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CNS - Depression & Bipolar - INTRO - MAOIs

34 important questions on CNS - Depression & Bipolar - INTRO - MAOIs

What are some adverse effects listed?

Nausea
Dizziness
Headache
Insomnia
Rarely excitement
Liver damage

What is moclobemide and its action duration?

Moclobemide is a reversible and selective MAO-A inhibitor with short duration of action. Full MAO activity is restored within 1–2 days of stopping the drug.

What has moclobemide emerged as?

Moclobemide has emerged as a well tolerated alternative to TCAs for mild to moderate depression and for social phobia.

What is MAO and what is its role?

MAO is a mitochondrial enzyme involved in the oxidative deamination of biogenic amines (Adr, NA, DA, 5-HT). It plays a crucial role in neurotransmitter metabolism.

How does moclobemide compare to TCAs in clinical trials?

Clinical trials have shown moclobemide to be an efficacious antidepressant, comparable to TCAs, except in severe cases. It lacks the adverse effects of typical TCAs and is safer in overdose.

What does selegiline selectively inhibit and at what doses?

Selegiline selectively inhibits MAO-B at lower doses (5–10 mg/day), but not effective in depression.

What are the frequently reported adverse effects of Moclobemide?

Frequently reported adverse effects of Moclobemide include:

Nausea
Headache
Dizziness
Insomnia
Agitation

How many isoenzyme forms of MAO have been identified?

Two isoenzyme forms of MAO have been identified. They are MAO-A and MAO-B, each with specific substrates and inhibitors.

Why is moclobemide a good option for elderly patients?

Moclobemide is a good option for elderly patients and those with heart disease because it lacks the anticholinergic, sedative, cognitive, psychomotor, and cardiovascular adverse effects of typical TCAs.

What type of enzyme inhibitor is Moclobemide?

Moclobemide is a reversible inhibitor of monoamine oxidase A (RIMA) enzyme. It competitively and reversibly inhibits monoamine oxidase (MAO). It is relatively selective for type A.

With which substances should Moclobemide not be prescribed?

Moclobemide should not be prescribed with:

Pethidine
Selegiline
Psychostimulants
Sympathomimetic amines

What does MAO-A preferentially deaminate and what inhibits it?

MAO-A preferentially deaminates 5-HT and NA, and is inhibited by clorgyline and moclobemide. It plays a role in neurotransmitter regulation.

What is the recommended dose and some brands of moclobemide?

The dose for moclobemide is 150 mg BD–TDS (max 600 mg/day). Brands include RIMAREX, TRIMA 150, 300 mg tabs.

What are the symptoms of an acute attack of HBP/Hypertensive crisis due to MAOIs?

Symptoms include:

Severe headache
Nausea and vomiting
Sweating and severe anxiety
Nose bleeds
Tachycardia
Chest pain
Dyspnea
Confusion
Disturbance in vision

What does MAO-A selectively degrade?

MAO-A selectively degrades serotonin, noradrenaline, and dopamine. Moclobemide inhibits MAO-A even in the gut. It does not interact with sympathomimetic agents and tyramine-containing foods.

Is a tyramine-free diet required when taking Moclobemide?

A tyramine-free diet is generally not required and the risk is further minimized by ingesting Moclobemide after meals.

What does MAO-B preferentially deaminate and what inhibits it?

MAO-B preferentially deaminates phenylethylamine and is inhibited by selegiline. It is involved in the breakdown of specific neurotransmitters.

What do both MAOs A & B metabolize?

Both MAOs A & B metabolize tyramine and dopamine.

How is tyramine metabolized, and what is Moclobemide's interaction with it?

Tyramine is metabolized by monoamine type B (MOA-B). Moclobemide does not interact with sympathomimetic agents and tyramine-containing foods.

What are the cardiovascular effects and lethality of Moclobemide in overdose?

Moclobemide is free of cardiovascular adverse effects and has a low lethality in overdose.

Does Moclobemide interact with alcohol?

There is no interaction with alcohol when taking Moclobemide.

What is the "cheese effect" in the context of irreversible MAOIs?

The "cheese effect" is a rise in blood pressure due to the sudden release of noradrenaline from peripheral sympathetic terminals, caused by displacement from vesicles by tyramine due to MAO inhibition.

What is the likelihood of reversible inhibitors of monoamine oxidase-A interacting with dietary amines at therapeutic doses?

At therapeutic doses, they are unlikely to interact with dietary amines.

What are amines classified as in the context of irreversible MAOIs?

Amines are any member of a family of containing N organic compounds classified as prim, seco, tert, and quaternary based group attached, e.g., catecholamines.

Describe the selectivity and affinity of Moclobemide for MAO-A.

Moclobemide has a high selectivity and affinity for MAO-A.

What role does tyramine play in the "cheese effect"?

Tyramine is a natural amine and catecholamine releasing agent that does not cross the BBB, exerting non-psychoactive peripheral sympathomimetic effects, known as the "cheese effect."

What do irreversible Monoamine oxidase inhibitors (MAOIs) inhibit?

These inhibitors irreversibly inhibit Monoamine metabolism (MAOIs A and B). They include phenelzine, tranylcypromine, isocarboxazid, and pargyline. They interact with dietary monoamine causing the "cheese effect."

How are amines metabolized according to the information on irreversible MAOIs?

Amines are metabolized by MAO-A (noradrenaline and 5HT3) or MAO-B (dopamine e.g., Selegiline used for parkinsonism).

What is a surprising side effect of irreversible MAOIs related to dopamine?

Surprisingly, Orthostatic hypotension occurs due to the accumulation of dopamine in the sympathetic cervical ganglia, where it acts as an inhibitory transmitter.

How do RIMAs differ from MAOIs in terms of enzyme inhibition?

Unlike the MAOIs, the RIMAs are reversible inhibitors of the enzyme and can easily be displaced from the enzyme surface by any primary amine present in the diet.

Why is Iproniazid no longer used?

Iproniazid is no longer used due to hepatotoxicity. It was the first effective antidepressant discovered before the discovery of imipramine.

What is the main limitation to the clinical use of MAOIs?

Main limitation to the clinical use of the MAOIs is due to their interaction with amine-containing foods such as cheeses, red wine, beers, fermented and processed meat products, yeast products, soya, and some vegetables.

What is the mechanism of action for all MAOIs?

All MAOIs have a similar mechanism of action: inhibit the intra- and interneuronal metabolism of the biogenic amine neurotransmitters (noradrenaline, dopamine, and serotonin).

Which medicines interact with MAOIs?

Medicines containing sympathomimetics, e.g., ephedrine, phenylpropanolamine interact with MAOIs.

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Phamarcology

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