Olsalazine is an anti-inflammatory drug used in the treatment of inflammatory bowel disease such as ulcerative colitis. Like balsalazide, olsalazine is believed to deliver mesalazine, or 5-aminosalicylic acid (5-ASA), past the small intestine, directly to the large intestine, which is the active site of disease in ulcerative colitis.

Olopatadine is an antihistamine, as well as anticholinergic and mast cell stabilizer. It is used to treat itching associated with allergic conjunctivitis (eye allergies). There is also a potential for Olopatadine as a treatment modality for steroid rebound (red skin syndrome).

Ofloxacin is a synthetic antibiotic of the fluoroquinolone drug class considered to be a second-generation fluoroquinolone.

Nortriptyline is a second-generation tricyclic antidepressant (TCA). It is used in the treatment of major depression and childhood nocturnal enuresis (bedwetting). Its off-label uses include treatment of chronic fatigue syndrome, chronic pain and migraine, and labile affect in some neurological disorders.

Norgestimate is an acetylated progestinused in combination with ethinyl estradiol as an oral contraceptive. It acts as a prodrug to norelgestromin (17-deacetylnorgestimate or levonorgestrel 3-oxime), the primary active metabolite, and levonorgestrel (deacetylation of norgestimate occurs in the intestines and the liver). Unlike levonorgestrel, norgestimate shows high selectivity for the progesterone receptor and low androgenic action due to a large drug-induced elevation in the level of sex hormone-binding globulin (SHBG) (which preferentially binds androgens and thus inhibits their action). In accordance, clinical trials have observed minimal androgenic side effects. Norgestimate and its metabolites themselves, unlike many other progestins, do not bind to SHBG.

Norfloxacin is a synthetic chemotherapeutic antibacterial agent occasionally used to treat common as well as complicated urinary tract infections. It is a first generation synthetic fluoroquinolone (quinolone) and is approved for the treatment of urinary tract infections, prostatitis, and sexually transmitted diseases, although it is no longer used for the latter due to bacterial resistance.

Norepinephrine is an organic chemical in the catecholamine family that functions in the human brain and body as a hormone and neurotransmitter. Norepinephrine directly stimulates adrenergic receptors. Stimulation of alpha-adrenergic receptors causes vasoconstriction of the radial smooth muscle of the iris, arteries, arterioles, veins, urinary bladder, and the sphincter of the gastrointestinal tract. Stimulation of beta-1 adrenergic receptors causes an increase in myocardial contractility, heart rate, automaticity, and atrioventricular (AV) conduction while stimulation of beta-2 adrenergic receptors causes bronchiolar and vascular smooth muscle dilatation.

Norelgestromin is a steroidal progestin used in contraceptive patches, where it is combined with the estrogen ethinyl estradiol. It is one of the active metabolites of norgestimate.

Nizatidine is a histamine H2 receptor antagonist that inhibits stomach acid production. It is commonly used in the treatment of peptic ulcer disease and gastroesophageal reflux disease.

Nitroxoline is an antibiotic that has been in use in Europe for about fifty years, and has proven to be very effective at combating biofilm infections. Nitroxoline was shown to cause a decrease in the biofilm density of P. aeruginosa infections, which would allow access to the infection by the immune system in vivo. It was shown that nitroxoline functions by chelating Fe2+ and Zn2+ ions from the biofilm matrix; when Fe2+ and Zn2+ were reintroduced into the system, biofilm formation was reconstituted. The activity of biofilm degradation is comparable to EDTA, but has a history of human use in clinical settings and therefore has a precedent with which to allow its use against “slimy” biofilm infections.

Nitrofurazone is a topical anti-infective agent that is effective against gram-negative and gram-positive bacteria. It is used for superficial wounds and injuries and skin infections. Nitrofurazone has also been administered orally in the treatment of trypanosomiasis.

Nitrofurantoin is an antibiotic used to treat bladder infections. Although sulfonamides and antibiotics are usually the agents of choice for urinary tract infections, nitrofurantoin is widely used for prophylaxis and long-term suppression. It is not effective for kidney infections.

Niflumic acid is a drug used for joint and muscular pain. It is categorized as an inhibitor of cyclooxygenase-2. In experimental biology, it has been employed to inhibit chloride channels. Niflumic acid has also been reported to act on GABA-A and NMDA channels and to block T-type calcium channels.

Nicergoline is an ergot derivative used to treat senile dementia and other disorders with vascular origins. It has been found to increase mental agility and enhance clarity and perception. It decreases vascular resistance and increases arterial blood flow in the brain, improving the utilization of oxygen and glucose by brain cells. It has similar vasoactive properties in other areas of the body, particularly the lungs. Nicergoline is used for vascular disorders such as cerebral thrombosis and atherosclerosis, arterial blockages in the limbs, Raynaud's disease, vascular migraines, and retinopathy.

Naratriptan is a triptan drug marketed by GlaxoSmithKline and is used for the treatment of migraine headaches. Naratriptan is available in 2.5 mg tablets. It is a selective 5-HT1 receptor subtype agonist.

Naftifine is an allylamine antifungal drug for the topical treatment of tinea pedis, tinea cruris, and tinea corporis (fungal infections). Its precise mechanism of action is unknown, but may involve selectively blocking sterol biosynthesis via inhibition of the squalene 2,3-epoxidase enzyme. The half-life is approximately 2–3 days. The metabolites are excreted in the urine and feces.

Nadolol is a non-selective beta blocker used in the treatment of high blood pressure and chest pain. Additionally, it is often prescribed in the treatment of atrial fibrillation, migraine headaches, and complications of cirrhosis.

Moricizine is an antiarrhythmia agent used primarily for ventricular rhythm disturbances.

Misoprostol is a medication used to start labor, cause an abortion, prevent and treat stomach ulcers, and treat postpartum bleeding due to poor contraction of the uterus. For abortions it is often used with mifepristone or methotrexate. By itself effectiveness for this purpose is between 66% and 90%.

Miconazole is an imidazole antifungal agent commonly applied topically to the skin or to mucous membranes to cure fungal infections. It works by inhibiting the synthesis of ergosterol, a critical component of fungal cell membranes. It can also be used against certain species of Leishmania protozoa which are a type of unicellular parasites that also contain ergosterol in their cell membranes. In addition to its antifungal and antiparasitic actions, it also has some antibacterial properties.

Mezlocillin is a broad-spectrum penicillin antibiotic. It is active against both Gram-negative and some Gram-positive bacteria. Unlike most other extended spectrum penicillins, it is excreted by the liver, therefore it is useful for biliary tract infections, such as ascending cholangitis.

Metyrapone is a drug used in the diagnosis of adrenal insufficiency and occasionally in the treatment of Cushing's syndrome (hypercortisolism). It blocks cortisol synthesis by reversibly inhibiting steroid 11β-hydroxylase. This stimulates ACTH secretion, which in turn increases plasma 11-deoxycortisol levels.

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.