Phenothiazine, the parent compound of a multitude of present-day drugs, has been employed on an extensive scale for its insecticidal, fungicidal, antibacterial and anthelmintic properties. Phenothiazine was formerly used as an insecticide and as a drug to treat infections with parasitic worms (antihelminthic) in livestock and people. It was introduced as antihelminthic in livestock in 1940 and is considered, with thiabendazole, to be the first modern antihelminthic. Almost a catholicon, its widespread use in animals and man has led to the uncovering of many adverse reactions encompassing effects on blood elements, neuromuscular problems and photosensitization. Its potential side effects have now limited its use. The chemical structure of phenothiazine provides a most valuable molecular template for the development of agents able to interact with a wide variety of biological processes. Synthetic phenothiazines (with aliphatic, methylpiperazine, piperazine-ethanol, piperazine-ethyl, or piperidine side-chain) and/or phenothiazine-derived agents e.g., thioxanthenes, benzepines, imonostilbenes, tricyclic antidepressants, dimetothiazine, and cyproheptadine have been effective in the treatment of a number of medical conditions with widely different etiology. These include various currently clinically used drugs for their significant antihistamic, antipsychotic, anticholinergic (antiparkinson), antipruritic, and/or antiemetic properties.

Theofibrate (Etofylline clofibrate, trade name Duolip) is the clofibric acid ester of theophylline, used for the treatment of hyperlipoproteinaemia with elevated triglycerides and cholesterol. The low dose of Etophylline clofibrate (750mg) has a similar lipid-lowering effect as pure clofibrate (1500mg), probably due to a synergistic hypolipidemic effect with theophylline, which has no lipid-lowering effect per se. Secondly, etophylline clofibrate substantially decreases platelet aggregability and plasma viscosity, properties which may be desirable in the prevention of coronary heart disease (CHD). Finally, etophylline clofibrate is clearly a less potent inducer of peroxisomal proliferation in the rat liver than clofibrate, bezafibrate or fenofibrate. Theofibrate increases lipoprotein lipase activity to promote the conversion of Very low-density lipoprotein (VLDL) to Low-density lipoprotein (LDL), and hence reduce the level of VLDL.

Salinazid (Acozid, Nupasal-213) is an antibacterial agent used primarily as a tuberculostatic. It used to be the treatment of choice for tuberculosis.

Acivicin is a modified amino acid and structural analog of glutamine, that irreversibly inhibits glutamine-dependent amidotransferases involved in nucleotide and amino acid biosynthesis. Acivicin is a potent antitumor agent that induces apoptosis in human lymphoblastoid cells. Phase I dose-escalating studies conducted in cancer patients administered acivicin showed reversible, dose-limiting CNS toxicity, characterized by lethargy, confusion and decreased mental status.

Gestrinone is a synthetic trienic 19-norsteroid developed for the treatment of endometriosis. Gestrinone exerts its activity by activating androgen and progesterone receptors. The drug was approved for use in Latin America, Australia and Europe.

Methylthiouracil is an orally active thyroid enzyme activity inhibitor. Methylthiouracil was introduced in the mid-1940s for the treatment of hyperthyroidism. Methylthiouracil is no longer in clinical use in most countries, although it may be used to a limited degree in some eastern European countries. Methylthiouracil possess anti-inflammatory effects in vitro and in vivo and was found effective in a murine model of sepsis.

Famphur is an insecticide and antihelmenthic. Famphur is approved in cattle as a pour-on (NADA 34-697; 21 CFR 524.900) and as medicated feed (NADA 34-266; 21 CFR 558.254). It is a component of the FDA-approved TRAMISOL X-TRA Combination Paste, used for the treatment of cattle infected with the following parasites: Stomach worms (Haemonchus, Trichostrongylus, Ostertagia), intestinal worms (Trichostrongylus, Cooperia, Nematodirus, Bunostomum, Oesophagostomum), lungworms (Dictyocaulus), cattle grubs (Hypoderma), biting lice (Bovicola), and sucking lice (Linognathus, Solenoptes). Famphur is a cholinesterase-inhibiting drug.

Vincamine is the major alkaloid of Vinca minor. Although vincamine has been used therapeutically for almost three decades, the exact mechanisms of action and its effects are still unknown. Vincamine is a peripheral vasodilator that increases blood flow to the brain. Vincamine is beneficial to the nervous system's cells feeding and protecting processes and is utilized as an adjuvant in case of cerebrovascular insufficiency, age-related psycho-behavioral disorders, post concussion syndrome in head trauma, in case of post-stroke sequels. Vincamine may be used as a dietary nootropic supplement.

Tiratricol (also known as TRIAC or triiodothyroacetic acid) is a thyroid hormone analogue, which has been studied since the 1950s. Tiratricol is used as a dietary supplement for thyroid problems including thyroid cancer. It is also used for increasing metabolic rate for weight loss, and reducing cellulite. In the US, the Food and Drug Administration (FDA) has determined that the product Triax (TRIAC, tiratricol) is not a dietary supplement but an unapproved new drug containing a powerful thyroid hormone, which may cause serious health consequences. The State of Missouri embargoed the product at its distributor (Syntrax) and the Utah-based manufacturer (Pharmatech) has agreed to stop distributing any product containing the ingredient TRIAC. The FDA has issued recalls for other tiratricol-containing products, including Tricana Metabolic Hormone Analogue, Tria-Cutz Thyroid Stimulator Dietary Supplement Capsules, and Sci-Fi-Tri-Cuts Dietary Supplement Capsules. Tiratricol is a prescription drug in France used for therapy of thyroid hormone resistance and therapy of thyroid cancer.

Fenthion (trade names include Baytex™, Baycid™, and Tiguvon™, used on livestock) was first registered domestically in 1965 by the Mobay Corp., a U.S. subsidiary of Bayer AG of West Germany. Fenthion is a contact and stomach insecticide used against many sucking, biting pests, especially fruit flies, stem borers, mosquitoes, and Eurygaster cereal bugs. In mosquitoes, it is toxic to both the adult and immature forms (larvae). Once used extensively in the U.S. for controlling intestinal worms, fenthion no longer has FDA approval due to an excess number of poisoning deaths. Like most other organophosphates, its mode of action is via cholinesterase inhibition. It was used mostly for the control of grubs and lice in beef and nonlactating cattle.