Sulfisoxazole is a sulfonamide antibacterial antibiotic. The sulfonamides are synthetic bacteriostatic antibiotics with a wide spectrum against most gram-positive and many gram-negative organisms. However, many strains of an individual species may be resistant. Sulfisoxazole acetyl in combination with erythromycin ethylsuccinate is used for treatment of ACUTE OTITIS MEDIA in children that is caused by susceptible strains of Haemophilus influenzae. Sulfisoxazole acetyl is a prodrug of sulfisoxazole. Acetyl group is added to make the drug poorly water soluble, and is hydrolyzed in vivo to the active drug. Sulfisoxazole and its acetylated metabolites are excreted primarily by the kidneys through glomerular filtration. Sulfisoxazole is a competitive inhibitor of the enzyme dihydropteroate synthetase. It inhibits bacterial synthesis of dihydrofolic acid by preventing the condensation of the pteridine with para-aminobenzoic acid (PABA), a substrate of the enzyme dihydropteroate synthetase. The inhibited reaction is necessary in these organisms for the synthesis of folic acid

Metopon was developed as an analgesic opium derivative. This drug has a high affinity to the mu-opioid receptor and produces antinociception through this receptor. Metopon was available in Canada only in tablet form for oral administration; however, because of the drug addiction, the Drug Addiction Committee recommended its limited use.

Sulfaguanidine is used to treat the gastrointestinal infections particularly bacillary dysentery. Sulfaguanidine is a sulfonamide antibiotic that blocks the synthesis of dihydrofolic acid by inhibiting the enzyme dihydropteroate synthase in bacteria. Sulfonamides are active against Gram positive bacteria and Gram negative bacteria.

Ethylmorphine is a derivative of morphine with analgesic and antitussive effect. It acts by activating the opioid receptors and thus has a direct influence on the CNS system. Ethylmorphine was approved in Europe for the treatment of dry cough (Codethyline, Dionine).

The most well known component of willow bark extract is salicin, it is a prodrug, which is gradually transported to the lower part of the intestine, hydrolyzed to saligenin by intestinal bacteria, and converted to salicylic acid after absorption. Salicin possesses an analgesic, anti-inflammatory, and antipyretic properties. Salicin suppressed the activation of MAPKs and NF-κB signaling pathways and thus maybe might be a potential therapeutic agent against inflammatory diseases.

Terpin hydrate is an expectorant commonly used to loosen mucus in patients presenting with acute or chronic bronchitis, and related conditions. Terpin is derived from oil of turpentine, oregano, thyme and eucalyptus. In 1855 Lepin who first investigated terpin reported that it acted upon the mucous membranes and also the nervous system in a manner similar to the oil of turpentine. Terpin hydrate was available in the USA in 1907 in the preparations such as Elixir of Terpin Hydrate alone or in combination with codein or heroin as an antitussives. It was banned by the U.S. Food and Drug Administration (FDA) in the 1990s due to lack of proof of efficacy but is a medicine available in a number of countries worldwide commonly used in combination with codein. At present it is FDA approved for as an OTC use in combination formulations (with acetaminophen and other drugs) used as internal analgesics. Terpin was recently introduced as a natural topical insect repellent.

Cloxyquin has being shown to be a novel activator of the two-pore domain potassium channel TRESK, which is linked to causing migraines and controls the sensitivity of pain nerves in the brain.

Amosulalol is a beta- and alpha-1 adrenoceptor-blocking agent developed for the treatment of hypertension. Amosulalol does not cross blood brain barrier and does not have adverse affect on CNS system.The drug is marketed under the name Lowgan in Japan and Korea.