Metronidazole is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vaginosis. It is effective for dracunculiasis, giardiasis, trichomoniasis, and amebiasis. It is the drug of choice for a first episode of mild-to-moderate Clostridium difficile colitis.

Metrizamide is a nonionic radiopaque contrast agent.

Meticillin is a narrow-spectrum β-lactam antibiotic of the penicillin class. It should not be confused with the antibiotic metacycline. Meticillin was previously used to treat infections caused by susceptible Gram-positive bacteria, in particular, penicillinase-producing organisms such as Staphylococcus aureus that would otherwise be resistant to most penicillins.

Methysergide is a prescription drug formerly used for prophylaxis of cluster headaches/migraine headaches, but is no longer recommended due to retroperitoneal/retropulmonary fibrosis. It is also used in carcinoid syndrome to treat severe diarrhea. It may also be used in the treatment of serotonin syndrome.

Methylscopolamine is an oral medication used along with other medications to treat peptic ulcers by reducing stomach acid secretion. Proton pump inhibitors and antihistamine medications have made this use obsolete. It can also be used for stomach or intestinal spasms, to reduce salivation, and to treat motion sickness. Methscopolamine is also commonly used as a drying agent, to dry up post-nasal drip, in cold, irritable bowel syndrome and allergy medications.

Methotrimeprazine is a phenothiazine neuroleptic drug. It is a low-potency antipsychotic (approximately half as potent as chlorpromazine) with strong analgesic, hypnotic and antiemetic properties that is primarily used in palliative care. Serious side effects include tardive dyskinesia, akathisia, abnormalities in the electrical cycle of the heart, low blood pressure and the potentially fatal neuroleptic malignant syndrome. As is typical of phenothiazine antipsychotics, levomepromazine is a "dirty drug", that is, it exerts its effects by blocking a variety of receptors, including adrenergic receptors, dopamine receptors, histamine receptors, muscarinic acetylcholine receptors and serotonin receptors. (Source: https://en.wikipedia.org/wiki/Levomepromazine).

Methylergonovine Maleate is the maleate salt of methylergonovine, a semi-synthetic ergot alkaloid with vasoconstrictive and uterotonic effects. Methylergonovine stimulates serotoninergic and dopaminergic receptors as well as inhibits the release of endothelial-derived relaxation factor. This results in arterial vasoconstriction and increased uterine smooth muscle contractions.

Methyclothiazide is a thiazide diuretic with properties similar to those of Hydrochlorothiazide.

Mesuximide is a succinimide anticonvulsant medication. It is sold as a racemate by Pfizer under the tradenames Petinutin and Celontin. The therapeutic efficacy of methosuximide is largely due to its pharmacologically active metabolite, N-desmethylmethosuximide, which has a longer half-life and attains much higher plasma levels than its parent.

Methoxamine Hydrochloride is an alpha-1 adrenergic agonist that causes prolonged peripheral vasoconstriction.

Methdilazine Hydrochloride is a first-generation antihistamine with anticholinergic properties of the phenothiazine class.

Methazolamide is a carbonic anhydrase inhibitor that is used as a diuretic and in the treatment of glaucoma. Methazolamide inhibits tumor-associated carbonic anhydrase IX (CAIX), which may result in increased cell death in hypoxic tumors. As a hypoxia-inducible transmembrane glycoprotein, CAIX catalyzes the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions, helping to maintain acidification of the tumor microenvironment and enhance resistance to cytotoxic therapy in some hypoxic tumors.

Methantheline Bromide is a synthetic antispasmodic. It is used to relieve cramps or spasms of the stomach, intestines, and bladder. Methantheline is used to treat intestine or stomach ulcers (peptic ulcer disease), intestine problems, pancreatitis, gastritis, biliary dyskinesia, pylorosplasm, or urinary problems.

Metaraminol bitartrate is a sympathomimetic agent that acts predominantly at alpha-1 adrenergic receptors. It has been used primarily as a vasoconstrictor in the treatment of hypotension.

Mesoridazine besylate is a phenothiazine dopamine receptor anatagonist. Mesoridazine besylate is described to demonstrate inhibition for D2DR and D4DR. It has a high affinity for dopamine D4 receptor. Mesoridazine besylate is an antipsychotic agent.

Mepyramine maleate, also known as Pyrilamine maleate, is a histamine H1 antagonist. It has mild hypnotic properties and some local anesthetic action and is used for allergies (including skin eruptions) both parenterally and locally. It is a common ingredient of cold remedies.

Mepivacaine Hydrochloride is a local anesthetic. It reversibly blocks inward current of transient Na+, as well as the steady-state K+ outward current. Mepivacaine Hydrochloride blocks tandem pore (TASK) and Kv1.5, potassium channels in model systems.

Mepenzolate Bromide is a muscarinic antagonist used to treat gastrointestinal disorders. It decreases the severity of elastase-induced airspace enlargement and respiratory dysfunction.

Memantine Hydrochloride is the hydrochloride salt of memantine, a low-affinity, voltage-dependent, noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Memantine binds to and inhibits cation channels of glutamanergic NMDA receptors located in the central nervous system, preventing the prolonged influx of calcium ions and the associated neuronal excitotoxicity, and thereby potentially enhancing cognitive function. Memantine is also a 5-hydroxytryptamine type 3 (5HT3) receptor and nicotinic receptor antagonist.

Mefenamic Acid is a non-steroidal anti-inflammatory agent with analgesic, anti-inflammatory, and antipyretic properties. It is an inhibitor of cyclooxygenase and has demonstrated antiproliferative activity against colorectal cancer cells.

Meclofenamic acid is a drug used for joint, muscular pain, arthritis and dysmenorrhea. Meclofenamic acid is a non-steroidal anti-inflammatory agent with antipyretic and antigranulation activities. It also inhibits prostaglandin biosynthesis. It is a member of the anthranilic acid derivatives class of NSAID drugs and was approved by the FDA in 1980. Like other members of the class, it is a COX inhibitor and prevents formation of prostaglandins.

Meclizine dihydrochloride is a histamine H1 antagonist used in the treatment of motion sickness, vertigo, and nausea during pregnancy and radiation sickness. Meclizine hydrochloride increases human pregnane X receptor (hPXR) target gene expression in human hepatocyte primary cultures.

Maprotiline Hydrochloride is the hydrochloride salt form of maprotiline, a tetracyclic antidepressant closely related to the tricyclic antidepressants with adrenergic activity and sedative properties. Maprotiline hydrochloride exerts its effect by blocking the re-uptake of norepinephrine, thereby increasing the synaptic concentration of norepinephrine in the central nervous system and subsequently prolonging the action of norepinephrine on central receptors.

Malathion is an organophosphorous compound that inhibits cholinesterase enzyme activity. Malathion contains an interesting phosphinothioyl-thio ester as its active moiety where modification of acetylcholinesterase occurs. The action of Malathion on acetylcholinesterase has been correlated to prolonged modulation of the functioning of the cutaneous vasculature. Malathion is an organophosphate insecticide of relatively low human toxicity.

Lumefantrine, also known as HSDB 7210, is an antimalarial agent used to treat acute uncomplicated malaria. It is administered in combination with artemether for improved efficacy. This combination therapy exerts its effects against the erythrocytic stages of Plasmodium spp. and may be used to treat infections caused by P. falciparum and unidentified Plasmodium species, including infections acquired in chloroquine-resistant areas.

Lofexidine Hydrochloride is an alpha2-adrenergic receptor agonist that is structurally related to Clonidine and used in the treatment of opioid withdrawal symptoms as well as an anihypertensive. It can be used as a short acting anti-hypertensive.

Lisuride maleate is an ergot derivative that acts as an agonist at dopamine D2 receptors, a dopamine agonist. It may also act as an antagonist at dopamine D1 receptors, and as an agonist at some serotonin receptors. It displays high affinity for D2, D3 and D4 receptors along with 5-HT1A. Lisuride maleate is also known as an anti-Parkinson's agent.

Lindane is an organochlorine chemical variant of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and scabies. Lindane is a neurotoxin that interferes with GABA neurotransmitter function by interacting with the GABAA receptor-chloride channel complex at the picrotoxin binding site. In humans, lindane affects the nervous system, liver and kidneys, and may well be a carcinogen. It is unclear whether lindane is an endocrine disruptor.

Levobunolol is a non-selective beta blocker. It is used topically to manage glaucoma.

Labetalol is a mixed alpha/beta adrenergic antagonist that is used to treat high blood pressure. It can be given intravenously in severe hypertensive situations, or by mouth for long term hypertension management. Studies suggest that the pharmacokinetics of labetalol are significantly affected by the common CYP2C19 polymorphisms.