Moderate
Probable
Description
Concurrent use of acyclovir and cyclosporine can increase nephrotoxicity risk, as both agents are renally cleared and individually nephrotoxic.
Mechanism
Acyclovir causes crystalline nephropathy through renal tubular precipitation at high doses; cyclosporine independently causes afferent arteriolar vasoconstriction; combined renal insult is additive.
Clinical Significance
Case series in transplant recipients show elevated serum creatinine during acyclovir prophylaxis with cyclosporine; both drugs also compete for renal tubular secretion via OAT transporters.
Management
Ensure adequate hydration during IV acyclovir; monitor serum creatinine and cyclosporine trough levels; consider dose reduction of acyclovir in renal impairment.