Aim: Renal transplant patients are frequently subject to polypharmacy and drug-drug interactions. However, no
previous study has systematically assessed the risk of drug interactions and Adverse Drug Reactions (ADRs) in this
Methods: A total of 138 consecutive adult kidney transplant recipients admitted to our hospital between August 2010 and
February 2012 were prospectively and systematically assessed by our pharmacovigilance team, within 24 hours of
admission, to identify potential drug-drug interactions and probable ADRs.
Results: As a consequence of the high number of medications per patient (7.8±0.2 drugs), a considerable number of drugdrug
interactions were observed in this population, with an average of 5.6±0.4 drug interactions per patient. Moreover, a
significant percentage of admissions (~10%) of kidney transplant patients were related to probable ADRs. Almost all
these patients had at least one drug interaction that could have potentially contributed to the probable ADR. Of note,
clinically significant (i.e. severe) drug interactions were more frequent among patients with ADRs (29% vs. 15%, p<0.01).
Also, patients with ADRs were more likely to have started a medication 30 days before admission (38.5% vs. 10.4%,
p < 0.01). Non-immunosuppressive drugs most commonly involved in severe interactions were omeprazole, magnesium
sulphate, and statins. The most commonly observed interactions were: tacrolimus and omeprazole, mycophenolate and
omeprazole, sirolimus and enalapril, mycophenolate and antivirals, and mycophenolate and magnesium sulphate.
Conclusion: Drug interactions were extremely frequent among kidney transplant recipients, and responsible for
potentially avoidable ADRs. They should be carefully considered when following kidney transplant recipients.