University:
University of North Carolina at Chapel Hill
Course:
NURS 312 | Pharmacology
Academic year:

2020
Views:

263

Pages:

1
Author:

Prince Sampson

3.3 – “Of Mice & MAOIs” Physiology • Monoamine oxidases (MAO) breaks down monoamines (serotonin, NE, dopamine) (MAO = mouse). Two forms: o MAO-A deaminates dopamine, serotonin, and norepinephrine (albino mouse nibbling from smiley-faced & compass cheeses as well as dopamine rope). Usually breaks down tyramine in the GI tract (albino mouse eating meat) o MAO-B preferentially metabolizes deaminates dopamine (black mouse eating rope) • MAO-inhibitors (MAOIs) (mousetraps) o Include tranylcypromine (“Try a sip of wine!”), phenelzine (funnel in bottle), isocarboxazid (boxed wine) o Selegeline is a selective MAO-B inhibitor(sledgehammer hitting black mouse) ▪ inhibits breakdown of dopamine, increasing CNS levels. Useful in management of motor SSx of Parkinson’s as adjunct therapy to levodopa (cogwheeled clock). Especially useful with fluctuating or decreasing response to levodopa. o Block monoamine oxidase, decreasing breakdown of monoamines and thereby increasing their availability & increasing serotonin, NE, & dopamine transmission in CNS & periphery, enhancing activity of all of these. Irreversible (dead rat). o Historically used for depression & anxiety, but out of favor d/t adverse effects (comedy/tragedy masks) ▪ Not first line. Like TCAs, have potential lethal OD, require careful titration, many drug interactions & many adverse effects. Reserved for treatment resistant depression (bottle resistant to opening). ▪ May be useful in treating atypical depression with traits like hyperphagia, hypersomnia, leaden paralysis. o Adverse effects ▪ Most common are orthostatic hypotension, weight gain, & decreased sexual function; • Most severe sexual dysfunction effects of any antidepressant. ▪ Should be avoided with tyramine containing food (aged meats, wine, cheese). Without MAO-A activity, tyramine enterers circulation & acts as a sympathomimetic (Falling norepinephrine cheeses). May lead to tyramine toxicity, which can precipitate a hypertensive crisis. ▪ Chronic use of tyramine + MAOIs may cause malignant HTN ▪ Associated with serotonin syndrome (pile of smiley-face cheeses). Most serotonergic antidepressants should be discontinued at least 2 weeks before beginning an MAOI.