We comply with the HONcode standard for trustworthy health information - We report a case of crystalluria in a patient treated empirically with intravenous acyclovir for possible viral meningitis. Renal function has to be checked often in patients given acyclovir for appropriate dose titration. Despite a neurological improvement, she developed an acute renal insufficiency with the serum creatinine increasing from 63 to 385 micromol/L within 12 days. Finally, 4 metabolites (guanine, 4-guanidinobutyric acid, creatinine, and urea) were identified, which can be used for further research on the mechanism of ACV-induced nephrotoxicity.Introduction Time-of-addition assays, performed with compound A, suggested that this molecule at an early time point of the HSV replication cycle. After the second infusion, the patient began to suffer from visual hallucinations, confusion and acute renal failure. Twenty-four rats were randomly divided into four groups: a 0.9% NaCl solution group, and 100, 300, and 600 mg/kg ACV-treated groups; the ACV or vehicle solution was administered with a single intravenous injection. Compound A inhibited HSV-1 replication in Vero cells with an EC(50) of 1.3 and 1.4 microM for an acyclovir (ACV)-sensitive strain and an ACV-resistant strain of this virus, respectively. Acyclovir treatment was suspended and renal function replacement therapy was initiated. Intratubular crystal precipitation of the drug may represent a major pathogenetic mechanism. The results support clinical pathology data in humans and suggest that HK-2 cells are a suitable model to use in in vitro toxicity studies to determine drug-induced nephrotoxicity in humans.The antiviral molecule acyclovir can be responsible of severe renal dysfunction. We hypothesized that acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity. Analysis of the cerebrospinal fluid was normal, but herpetic meningo-encephalitis was suspected and intravenous treatment was initiated with acyclovir. The significance of 'decoy cells' in the urine as a marker of polyomavirus BK reactivation was also discussed, both in renal transplantation and other conditions such as solitary pancreas transplantation, chronic lymphatic leukaemia, and HIV infection. The porcine renal proximal tubular cell line LLC-PK1 is routinely used to study the nephrotoxic effects of drugs in humans. Clinical evidence of nephrotoxicity in the absence of crystalluria suggests that acyclovir induces direct insult to renal tubular cells. Finally, they reported on the utility and limits of flow cytometry for the automated analysis of urine sediments. Patients recover prompt from the adverse effects at drug withdrawal.The antiviral molecule acyclovir can be responsible of severe renal dysfunction. The authors reviewed the main contributions dealing with urine sediment examination, published in international journals in the period from January 2002 to April 2003. Intravenous acyclovir was delivered at the dose of 45 mg/kg per day. Consecutive series of 60 patients on oral acyclovir and 20 patients on intravenous acyclovir were studied in order to define the frequency of acyclovir crystalluria. Compound B also inhibited the ACV-sensitive and -resistant HSV-1 strains, and HSV-2 at EC(50) values of 1.7, 1.9 and 1.6 microM, respectively. Withdrawal of acyclovir treatment in combination with oral and parenteral hydration resulted in a complete recovery of the renal function. OBSERVATION: Urine was collected at different time periods (12 h before administration, and 0–6 h, 7–12 h, and 13–24 h after administration). HK-2 cells metabolized IFO to its nephrotoxic metabolite, chloroacetaldehyde (CAA). 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