Antidepressants (cont.)

Combining MAOIs with drugs that increase serotonin may cause:

Combining MAOIs with norepinephrine or drugs that constrict blood vessels (epinephrine, amphetamines, pseudoephedrine, ephedrine, phenylpropanolamine, and phenylephrine) may increase blood pressure to dangerous levels.

The antibiotic linezolid (Zyvox) and intravenous methylene blue should not be combined with MAOIs because they also inhibits monoamine oxidase.

MAOIs should be discontinued at least two weeks before administration of drugs that interact with MAOIs. Drugs that interact with MAOIs should be discontinued at least 1-2 weeks before administration of MAOIs. Because the effect of fluoxetine lasts for several weeks after discontinuation, MAOIs should not be initiated for at least five weeks after stopping fluoxetine.

MAOIs are associated with headache and insomnia which may decrease with continued use. Headaches may require treatment with nonsteroidal antiinflammatory drugs (for example, ibuprofen), and insomnia may require treatment with benzodiazepines [for example, diazepam (Valium) or other drugs for insomnia.

Because MAOIs stimulate the nervous system, they may be beneficial for depressed patients who over-sleep or are fatigued.

Hypertension may occur during therapy with MAOIs. Therefore, blood pressure should be monitored periodically during MAOI treatment. Hypertensive crisis may occur when MAOIs are combined with tyramine containing foods or drugs that constrict blood vessels.

Symptoms of hypertensive crises include:

Bleeding in the brain also may occur. Patients should be aware of signs and symptoms of hypertensive crisis and should seek immediate medical treatment if these signs or symptoms are present. Hypertensive crisis may be managed with nitroprusside (Nitropress), labetalol (Normodyne, Trandate), or phentolamine.

Orthostatic hypotension (feeling faint upon standing due to decreased blood flow to the brain) also occurs. Patients should rise slowly from a sitting position to reduce the effect of orthostatic hypotension. Orthostatic hypotension may be treated with steroids.

Some patients may experience peripheral edema (swelling of the lower legs and ankles) which can be improved by wearing support stockings.

Weight gain also occurs during MAOI therapy, and tranylcypromine (Parnate) causes more weight gain than other MAOIs. MAOIs also are associated with sexual side effects such as decreased sexual drive, erectile dysfunction, difficulty ejaculating or reaching orgasm. Sexual side effects may diminish with time or a reduction in dose.

What are examples of MAOIs?

  • phenelzine (Nardil)
  • tranylcypromine (Parnate)
  • isocarboxazid (Marplan)
  • selegiline transdermal system (EMSAM)

What are tricyclic antidepressants (TCAs)?

TCAs have been in use since the 1950s when imipramine (Tofranil) was shown to be effective for treating depression. TCAs primarily work by increasing the level of norepinephrine in the brain and to a lesser extent serotonin levels. Some TCAs also are antihistamines (block the action of histamine) or anticholinergic (block the action of acetylcholine, a neurotransmitter), and these additional actions allow for uses of TCAs other than for treating depression as well as additional side effects.



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