Selenium disulfide

Selenium disulfide is sold as an antifungal agent in shampoos (such as Selsun Blue) for the treatment of dandruff and seborrheic dermatitis associated in the scalp with fungi of genus Malassezia. It is also used on the body to treat tinea versicolor (pityriasis versicolor), a type of fungal skin infection caused by a different species of Malassezia. A 2015 systematic review of topical treatments for seborrheic dermatitis of the scalp identified only a single randomized controlled trial evaluating selenium disulfide for the condition. It was a three-arm trial of 246 people with moderate to severe dandruff and compared treatment with 2% ketoconazole shampoo (n=97), 2.5% selenium disulfide shampoo (n=100), and placebo (shampoo base with no antiseborrheic agent) (n=49) for 29days. The study found a 73% reduction in dandruff score with ketoconazole, a 67% reduction with selenium disulfide, and a 45% reduction with placebo. However, the review did suggest use of over-the-counter selenium disulfide shampoos as an inexpensive option for managing mild symptoms of seborrheic dermatitis. In Canada, the 2.5% strength is available over-the-counter. ==Side effects==

Side effects of selenium disulfide shampoo for dandruff appear to be infrequent. The discoloration resolved shortly following discontinuation of selenium disulfide shampoo and its removal could be facilitated by lightly swabbing with isopropyl alcohol. Excessive environmental or occupational exposure to selenium has also been associated with hair loss and other adverse effects. However, hair loss has not been reported with topical selenium disulfide in several large studies. Selenium disulfide should not be applied to damaged skin as there is a risk of systemic absorption and associated toxicity. Systemic symptoms may include tremors, weakness, lethargy, lower abdominal pain, and occasional vomiting. These symptoms usually resolve within 10days following exposure. ==Pharmacology==

Pharmacodynamics Selenium disulfide acts as an antifungal and keratolytic agent to treat seborrheic dermatitis and dandruff. However, application of selenium disulfide to damaged skin can result in systemic absorption and has been associated with cases of toxicity. Selenium disulfide appears to be much less toxic than other selenium salts, which may be attributed to its low aqueous solubility and very poor systemic absorption. ==Chemistry==

Composition Selenium disulfide has a composition that approximates to SeS2 and is sometimes called selenium sulfide. However, as used in proprietary formulations, it is not a pure chemical compound but a mixture of eight-membered-ring compounds where the overall Se:S ratio is 1:2. The specific chemicals contain a variable number of S and Se atoms, SenS8−n. Many selenium sulfides are known, as indicated by 77Se-NMR spectroscopy. ==History==

Selenium sulfide was introduced for medical use in the United States in 1951. causing confusion and contradiction as to exactly what form selenium is in any given topical preparation. ==Society and culture==

Popular culture In the 2001 comedy film Evolution selenium was mentioned as an active ingredient of the anti-dandruff shampoo Head & Shoulders. A group of academics, therefore, tried to use this brand of shampoo to stop an alien invasion after discovering that the alien life form was sensitive to selenium. ==Research==

Selenium disulfide has been suggested to be effective as a treatment for hyperkeratosis based on a small case series of three treated patients. It has also been reported to be effective in the treatment of scalp psoriasis based on clinical observation of over 100treated patients and two case reports of dramatic response. Selenium sulfide is under development for the treatment of meibomianitis (meibomian gland dysfunction) and dry eyes in topical and ophthalmic formulations. As of March 2021, it is in phase 2/3 clinical trials for meibomianitis and phase 2 trials for dry eyes. The developmental code name of selenium sulfide for these uses is AZR-MD-001 and it is being developed by Azura Ophthalmics. == References ==