Sketchy Pharm: MAO Inhibitors

Question 1

Describe the basic working of monoamine oxidase inhibitors.

Answer 1

Monoamine oxidase degrades dopamine, norepinephrine, and serotonin, so inhibiting it increases its availability.

Question 2

Explain the differences between MAO-A and MAO-B.

Answer 2

MAO-A deaminates dopamine, norepinephrine, and serotonin (albino mouse eating smiley face, dope rope, and north compass), while MAO-B deaminates only dopamine.

Question 3

True or false: most MAO inhibitors are nonselective and irreversible.

Answer 3

True! Think of the mouse trap (which represents MAOIs) –it doesn’t care what color the mouse is and its effects can’t be undone.

Question 4

What are the three MAOIs we need to know for Step 1?

Answer 4

Tranylcypramine (TRy a SIP of wINE), isocarboxazid (boxed wine), and phenylzine (funnels-in wine)

Question 5

What MAOI might be given to someone with Parkinson’s and why?

Answer 5

Selegiline (the guy with the sledge hammer) because it is a MAO-B selective inhibitor, and thus raises levels of available of dopamine. (Recall also in this sketch that this helps with the “cogwheel rigidity” of Parkinson’s, as depicted on the wall behind the man with the sledge hammer.)

Question 6

What foods can contain toxic levels of tyramine?

Answer 6

Aged wine, cheese, and meat

Question 7

Your uncle just went to France and ate a lot of wine and cheese and calls you saying that he has palpitations and is sweating excessively. What medications might you ask him about?

Answer 7

Tranylcypramine, phenylzine, or isocarboxazid. If he’s taking MAOIs, then have him get phentolamine to treat the potentially fatal hypertension that can come with excess catecholamines.

Aged foods contain tyramine, which is normally broken down by MAO in the gut. If you’re taking a MAOI, however, then that won’t be broken down and can thus build up.