Prevalence of drug-drug interactions of antiretroviral agents in the private health care sector in South Africa

20 April 2010

Objectives. Human immunodefiency virus (HIV) infection can be effectively treated with highly active antiretroviral therapy (HAART), requiring concomitant administration of three to four different agents, often with a high potential for drug-drug interactions (DDIs). This study aimed to determine the prevalence of possible DDIs between antiretrovirals (ARVs) themselves and other drugs. Design. Retrospective drug-utilisation study using data from from a national medicine claims database for the period 1 January to 31 December 2004. Setting. A section of the private healthcare sector in South Africa. Subjects. All ARV prescriptions (N=43482) claimed during 2004. The possible DDIs found were classified according to a clinical significant rating as described by Tatro7 (2005) in his book, “Drug Interactions – Facts and comparisons.” Results. A total of 5305882 medicine items were prescribed, of these, 1.92% (N=101 938) accounted for ARVs. Of the total number of 2595254 prescriptions, 1.68% (N=43 482), were ARVs. A total number of 18035 DDIs (81 different types) were identified, of these, 83.89%, (n=15130) were DDIs between ARVs and other drugs, while 16.11% (n=2905) were DDIs between ARVs themselves. Possible DDIs with a clinical significance level of 1 (major, n=17) and 2 (moderate, n=1436) represented 8.06% (n=1 453) of the total number of identified interactions. Conclusions. Since concomitant use of ARVs and other drugs used to treat HIV complications is increasing, there is a great need of understanding and anticipating these DDIs, overcoming them by dose adjustments and patient education by pharmacists, so that they are not life threatening to HIV/AIDS patients