The Food and Drug Administration (FDA) has approved a number of drugs for treating HIV infection. The first group of drugs used to treat HIV infection, called nucleoside reverse transcriptase (RT) inhibitors, interrupts an early stage of the virus making copies of itself. These drugs may slow the spread of HIV in the body and delay the start of opportunistic infections. This class of drugs, called nucleoside analogs, include:   Product AZT (Azidothymidine) ddC (zalcitabine) ddI (dideoxyinosine) d4T (stavudine) 3TC (lamivudine) Abacavir (ziagen) Tenofovir (viread) Emtriva (emtricitabine)   Manufactured by Glaxo-SmithKline Roche Laboratories, Inc. Bristol-Myers Squibb Bristol-Myers Squibb Glaxo-SmithKline Glaxo-SmithKline Gilead Sciences Inc Gilead Sciences Inc     Health care providers can prescribe non-nucleoside reverse transcriptase inhibitors (NNRTIs), such as: Product Delavridine (Rescriptor) Nevirapine (Viramune) Efravirenz (Sustiva) (in combination with other antiretroviral drugs)   Manufactured by Pfizer Inc Boehringer Ingelheim Pharmaceuticals, Inc. Bristol-Myers Squibb     FDA also has approved a second class of drugs for treating HIV infection. These drugs, called protease inhibitors, interrupt the virus from making copies of itself at a later step in its life cycle. They include: Product Ritonavir (Norvir) Saquinivir (Invirase) Indinavir (Crixivan) Amprenivir (Agenerase) Nelfinavir (Viracept) Lopinavir (Kaletra) Atazanavir (Reyataz) Fosamprenavir (Lexiva)   Manufactured by Abbott Laboratories, Inc. Roche Laboratories, Inc. Merck & Co., Inc. Glaxo-SmithKline Pfizer Inc Abbott Laboratories, Inc. Bristol-Myers Squibb Glaxo-SmithKline       FDA also has introduced a third new class of drugs, known at fusion inhibitors, to treat HIV infection. Fuzeon (enfuvirtide or T-20), the first approved fusion inhibitor, works by interfering with HIV-1's ability to enter into cells by blocking the merging of the virus with the cell membranes. This inhibition blocks HIV's ability to enter and infect the human immune cells. Fuzeon is designed for use in combination with other anti-HIV treatment. It reduces the level of HIV infection in the blood and may be active against HIV that has become resistant to current antiviral treatment schedules. Product Fuzeon   Manufactured by Roche Laboratories, Inc. & Trimeris, Inc.