricyclic antidepressants (such as Tofranil and Norpramin), antidepressants that raise serotonin levels (such as Prozac and Zoloft), and bupropion (Wellbutrin)
  • Diabetes medicines taken by mouth
  • Insulin
  • Water pills (diuretics).

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