Background The launch of a generic form of lamivudine (g3TC), included in several fixed-dose combinations of antiretrovirals (FDCAs), led to considering switching stable patients from lamivudine and emtricitabine-containing FDCAs to separate components including the less expensive g3TC. The Balearic Islands Public Autonomic Health Service ordered, in July 2010, that FDCAs be administered as separate components. In August 2010 they allowed FDCAs to be resumed.

Purpose To assess the cost differences of antiretroviral treatment and adverse drug events management between patients whose FDCAs were discontinued compared to those who maintained their FDCA treatment.

Materials and methods An independent retrospective cost analysis was performed at Son Llatzer Hospital. A total of 75 patients underwent the substitution of their FDCAs to single agents. The authors chose 150 patients matched by gender and type of FDCAs who did not stop taking their FDCAs. For both groups of patients, resource use related to adverse drug events management and drugs administered were collected. The study period assumed for cost calculations was the mean days that patients stayed with the replacement for FDCAs (120 days). An alternative analysis was performed considering the extra appointments (medical visits and analytical procedures) required to monitor those patients whose FDCAs were switched to separate components. Unit costs (€, 2011) were obtained from a Spanish database.

Results Considering the cost of managing antiretroviral treatments and drug-related adverse events, the administration of the components separately increased the total cost by €0.75 per patient per day compared with the FDCA strategy. When the cost of any extra appointments was considered, the total cost increased by €3.6 per patient per day during the study period.

Conclusions Unfortunately stopping FDCAs led to an increase in healthcare expenditure, not the hoped-for decrease.