stavudine + didanosine + nelfinavir + hydroxyurea

This is a four-drug combination consisting of **stavudine**, **didanosine**, **nelfinavir**, and **hydroxyurea**, all given as individual agents rather than as a fixed-dose combination. The regimen has been studied as part of intensive antiretroviral therapy for **HIV-1 infection**. - Stavudine is a nucleoside reverse transcriptase inhibitor (NRTI) that inhibits HIV replication by causing DNA chain termination after incorporation into viral DNA. - Didanosine is also a NRTI, working by similar chain termination following incorporation. - Nelfinavir is a protease inhibitor that blocks the HIV-1 protease, preventing maturation of infectious viral particles. - Hydroxyurea is an inhibitor of ribonucleotide reductase that limits deoxynucleotide supply and is believed to potentiate the activity of NRTIs by depleting deoxynucleotide pools, thereby enhancing antiretroviral effect, though it is not considered an antiretroviral agent itself. The combination was evaluated for synergy and intensified viral suppression in HIV-1, but is now rarely used due to toxicity and the development of more effective regimens[1][2][4][5][7].