In this case report, we examine the impact of a simplified two-drug highly active antiretroviral therapy (HAART) regimen of raltegravir and lamivudine in a patient co-infected with human immunodeficiency virus (HIV) and hepatitis C, D and B viruses (HCV/HDV/HBV) under immunosuppressive therapy after liver transplantation. Pharmacokinetic interactions between integrase inhibitors and immunosuppressant drugs are described. Raltegravir, the first integrase inhibitor, associated with lamivudine, was introduced because its metabolism does not interfere with immunosuppressant therapy. During post-orthotopic liver transplantation follow-up, the patient’s transaminases level increased and his antiretroviral therapy (HAART) of tenofovir/emtricitabine and fosamprenavir was changed, due to suspected drug toxicity. After seven months of follow-up, the patient showed good tolerance, good viro-immunological control with undetectable HIV viraemia and stable concentrations of immunosuppressive drugs. This case indicates that the combination of raltegravir and lamivudine is an optimal and effective strategy because it resulted in an important reduction of hepatic transaminases in a patient with very critical clinical conditions.