Phenelzine Norepinephrine

There are currently three approved MAOis in the United States phenelzine (Nardil), tranylcypromine (Parnate), and isocarboxizide (Marplan). These medications are all nonselective, irreversible inhibitors of the MAO enzymes. Being irreversible, the MAOis permanently deactivate the MAO enzyme molecule when they bind it, and being nonselective, they block the actions of both the MAO-A and MAO-B enzyme subtypes. By deactivating the MAO-A enzyme, MAOis increase the activity of both norepinephrine and serotonin. Blocking the MAO-B enzyme adds little to their effectiveness but causes many problematic side effects. 

Side effects, mainly due to serotonin reuptake inhibition include G1 upset, nervousness, and sexual dysfunction. SSRls are associated with an increased risk of falls. Hyponatraemia due to SIADH is an uncommon, but important side effect in elderly patients. Selective serotonin and norepinephrine reuptake inhibitors (S SNRls) such as venlafaxine and duloxetine are also useful in older patients. Other heterocyclic antidepressants of importance in older patients because of relative safety include bupro-prion and mirtazepine. They are reserved for patients with resistance to or intolerance of SSRls. Currently, trazodone is used mostly for sleep disturbance in depression in doses of 50-100 mg at bedtime. The monoamine oxidase inhibitors phenelzine. 

Monoamine oxidase inhibitors. The monoamine oxidase inhibitors (MAOIs) inhibit the intracellular catabolic enzyme monoamine oxidase. There are two types of monoamine oxidase MAO-A and MAO-B, both of which metabolize tyramine and dopamine. In addition, MAO-A preferentially metabolizes norepinephrine, epinephrine, and serotonin, and MAO-B preferentially metabolizes phenylethylamine (an endogenous amphetamine-like substance) and N-methylhistamine (Ernst, 1996). Some MAOIs are selective for A or B and some are nonselective (mixed). In addition, irreversible MAOIs (e.g., phenelzine, tranylcypromine) are more susceptible to the cheese effect than are the reversible agents (e.g., moclobemide). 

The enzyme, monoamine oxidase, exists in two forms MAO-A (intestinal mucosa and intraneuronally in the brain) and MAO-B (platelets and mainly extraneuronally in the brain). Serotonin is preferentially metabolised by MAO-A and noradrenaline (NA norepinephrine), and dopamine and lyramine by both forms. The first generation MAOI antidepressants (phenelzine, tranylcypromine, and isocarboxazid) inhibit both MAO-A and MAO-B and are thought to work by increasing the availability of 5-HT and NA in the synapse—with longer-term adaptive effects occurring as for the TCAs. These MAOls are irreversible, i.e. they permanently inactivate MAO. Thus, recovery of activity occurs slowly, over days, as new MAO molecules are synthesised. 

Correct answer = D. Carbidopa inhibits the peripheral decarboxylation of levodopa, permitting lower dosage. Chlorpromazine blocks the dopamine receptor site in the brain and therefore blocks the beneficial effects of levodopa. Vitamin B6 enhances the peripheral decarboxylation of levodopa. Dopamine does not itself cross the blood-brain barrier. Phenelzine inhibits the metabolism of norepinephrine and serotonin and may produce a hypertensive crisis. 

Monoamine oxidase (MAO) is a mitochondrial enzyme found in neural and other tissues, such as the gut and liver. In the neuron, MAO functions as a safety valve to oxidatively deaminate and inactivate any excess neurotransmitter molecules (norepinephrine, dopamine, and serotonin) that may leak out of synaptic vesicles when the neuron is at rest. The MAO inhibitors may irreversibly or reversibly inactivate the enzyme, permitting neurotransmitter molecules to escape degradation and therefore to both accumulate within the presynaptic neuron and to leak into the synaptic space. This causes activation of norepinephrine and serotonin receptors, and may be responsible for the antidepressant action of these drugs. Three MAO inhibitors are currently available for treatment of depression phenelzine [FEN el zeen], isocarboxazid [eye soe kar BOX a zid], and tranylcypromine [tran ill SIP roe meen] no one drug is a prototype. Use of MAO inhibitors is now limited because of the complicated dietary restrictions required of patients taking MAO inhibitors. 

MDMA MAOIs Risk of severe and life-threatening hypertension. Risk is greatest with non-selective MAOIs. At least four deaths have been reported following the ingestion of MDMA and modobemide. Another death was reported after phenelzine co-ingestion MAO is an enzyme that metabolizes dopamine, norepinephrine and other amines Avoid concurrent use... 

Monoamine oxidase inhibitors (MAOI) Neurotransmitters norepinephrine, dopamine, epinephrine, and serotonin are inactive by the enzyme monoamine oxidase. MAOI inhibits monoamine oxidase, resulting in a rise in the levels of these neurotransmitters. MAOI are isocarboxazid (Marplan), phenelzine sulfate (Nardil), and tranylcypromine sulfate (Parnate). 

Monoamine oxidase inhibitors Phenelzine Selective norepinephrine re-uptake Reboxetine... 

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