Pirlindole is a selective and reversible inhibitor of monoamine oxidase (MAO) subtype A (MAO-A). It exerts an inhibitory effect on noradrenaline and 5-hydroxytryptamine reuptakes. It has no effect on the dopaminergic and cholinergic systems. It has only a low potential for amplifying tyramine and noradrenaline pressor effect, which makes one expect that it will not be at the basis of a ‘cheese effect’. Pirlindole was approved in some European and non-European countries for the treatment of depression. The antidepressant efficacy and safety of pirlindole have been demonstrated in a number of placebo- and active comparator-controlled studies and are supported by many years of clinical experience in the treatment of depression. The drug's efficacy and safety have also been demonstrated in the treatment of fibromyalgia syndrome. Pirlindole has a favorable tolerability profile, with no deleterious effect on cardiovascular dynamics. The effect of pirlindole on sensorimotor performance relevant to driving a motor vehicle is similar to that of placebo, as pirlindole appears to have an activating rather than a sedating antidepressant profile. Pirlindole prevented qualitative alteration (transformation) in the catalytic activity of membrane-bound type A monoamine oxidases (MAO-A), pathogenetically important for the development of the audiogenic seizures.

Indantadol (previously known as CHF-3381) is an oral and noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist and reversible monoamine oxidase-A (MAO-A) inhibitor that is being developed by Vernalis plc, under license from Chiesi Farmaceutici SpA, for the potential treatment of neuropathic pain. In preclinical studies, indantadol exhibited neuroprotective effects after kainate-induced seizures and displayed anticonvulsant and antihyperalgesic activity. Indantadol also caused a dose-dependent decrease in exploratory motility. In a human heat-capsaicin-induced pain model, indantadol at a dose of 500 mg effectively reduced the area of secondary hyperalgesia. The tolerability profile of the drug at single doses up to 600 mg and twice-daily doses up to 400 mg in clinical trials was significantly more favorable than for other NMDA antagonists. Most side effects have been observed to be mild, and include dizziness and asthenia. Indantadol was in phase II clinical trials for the treatment of chronic cough and neuropathic pain. However, these studies had been discontinued.

Clorgiline is a monoamine oxidase (MAO) inhibitor. Specifically, it is an irreversible and selective inhibitor of MAO-A. Clorgiline was under investigation for antidepressant and anxiolytic potential but has never been marketed, likely due to efficacy concerns. It continues to see routine use as a molecular probe in biomedical research examining a number of neurological disease and cancer models. In addition to inhibiting the MAO-A receptor, it has also been found to bind to the sigma1 receptor, and with high affinity to the I2 imidazoline receptor.

Norharman or beta-carboline (9H-pyrido[3,4-b]indole) is a neuroactive alkaloid first isolated from Peganum harmala L. It is implicated in a number of human diseases including Parkinson's disease, tremor, addiction and cancer. Norharman formed endogenously but external sources have been identified (among others fried meat and fish, meat extracts, alcoholic drinks, coffee brews, tobacco smoke). It inhibits monoamine oxidase and indoleamine 2,3-dioxygenase. In addition norharman binds with high affinity to imidazoline I2B receptors. Plasma norharman levels are elevated in chronic alcoholics and Parkinson's disease patients.

Phenformin is a biguanide hypoglycemic agent with actions and uses similar to those of metformin. It activates AMP-activated protein kinase (AMPK) and inhibits mTORC1 signaling. Phenformin used for the treatment of diabetes. Phenformin was removed from the U.S. market 20 years ago because of a high incidence of lactic acidosis. Risk factors for the development of lactic acidosis include renal deficiency, hepatic disease, cardiac disease, and drug interaction such as cimetidine. Phenformin exerts potential anti-neoplastic action.

Indeloxazine is a neuroleptic, originally developed and marketed in Japan. It is indicated to allay autonomic hyperactivity following cerebral infarction, cerebral haemorrhage or atherosclerosis. It was found to be a weak inhibitor of both type A and type B monoamine oxidases. Indeloxazine-induced facilitation of acetylcholine release in frontal cortex is mediated by endogenous 5-HT and involves at least in part cortical 5-HT4 receptors. As a potential teratogen, Indeloxazine must not be consumed or handled by pregnant or nursing women, or by women who might become pregnant. It was removed from the market reportedly for lack of effectiveness.

Metralindole (Inkazan) is a reversible inhibitor of monoamine oxidase A (RIMA) which was used in Russia as an antidepressant. Inkasan (3-methyl-8-methoxy-3H, 1,2,5,6- tetrahydropyrazine /1.2.3-ab/-beta-carboline hydrochloride) has pharmacological properties characteristic of antidepressants. The clinical antidepressant effect of inkasan is combined with stimulating action. The drug is primarily indicated for patients in whom adynamic (anergic) disturbances are predominant in the clinical picture of depression.

Bifemelane is a psychotropic drug, was found to inhibit monoamine oxidase (MAO). It inhibited type A MAO (MAO-A) competitively and type B (MAO-B) noncompetitively and it was a more potent inhibitor of MAO-A than of MAO-B. Bifemelane is an antidepressant and cerebral activator that is used in Japan for the treatment of cerebral infarction patients with depressive symptoms, and in the treatment of senile dementia as well. It also appears to be useful in the treatment of glaucoma.