Identification of potential drug-drug interactions between antiretroviral drugs from prescriptions in the private health-care sector in South Africa.

The aim of this study was to identify potential drug-drug interactions (DDIs) between antiretroviral drugs (ARVs) and to determine whether prescribed daily doses (PDDs) from prescriptions can be used in the evaluation of these interactions. A quantitative, retrospective drug utilization study was performed on 49,995 and 81,096 ARV prescriptions from a South African pharmacy benefit management company, which were prescribed to 7664 and 10,162 HIV patients for 2005 and 2006, respectively. Potential DDIs identified across different age groups were 778 for 2005 and 1155 for 2006; the majority occurred in patients aged 19 to ≤45 years. The potential DDIs identified between ARVs were all interacting at clinical significance level 2 according to guidelines indicated by Tatro. These results demonstrate that potential DDIs were identified between ARVs mostly in three ARV combinations: Kaletra(®) (lopinavir/ritonavir) and efavirenz, lopinavir/ritonavir and nevirapine and combinations of indinavir and ritonavir. There is a need for more education on the prescribing protocols for ARVs in the treatment of HIV-infected patients in the private health-care sector in South Africa.