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Lack of interaction between valaciclovir, the L-valyl ester of aciclovir, and digoxin
J H Soul-Lawton1, B C Weatherley, J Posner
1Glaxo Wellcome Research and Development, Greenford, Middlesex, UK.
Aims:
Changes in both digoxin and aciclovir renal clearance following coadministration with some other renally eliminated drugs have been reported. The potential interaction of valaciclovir, with its antiherpetic metabolite aciclovir, and digoxin was investigated.
Methods:
Twelve healthy volunteers (seven males, five females) participated in an open, randomized, four-period crossover study. Valaciclovir, 1000 mg, was given alone on one occasion, and on another, after the second of two 0.75 mg digoxin doses administered 12 h apart. Blood samples and all urine were collected up to 12 h following the valaciclovir dose for aciclovir radioimmunoassay. On a third occasion, digoxin was given alone and on a fourth, with 1000 mg valaciclovir three times/day for 8 days starting 12 h before the first digoxin dose. Blood samples were taken up to 168 h and all urine collected up to 24 h following the second dose for digoxin radioimmunoassay.
Results:
There were no clinically significant differences in digoxin or aciclovir pharmacokinetic parameters when digoxin or valaciclovir was given alone or in combination.
Conclusions:
No dosage adjustment is required when valaciclovir and digoxin are coadministered.