Incidence and predictors of intravenous acyclovir-induced nephrotoxicity

To assess the incidence, predictive factors, and prognosis of acyclovir-induced nephrotoxicity. We conducted a historical prospective cohort study of patients treated with intravenous acyclovir in North Denmark Region from 2009 to 2016. Information on baseline demographics, co-morbidities, plasma creatinine, and treatment was obtained from the medical records. The primary outcome was an increase of ≥ 40 μmol/L in plasma creatinine level from baseline. We included 276 patients treated with intravenous acyclovir of which 29 (10.5%) met the primary outcome. In 14 cases, the treating physician considered acyclovir the main reason for nephrotoxicity, whereas a potential competing cause of renal impairment was present among the 15 remaining patients. Hypertension was the only predictive factor associated with nephrotoxicity (risk ratio (RR), 2.77; 95% confidence interval (CI), 1.41-5.46), while having no co-morbidities was protective (RR, 0.32; CI, 0.16-0.63). In all cases, the nephrotoxicity was reversible following rehydration and dose reduction or discontinuation of the drug. However, the normalized plasma creatinine upon treatment was significantly higher between cases with acyclovir-induced nephrotoxicity than cases with a potential competing cause (median [interquartile range (IQR)], 93.5 μmol/L [85-108] vs 75 μmol/L [66.5-88]; p = 0.019). Acyclovir-induced, reversible nephrotoxicity was observed in 5.1-10.5% of patients. It is difficult to predict who will develop acyclovir-induced nephrotoxicity; it may occur late in treatment and hypertension was the only independent predictive factor, while the absence of co-morbidities was protective. Ensuring hydration, frequent evaluations of renal function, and corresponding dose adjustment of intravenous acyclovir treatment seem prudent.