Drug Interaction Between Oral Cyclosporine Modified and Iron

Objective: To describe a recent case of suspected interaction between oral cyclosporine modified and iron. Case Summary: A 33-year-old man underwent urgent cardiac transplantation for refractory cardiogenic shock caused by acute myocarditis. The patient had persistently low levels of cyclosporine despite a dose increase of the drug after the change of administration route from intravenous to oral. Spacing the administration of cyclosporine modified from oral iron resolved the problem. This drug interaction was reported as “probable” as determined by a Drug Interaction Probability Scale score of 7. Using this scoring system, the patient experienced a probable drug interaction between cyclosporine and iron both administered orally, and we surmise that the mechanism is that iron physicochemically destabilizes the cyclosporine microemulsion when both are administered concurrently. Discussion: This may be because of the interaction between cyclosporine microemulsion and iron because this cation can destabilize the immunosuppressant dosage form. Conclusions: Taking into account that joint administration of oral iron and cyclosporine modified can generate a physicochemical interaction that involves a decrease in the absorption of cyclosporine modified, we believe that it is necessary to recommend spacing administrations of both drugs as well as monitoring levels of cyclosporine in order to ensure optimal levels of immunosuppression.