Some but not all observational studies have found that current exposure to abacavir is associated with increased risk of cardiovascular events such as myocardial infarction, stroke and cardiovascular death. This study aim to investigate possible adverse effect of abacavir on platelet reactivity, coagulation and endothelial activation in HIV-1 infected patients. The study is an open-labeled cross-over trial, where patients receiving antiretroviral therapy containing abacavir switch treatment to a regimen containing tenofovir and vice versa for a period of 90 days.

Inclusion Criteria:

• HIV-1 infected
• Can understand and sign written informed consent
• Received one of the above mentioned antiretroviral regimens continuously ≥ 6 months
• HIV RNA < 400 copies/mL for ≥ 6 months

Exclusion Criteria:

• Receiving anticoagulant therapy, adenosine diphosphate (ADP) receptor inhibitors, aspirin or nonsteroidal antiinflammatory drugs (NSAIDs)
• Previous ischemic heart disease, peripheral atherosclerotic disease or stroke
• Coagulation disorder (e.g. hemophilia, factor V Leiden mutation)
• Platelet count < 150 x 109/L during the past 6 months from inclusion
• Estimated glomerular filtration rate (eGFR) <70 during the past 6 months from inclusion
• Humane leukocyte antigen (HLA)-B*57:01 positive genotype
• Hepatitis B or C positive during the past year from inclusion
• Hypersensitivity to the active substances or to any of the excipients