Objective and methods: The aim of our study was to analyse retrospectively the nature and frequency of antiretroviral prescriptions for 990 HIV-infected patients followed at our outpatient centre in Bologna, Italy, from January 2003 to March 2004. The main focus of the study was to identify the most commonly prescribed combinations and their related expenses, in order to identify the most competitive treatment regimens with regard to costs. Prescriptions were given directly to patients at monthly intervals, and drug treatment adherence data was stored in an electronic database. Antiretroviral regimens administered for the longest period to each patient during the 15 months of the study were selected for the study. All patients treated for <9 consecutive months and/or with treatment adherence levels <90% were excluded. Physicians assessed antiretroviral therapy at least quarterly according to efficacy and safety criteria, but not in terms of pharmacoeconomic considerations. Direct pharmacy expenses were obtained for the 24 most commonly used therapeutic regimens, covering 80.1% of patients.
Results: The zidovudine-lamivudine-efavirenz combination proved to be the most prescribed combination (7.3%), followed by zidovudine-lamivudine- nevirapine (7.1%), lamivudine-stavudine (6.2%), zidovudine-lamivudine- lopinavir-ritonavir (5.2%), didanosine-stavudine-lopinavir-ritonavir (4.8%), and lamivudine-stavudine-nevirapine (4.7%). Anti-HIV combinations varied from a minimum yearly cost of euro3895.6 for lamivudine-stavudine to euro9422.8 for the zidovudine-lamivudine-lopinavir-ritonavir combination (+241.9%) [year of costing 2003]. There was a significant difference between the two first-line regimens for antiretroviral-naive subjects, with lopinavir-ritonavir-based combinations costing more than euro9000 per patient/year compared with efavirenz-containing combinations, which were 28% less expensive. Mean daily costs varied substantially, from a minimum of euro10.7 per day for lamivudine-stavudine to a maximum of euro25.8 per day (+241.1%) for zidovudine-lamivudine-lopinavir-ritonavir. Regimens based on non-nucleoside reverse transcriptase inhibitors (NNRTIs) were less costly than most of those including protease inhibitors (PIs). The increased expense of each combination was compared with the cheapest therapeutic selection (lamivudine-stavudine), and costs of all triple combinations were also compared. Regimens based on NNRTIs accounted for 29.3% of our cohort (nevirapine-containing therapies 15.1%, and efavirenz-based ones 14.2%), while PIs were used in the majority of cases (37.3%), with lopinavir-ritonavir as the leading combination (13.6% of patients), followed by nelfinavir (9.9%) and indinavir (9.2%). When drug-related costs were examined, dual nucleoside analogues showed the lowest expense (euro10.7-euro11.6 per day), while triple nucleoside/nucleotide analogue combinations cost nearly twice as much (euro18.5-euro20.4 per day). Among the NNRTIs, there were comparable costs for nevirapine-based combinations (euro18.3-euro18.7 per day), while efavirenz-including regimens were 10% more costly (euro19.2-euro20.l per day). A very broad range of combinations and related costs were found with PIs, but apart from indinavir and saquinavir combinations (euro15.7-euro21.7 per day), all other regimens had a higher daily cost (from euro22.0 per day for ritonavir-based regimens to euro23.4-euro24.3 per day for nelfinavir combinations, and up to euro24.9-euro25.8 per day with lopinavir-ritonavir). When considering nelfinavir- and lopinavir-containing combinations, the difference compared with NNRTI-based regimens varied from 41% when nevirapine- and lopinavir-ritonavir were compared, to 11.6% when efavirenz and nelfinavir were compared.
Conclusions: Investigations that link prescribing patterns and related costs in the setting of HIV disease therapy are needed to improve patient management and help with the planning of healthcare resource allocation.