Emtricitabine and tenofovir are antiretroviral drugs used to treat HIV/AIDS, in combination with other antiretrovirals. They are often combined in a single preparation and may also be combined with a third drug, such as efavirenz. The different combinations are known by different trade names according to country and manufacturer. In most countries antiretrovirals are available by prescription only as they require careful selection and monitoring of treatment.
AIDS is the acronym for Acquired Immune Deficiency Syndrome (AIDS), which is a highly transmissible disease caused by the Human Immunodeficiency Virus (HIV). Transmitted by body fluids, it is incurable, so prevention is vital. Transmission occurs most often through sexual contact but it may be transmitted by other methods including from mother to child during pregnancy and through the sharing of needles, a common practice amongst drug addicts.
HIV works by destroying the body’s immune system, leaving it vulnerable to infections. The virus multiplies in the body rapidly, causing a decline in immunity. HIV treatment is given to slow the viral replication and the time of initiation of treatment is usually determined by monitoring the CD4 count, which is an indication of immune status. HIV treatment aims to lower the HIV viral load to lower than detectable levels.
Emtricitabine and tenofovir both act by imitating the substrate for reverse transcriptase, which is an enzyme needed for the HIV to convert RNA to DNA. By imitating it, they block its action and slow down viral replication. Emtricitabine and tenofovir, while both having the same effect, act at slightly different points. Tenofovir is a nucleotide reverse transcriptase inhibitor and emtricitabine is a nucleoside reverse transcriptase inhibitor.
When treating HIV infection, at least three drugs are used in combination to prevent the development of a resistant virus. Emtricitabine and tenofovir may be used together with an antiretroviral from another class, such as a non-nucleoside reverse transcriptase inhibitor like nevirapine or efavirenz or a protease inhibitor such as lopinavir boosted with ritonavir. The choice of combination will be decided by the prescribing doctor, taking into consideration the patient's clinical history.
It is vital that all antiretroviral medications, including emtricitabine and tenofovir and whichever third drug is prescribed are taken exactly as prescribed. Due to the constantly replicating nature of HIV, resistance can develop quickly and adherence is vital to keep the viral load down. The normal emtricitabine and tenofovir dose is 300 mg tenofovir and emtricitabine 200 mg daily. The antiretrovirals may interact with other medications and may cause adverse effects in some patients. These should be discussed with the prescribing doctor before commencing treatment.