Antimicrobial and immunosuppressive drug interactions in solid organ transplant recipients

Infections are frequent and can be severe in recipients of solid organ transplantation. Prevention and treatment are priority objectives of multidisciplinary transplant teams. Interactions between antimicrobials (indicated for prevention and therapy) and immunosuppressants (for preventing rejection) make treatment more complex than in the general population. Co-administration of immunosuppressants and antibiotics can cause harmful interactions, modifying the pharmacokinetic and pharmacodynamic characteristics of both groups of drugs. The loss of the transplanted organ due to reduced levels of immunosuppressants is a unique consequence of the often lethal interactions in this group of patients. By contrast, elevated levels of these drugs cause toxicity, and reduced concentrations of antimicrobial treatment fail to contain the infection. Azoles, rifabutin, protease inhibitors, non-nucleoside reverse transcriptase inhibitors and antimicrobial macrolides all interact with immunosuppressants. In this article, we review interactions between antibiotics and immunosuppressants in order to adopt the most appropriate clinical approach (dosage adjustments, close monitoring of plasma levels and organ function) and determine whether they can be used together with any measure of safety.