Testosterone is a steroid sex hormone found in both men and women. In men, testosterone is produced primarily by the Leydig (interstitial) cells of the testes when stimulated by luteinizing hormone (LH). It functions to stimulate spermatogenesis, promote physical and functional maturation of spermatozoa, maintain accessory organs of the male reproductive tract, support development of secondary sexual characteristics, stimulate growth and metabolism throughout the body and influence brain development by stimulating sexual behaviors and sexual drive. In women, testosterone is produced by the ovaries (25%), adrenals (25%) and via peripheral conversion from androstenedione (50%). Testerone in women functions to maintain libido and general wellbeing. Testosterone exerts a negative feedback mechanism on pituitary release of LH and follicle-stimulating hormone (FSH). Testosterone may be further converted to dihydrotestosterone or estradiol depending on the tissue. The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5α-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. Testosterone is used as hormone replacement or substitution of diminished or absent endogenous testosterone. Use in males: For management of congenital or acquired hypogonadism, hypogonadism associated with HIV infection, and male climacteric (andopause). Use in females: For palliative treatment of androgen-responsive, advanced, inoperable, metastatis (skeletal) carcinoma of the breast in women who are 1-5 years postmenopausal; testosterone esters may be used in combination with estrogens in the management of moderate to severe vasomotor symptoms associated with menopause in women who do not respond to adequately to estrogen therapy alone.

Clostebol is a synthetic anabolic-androgenic steroid, a derivative of the natural hormone testosterone. Clostebol is a Schedule III controlled substance used medically in topical ophthalmologic and dermatologic treatments. Due to potential use as a performance-enhancing drug, clostebol is banned by the World Anti-Doping Agency.

Clemizole is a drug in clinical development for the treatment of hepatitis C virus (HCV) infection. Clemizole is a novel inhibitor of TRPC5 channels. Clemizole is an H1 antagonist. Clemizole, an antihistamine drug that was once widely used for treatment of allergic disease, was recently discovered to be a potent inhibitor (IC50, 24 nM) of the interaction between an HCV protein (NS4B) and HCV RNA. Although clemizole was widely used during the 1950s and 1960s, this was before contemporary regulatory requirements were established for new drug development, and there is very minimal information about its pharmacokinetics and metabolism.

Bromperidol (marketed as Bromidol, Bromodol) is a butyrophenone derivative. It is a potent and long-acting neuroleptic, used as an antipsychotic in the treatment of schizophrenia. It was discovered at Janssen Pharmaceutica in 1966. Bromperidol is a bromine analog of Haloperidol hydrochloride (sc-203593) which functions as a D2DR (dopamine D2 receptor) antagonist. Studies suggest that cytochrome CYP3A4 catalyzes the dehydration of Bromperidol and N-dealkylation of Bromperidol. In addition, CYP3A4 can oxidize N-dealkylated Bromperidol back into Bromperidol. Alternately, Bromperidol antagonizes the Neuroendocrine DA receptors which regulate hypothalamic LH-RH release.

Iophendylate (Pantopaque (in USA) or Myodil, formerly manufactures by Glaxo Laboratories (London,UK) was commonly used from the 1940s until the late 1980s for myelography, cisternography, and ventriculography; the use of oil-based contrast agents such as Myodil has been discontinued, and images of intradural oil-based contrast are rarely encountered at present. In 1942 Van Wagenen (a neurosurgical colleague of Warrens, at the University of Rochester) identified Iophendylate as causing chemical meningitis in 30 patients where "space-displacing masses within the spinal canal were suspected". Iophendylate has been shown to be both a radiographic and magnetic resonance (MR) contrast agent in patients with suspected cord abnormalities who underwent MR examination following myelography. The iophendylate appears as a linear band of high signal intensity along the dependent portion of the spinal canal on MR images obtained with a repetition time of 500 msec and an echo time of 30 msec. Recently was published report, where depicted a unique case of posteriorly located subdural trapped Myodil, about three decades after myelography. The clinical picture of that case highlighted that such a complication didn’t carry the risk of arachnoiditis and could remain silent for several decades. Although Iophendylate is not used for evaluation of spinal disease anymore in the modern diagnostic era, its former use and its intrathecal persistence makes its recognition in MR imaging important. That case emphasized the necessity of awareness about these rare features which continue to present even decades after abandonment of oil-based myelography.