Antidepressants --Monoamine Oxidase (MAO)Inhibitors
Whats the deal with MAO Inhibitors?
Antidepressants are used to treat mood disorders: bipolar disorder and depressive disorders. The MAO inhibitors inhibit the enzyme MAO. This enzyme metabolizes epinephrine, *norepinephrine, and *serotonin. The result is an accumulation of various neurotransmitters (dopamine, epinephrine, norepinephrine, and serotonin), where serotonin deficiencies may be related to depression.
phenelzine / Nardil
Phenelzine is a MAO inhibitor which functions in increasing the levels of serotonin in the brain. This drug is available by mouth (PO) only with the onset beginning at approximately 7-10 days.
tranylcypromine / Parnate
Parnate is a MAO inhibitor, similar to Nardil.
Serotonin is known as a biogenic amine; it has shown to be a mood regulator. Interestingly, the relationship between depression and this disorder was linked during treatment for hypertension. Patients were being treated with a biogenic amine-depleting agent reserpine, and they became depressed. Patients who were being treated for tuberculosis with ipronazid, a biogenic enhancing agent became euphoric.
Serotonin generally serves inhibitory functions in the brain, and disturbances in its functioning may underlie the irritability, anxiety, and sleep disturbances common in depression.
Norephinephrine is also a biogenic amine. Norepinephrine is involved in maintenance of arousal, alertness, and euphoria. Disturbances in norepinephrine function are thought to underlie lack of energy and depressed mood.
Good drug? Bad drug?... Side effects and interactions
There are a number of side-effects and drug interactions with MAO inhibitors. It makes sense if you think about the role that ex. norepinephrine plays in regulation of blood pressure, and heart rate. Consider the role of an anti-hypertensive beta-blocker, where the beta receptors in the myocardium receive norepinephrine and epinephrine. When blocked, the result is a decrease in heart rate, a decrease in contractility thus decreasing cardiac output and peripheral resistance ultimately decreasing blood pressure. Therefore it is logical to consider that MAO inhibits in combination with beta-blockers can cause bradycardia and hypotension.
MAO inhibitors interact with other MAO inhibitors because the risk of hypertension related to the excess of norepinephrine.
MAO inhibitors essentially interact with every kind of drug for one reason for another so it is important to be informed regarding the use of MAO inhibitors with other medications (both Rx and OTC).
Side Effects – the relevant
agitation, sedation, bradycardia, hypertensive crisis, tachycardia, elevated LFT’s, hypernatremia
Monitor cardiovascular status for hypertension, changes in heart rate and palpitations. Keep phentolamine readily available to treat hypertensive crisis without causing excessive hypotension.
Instruct patients with their diet restrictions as some foods contain tyramine or other pressor amines ex. aged cheese; beer; beans; cured meat or sausage; liqueurs; overripe fruit; red and white wine; sauerkraut; sherry; smoked or pickled fish; meats and poultry; year or protein extracts. The effect is an increased risk of sudden hypertension.
Am I hypertensive?
Chest pain? Headache? Neck Stiffness? Palpitations?
Patients: seek immediate medical attention if experiencing any of the signs of a hypertensive episode.