d4T (stavudine, Zerit) is an anti-HIV drug that reduces the amount of virus in the body. Anti-HIV drugs such as d4T slow down or prevent damage to the immune system, and reduce the risk of developing AIDS-related illnesses.

d4T is one of the nucleoside reverse transcriptase inhibitors (NRTIs). These drugs disrupt an HIV enzyme called reverse transcriptase, which is involved in the production of new viruses. For more information about how NRTIs work, see Reverse transcriptase inhibitors.

In May 1996, d4T was approved in Europe as a treatment for HIV in patients who had experienced failure of AZT (zidovudine, Retrovir) treatment or intolerance to AZT. It was approved in the United States in 1994. In August 1997, it received full approval as an initial therapy for the treatment of HIV-infected adults and children over three months of age with progressive or advanced immunodeficiency, when used in combination with other anti-HIV drugs. However, d4T has fallen out of favour as a drug for use in first-line therapy due to the increased risk of body fat side-effects. In June 2003, the British HIV Association recommended against the use of d4T in an initial anti-HIV drug regimen.

d4T is manufactured by Bristol-Myers Squibb. It is also known as stavudine or by its tradename Zerit. Its chemical name is 2’,3’-didehydro-3’-deoxythymidine.

A generic version of d4T known as Stavir is manufactured by the Indian company Cipla. Other generic versions of d4T include Virostav / Avostav (Ranbaxy), Stag (Genixpharma), Stavex (Aurobindo), Stavir (GPO) and Aspen Stavudine.

The World Health Organization recommends that first-line treatment for HIV in resource-limited settings should consist of d4T with 3TC (lamivudine) and nevirapine. This is manufactured as a fixed dose combination by four companies, as Triomune (Cipla), Nevilast (Genixpharma), Stavex LN (Aurobindo Pharma) and ViroLNS / Triviro-LNS (Ranbaxy). Fixed-dose combinations of d4T and 3TC include Lamivir-S (Cipla), Lamistar (Genixpharma), Stavex (Aurobindo) and Virolis / Coviro (Ranbaxy). Each company manufactures tablets containing different doses of d4T according to body weight: 30mg for people below 60kg, and 40mg for people above 60kg.