Ziagen is a prescription medication that belongs to a class of drugs known as nucleoside reverse transcriptase inhibitors (NRTIs). Its active ingredient is abacavir, which is used in the treatment of HIV (Human Immunodeficiency Virus) infection. Ziagen works by interfering with the reverse transcriptase enzyme, which is crucial for the replication of the HIV virus. By inhibiting this enzyme, abacavir helps to reduce the amount of virus in the body, thereby slowing down the progression of the disease. Ziagen is often used in combination with other antiretroviral medications as part of an antiretroviral therapy (ART) regimen to effectively manage HIV infection. It is important for patients to be tested for a genetic marker called HLA-B*5701 before starting treatment with Ziagen, as those with this marker may have a higher risk of experiencing a hypersensitivity reaction to the medication.