Final answer:
Imipramine is a tricyclic antidepressant that is less potent than its metabolite, desipramine, which is more effective at inhibiting norepinephrine reuptake in the brain. MAOIs like phenelzine and tranylcypromine inhibit monoamine oxidase, leading to increased neurotransmitter levels. However, they are less commonly used due to significant risks and interactions.
Step-by-step explanation:
Imipramine is less potent than its metabolite, desipramine. Both drugs are tricyclic antidepressants, which work by inhibiting the uptake of neurotransmitters like serotonin and norepinephrine in the brain, thereby increasing their levels. Imipramine undergoes first-pass metabolism and is converted to desipramine, which is a more potent inhibitor of norepinephrine reuptake, leading to its greater antidepressant effect. Unlike imipramine, desipramine has a preferential action on norepinephrine reuptake without affecting serotonin uptake as significantly.
In the class of monoamine oxidase inhibitors (MAOIs), examples include iproniazid (discontinued), phenelzine (Nardil), isocarboxazid (Marplan), tranylcypromine (Parnate), selegiline (Emsam), and moclobemide (Aurorix/Amira). These drugs inhibit the monoamine oxidase enzyme, thus preventing the breakdown of neurotransmitters in the brain, which can be beneficial for certain psychiatric conditions but are not commonly used due to their toxicity and the risk of potentially lethal food and drug interactions.