Monoamine Oxidase Inhibitors (MAOIs) – Antidepressants

00:01 I'm Dr. Shukle. Let's talk about monoamine oxidase inhibitors today.

00:06 The monoamine oxidase inhibitors are drugs that inhibit the breakdown of norepinephrine and serotonin in the presynaptic neuron.

00:17 This allows more of these neurotransmitters in to the synaptic cleft.

00:21 The increase amounts of norepinephrine and serotonin are stored in the vesicles and then they're eventually released when the nerve fires.

00:30 We have several types of monoamine oxidase inhibitors.

00:34 They can be nonselective or selective.

00:37 The nonselective agents are seen here, there's many of them, there's over 20 MAO-A, MAO-B inhibitors.

00:46 We also have selective agents.

00:49 The monoamine oxidase A inhibitors like maclobemide are some of the earliest antidepressants that we've ever used.

00:58 This particular drug was sold commercially as Mannerix.

01:02 Selective monoamine oxidase type B inhibitors include drugs like selegiline.

01:08 These are also commonly used, we see them still being used today.

01:13 Side effects to these medications are usually due to increase amounts of norepinephrine in the nerve terminals themselves, so this can include peripheral autonomic sympathomimetic effects.

01:25 This can lower your blood pressure and it can also increase your risk of seizures by lowering the seizure threshold.

01:36 Finally, we need to discuss the risks of serotonin syndrome inherent to these medications.

01:40 This process is usually occurs on a patient's switches from an SSRI to MAOI.

01:45 If the initial medication is not given adequate time to be eliminated from the body, before starting the new drug, there can be a synergistic effect on serotonin levels.

01:54 Symptoms of high serotonin can include confusion, fevers, vomiting, sweating, and in some cases even seizures.

02:02 This condition can be life threatening so care must be taken to ensure that this medications aren't accidentally combined by a patient or doctor unknowingly, and ensure that patients follow a strict taper schedule when switching their medications.

02:13 Now, what's up with the blood pressure? I just finished saying that there was more norepinephrine in the synaptic cleft.

02:22 If it's sympathomimetic, it should cause more blood pressure and higher blood pressure.

02:26 Well, in the absence of an indirect sympathomimetic, monoamine oxidase inhibitors actually cause a drop in blood pressure, that's a little bit hard to remember.

02:39 In the presence of an indirect sympathomimetic, monoamine oxidase inhibitors cause a rise in blood pressure.

02:47 Monoamine oxidase inhibitors, I'll say MAOIs from now on, may cause severe hypertension in patients taking things like tyramine.

02:56 Tyramine is metabolized by monoamine oxidase.

03:00 Tyramine is found in things like aged-cheeses, soybeans, beers, and red wine, cured and processed meats.

03:11 So, when you're talking about a wonderful Charcuterie board like this, you're talking about a tyramine overload.

03:19 If you have this kind of a picnic, or a romantic dinner and you're on a monoamine oxidase inhibitor, you can run into the risk of having very high blood pressures in the presence of those drugs.