Drug-Drug Interactions as a Challenge in the Treatment of HIV/AIDS

Human immunodeficiency virus (HIV) is a major challenge in the medical fraternity worldwide. According to the UNAIDS report on the global AIDS epidemic, in 2004 it had affected more than 42 million people, and of these 25 million resided in the sub-Sahara Africa (UNAIDS, 2004 & Bhigjee, 2005). This virus has no cure; the lives of the infected patients can only be prolonged using lifelong highly active antiretroviral (ARV) therapy (HAART). HAART has been proven to suppress HIV-1 viral replication continuously thus reducing mortality and morbidity in treated patients. It has further been proven that HAART is only highly effective if prescribed in combination of more than 2 drugs. However these drug combinations can be presented with potential drug-drug interactions (DDIs) an important cause of adverse drug reactions (ADRs) (Highleyman, 2007). DDIs are well-recognised causes of adverse drug effects (ADEs) (Bates et al., 1995). According to Juurlink et al. (2003), DDIs do cause particularly important type of adverse drug event because they are often predictable based on previous reports, clinical studies, and an understanding of pharmacological principles. According to Johnson et al. (1999), DDIs are classified as an important category of ADEs. Drug interactions result in undesirable modification of the action of one or more concurrently administered agents. The interaction may cause treatment failure, an increased pharmacologic effect, or a toxic effect, which may be fatal. Because DDIs usually have a specific time course (i.e., onset and duration), they are more predictable (and preventable) then ADRs (adverse drug reactions). Bates et al. (1999) state that Preventable DDIs account for about one third of ADEs but incur about one half of the total ADE costs. In HIV-infected patients, the introduction of HAART has led to reduced morbidity and mortality in treated patients (Egger et al., 2002). However, in a substantial proportion of patients, the effectiveness of HAART has not been sufficient due to occurrence of virological failure and immunological decay (Bartlett et al., 2001). All this has been due to failure to determine drug interactions and prevention of toxic effects. (Boffito et al., 2005). The possible causes of DDIs include drug combinations, lack of communication between the prescribers and medical history, increase in the number of newly marketed drugs and polypharmacy. Specific patients who are risk for DDIs include the elderly, people living with HIV/AIDS. Patients with HIV are more at risk for the virus because they are treated