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) should not be combined
with MAOIs because linezolid 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.
TCAs may inhibit the antihypertensive effect of
clonidine (Catapres). Therefore, combining TCAs with clonidine may lead to
dangerous elevations in blood pressure.
TCAs may affect the heart's electrical
conduction system. Combining TCAs with drugs that also affect the heart's
conduction system [for example, disopyramide
(Norpace), pimozide (Orap),
procainamide (Pronestyl,
Procan SR, Procanbid)] may
increase the frequency and severity of an abnormal heart rate and rhythm.
Combining TCAs with carbamazepine
(Tegretol) may result in lower TCA blood levels because carbamazepine increases
the break down of TCAs, potentially reducing the effect of TCAs.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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