A 76-year-old female who is being treated with acyclovir (Zovirax) for recurrent genital herpes inf

Fråga: A 76-year-old female who is being treated with acyclovir (Zovirax) for recurrent genital herpes infection shows gradual increase in serum creatinine levels (now 138). Also pathological liver enzyme levels have been recently detected. Acyclovir dose is currently 200 mg x2 peroral (previously 400 mg x2). Could the present kidney and liver changes constitute an adverse drug reaction? The patient is also suffering from recurrent lower urinary tract infections.

Sammanfattning: Acyclovir treatment with 200 mg x2 perorally is an improbable cause of kidney and liver impairment of your patient and further differential diagnosis is warranted.

Svar: Acyclovir induced kidney (1,2) and liver (3) toxicity have been subjects for previous Drugline queries. Briefly, both renal and hepatic impairment have been described, but usually only after intravenous administration of the drug. Effects on renal function are considered to be caused by deposition of crystals of the drug in renal tubules (4). This effect is dose/concentration dependent. Very rarely even acute renal failure (tubular necrosis) can occur. These effects can be avoided by keeping the patient well hydrated, modifying the dose according to renal function and administering the drug slowly. Transient increases in serum creatinine and urea nitrogen have been observed in 14 per cent of patients treated with bolus injections (5).

Treatment increases in serum transaminase levels during acyclovir treatment have been reported (6); however, according to current understanding, acyclovir is not considered hepatotoxic. Mechanisms behind liver transaminase increases are not known.

The Swedish Adverse Drug Reactions Advisory Committee (SADRAC) contains only two cases where acyclovir is considered a possible cause of liver damage. In both cases the drug was given intravenously (7).

Reasons for the gradual decline in renal function and possible liver damage should be further examined. Recurrent urinary tract infections would be a probable explanation for the mild kidney damage of your patient. If other reasons for the liver damage are not found the case should be reported to the Swedish Adverse Drug Reactions Advisory Committee (SADRAC).