Management of cytomegalovirus infection in solid-organ transplant recipients

Ganciclovir Pharmacokinetics and Individualized Dosing Based on Covariate in Lung Transplant Recipients

The aim of this prospective study was to evaluate the pharmacokinetics of ganciclovir in lung transplant recipients, to explore its covariates, and to propose an individualized dosing regimen. Ganciclovir was administered according to the protocol in a standardized intravenous dose of 5 mg/kg twice daily. Serum ganciclovir concentrations were monitored as a trough and at 3 and 5 h after dosing. Individual ganciclovir pharmacokinetic parameters were calculated in a two-compartmental pharmacokinetic model, while regression models were used to explore the covariates. Optimal loading and maintenance doses were calculated for each patient. In lung transplant recipients (n = 40), the median (IQR) ganciclovir total volume of distribution and clearance values were 0.65 (0.52–0.73) L/kg and 0.088 (0.059–0.118) L/h/kg, respectively. We observed medium-to-high inter-individual but negligible intra-individual variability in ganciclovir pharmacokinetics. The volume of distribution of ganciclovir was best predicted by height, while clearance was predicted by glomerular filtration rate. Bodyweight-normalized clearance was significantly higher in patients with cystic fibrosis, while distribution half-life was reduced in this subgroup. On the basis of the observed relationships, practical nomograms for individualized ganciclovir dosing were proposed. The dosing of ganciclovir in patients with cystic fibrosis requires special caution, as their daily maintenance dose should be increased by approximately 50%.

Cytomegalovirus Disease Amongst Renal Transplant Recipients in Australia and New Zealand

Cytomegalovirus (CMV) is a significant pathogen causing disease in renal transplant patients. The highest incidence of CMV disease occurs during the first 3 months post-transplant and is most problematic in CMV-naïve transplant recipients. In this study, we conducted a retrospective review of two databases, the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) and the National Hospital Morbidity Database, from the Australian Institute of Health and Welfare (AIHW), to examine CMV in renal transplant recipients. The first source looked at CMV serostatus at the time of transplantation and the second recorded hospital admissions for recipients with invasive CMV disease.

From the ANZDATA registry, we obtained information from 13,530 renal transplants recipients from 1980 to 2004. Of these recipients, 7808 had a known CMV serostatus, of which 65.7% (5134/7808) had a positive sero antibody status and 34.2% (2674/7808) had a negative sero antibody status. In univariate analysis, factors significantly associated with renal rejection were being male, recipient age <50 years, being diabetic, being diagnosed with cancer at some point and having a positive EBV status. Positive CMV serostatus was not a contributing factor. Between 1993 and 2001 there were 1445 renal transplant recipients hospitalized in Australia with a diagnosis of CMV disease, of which 38% (554/1445) had CMV disease as a principal diagnoses. The average annual rate of admissions with any diagnosis was 3871 episodes per 100,000 people living with a functioning graft.

Preventative strategies for CMV in renal transplant recipients should be a priority. New vaccines for CMV may soon be available and renal transplant recipients would be a suitable target group for vaccination.

A comparative randomised study of valacyclovir vs. oral ganciclovir for cytomegalovirus prophylaxis in renal transplant recipients

An open, prospective, randomised study was conducted to compare the safety and efficacy of valacyclovir vs. oral ganciclovir for cytomegalovirus (CMV) prophylaxis in renal transplant recipients. Eighty-three renal transplant recipients were assigned randomly to receive valacyclovir (n=43) or oral ganciclovir (n=40) for the first 3 months after transplantation. Both groups were similar in terms of demographics, primary renal disease, graft source, HLA matching, immunosuppressive therapy and donor-recipient CMV antibody status. CMV infection was diagnosed by detection of virus DNA in plasma with the Amplicor CMV Test. CMV disease was observed in only one patient belonging to the ganciclovir group, who developed enterocolitis 6 months post-transplantation. No difference was observed between the two treatment groups with respect to detection of CMV DNA, virus infections other than CMV, acute rejection episodes, and serum creatinine levels at 3 and 6 months following transplantation. An increased number of bacterial infections was noted in the ganciclovir group (p 0.003). No adverse reactions with either treatment were reported. The estimated cost of valacyclovir treatment was 20% higher than that of ganciclovir treatment. Overall, both valacyclovir and oral ganciclovir were found to be effective and safe for CMV prophylaxis in renal transplant recipients. Decisions regarding prophylactic regimens should include additional criteria, such as cost or possible development of resistance.

Ganciclovir in solid organ transplant recipients: is there a role for clinical pharmacokinetic monitoring?

The authors use a previously published decision-making algorithm to address the role of clinical pharmacokinetic monitoring of ganciclovir, the drug of choice for prophylaxis and treatment of cytomegalovirus (CMV) in solid organ transplant recipients. Ganciclovir pharmacokinetics have been studied in solid organ transplant recipients with a wide range of peak and trough concentrations reported. Numerous assays are available to measure plasma concentrations of ganciclovir, but no clear correlation has been established between peak or trough concentrations and either efficacy or toxicity of the drug. For patients receiving treatment, the pharmacological response of ganciclovir is assessed initially by clinical response. Monitoring prophylactic therapy in asymptomatic patients poses a greater challenge. Although monitoring of antigenemia or polymerase chain reaction (PCR) deoxyribonucleic acid (DNA) is not yet part of routine clinical practice, studies have shown a role for these techniques in monitoring response to antiviral therapy. Studies of subpopulations of renal failure patients show a prolonged ganciclovir half-life that requires dosage adjustments. However, ganciclovir clearance is closely correlated with creatinine clearance, which is an appropriate approach to adjusting dosages. Studies in pediatric patients also demonstrate a close correlation between dose per kilogram and AUC, suggesting that monitoring of ganciclovir levels may not be necessary. Based on the evidence presented in this review, routine clinical pharmacokinetic monitoring of ganciclovir does not appear to be warranted in solid organ transplant recipients.

Ocular disposition of ganciclovir and its monoester prodrugs following intravitreal administration using microdialysis

The present study was carried out to delineate the ocular pharmacokinetics of ganciclovir (GCV) following intravitreal administration. Another objective was to achieve sustained therapeutic concentrations of GCV in the vitreous over a prolonged period of time using its acyl monoester prodrugs (acetate, propionate, butyrate, and valerate). New Zealand albino male rabbits (2-2.5 kg) were kept under anesthesia. A concentric microdialysis probe was implanted in the vitreous using a 21-guage needle, and a linear microdialysis probe was implanted in the anterior chamber across the cornea using a 25-guage needle. The probes were perfused with isotonic phosphate buffer saline (pH 7.4) at a flow rate of 2 microl/min. The drugs were administered (0.2 micromoles) intravitreally and the samples were collected every 20 min over a period of 10 h. The vitreal terminal elimination half-life (t(1/2)beta) of GCV was found to be 426 +/- 109 min. The hydrolysis rate and vitreal clearance of the prodrugs increased with the ascending ester chain length. The vitreal elimination half-lives (t(1/2k10)) of GCV, acetate, propionate, butyrate, and valerate esters of GCV were 170 +/- 37, 117 +/- 50, 122 +/- 13, 55 +/- 26, and 107 +/- 14 min, respectively. A parabolic relationship was observed between the vitreal elimination rate constant and the ester chain length. Mean residence time (MRT) of the regenerated GCV following prodrug administration was found to be three to four times the value obtained after GCV injection. In conclusion, these studies have shown that the ester prodrugs generated therapeutic concentrations of GCV in vivo, and the MRT of GCV could be enhanced by 3- to 4-fold through prodrug modification.

Valacyclovir for the prevention of cytomegalovirus disease after renal transplantation. International Valacyclovir Cytomegalovirus Prophylaxis Transplantation Study Group

BACKGROUND

Cytomegalovirus (CMV) disease is a major complication of organ transplantation. We hypothesized that prophylactic treatment with valacyclovir would reduce the risk of CMV disease.

METHODS

A total of 208 CMV-negative recipients of a kidney from a seropositive donor and 408 CMV-positive recipients were randomly assigned to receive either 2 g of valacyclovir or placebo orally four times daily for 90 days after transplantation, with the dose adjusted according to renal function. The primary end point was laboratory-confirmed CMV disease in the first six months after transplantation.

RESULTS

Treatment with valacyclovir reduced the incidence or delayed the onset of CMV disease in both the seronegative patients (P<0.001) and the seropositive patients (P=0.03). Among the seronegative patients, the incidence of CMV disease 90 days after transplantation was 45 percent among placebo recipients and 3 percent among valacyclovir recipients. Among the seropositive patients, the respective values were 6 percent and 0 percent. At six months, the incidence of CMV disease was 45 percent among seronegative recipients of placebo and 16 percent among seronegative recipients of valacyclovir; it was 6 percent among seropositive placebo recipients and 1 percent among seropositive valacyclovir recipients. At six months, the rate of biopsy-confirmed acute graft rejection in the seronegative group was 52 percent among placebo recipients and 26 percent among valacyclovir recipients (P=0.001). Treatment with valacyclovir also decreased the rates of CMV viremia and viruria, herpes simplex virus disease, and the use of inpatient medical resources. Hallucinations and confusion were more common with valacyclovir treatment, but these events were not severe or treatment-limiting. The rates of other adverse events were similar among the groups.

CONCLUSIONS

Prophylactic treatment with valacyclovir is a safe and effective way to prevent CMV disease after renal transplantation.

Cytomegalovirus infection in kidney transplant patients: clinical manifestations and diagnosis

Cytomegalovirus (CMV) infection is an important cause of morbidity and mortality after solid organ transplantation. CMV infection after kidney transplantation was confirmed in 19 (54.3%) out of 35 patients. 16 of these (84.2%) developed CMV disease. CMV infection was diagnosed based on a fourfold or greater increase of anti-CMV IgG antibody titre, detection of CMV-IgM antibodies and/or virus isolation. Primary infection was observed in 3 patients, reactivation in 9 and an undefined type of infection in 7. In most patients (63%), infection was diagnosed in the first 2 months, and in 3 patients, after 3, 5 and 9 years following kidney transplantation. The most frequent symptoms of CMV disease were fever (58%), pneumonitis (26.3%) and enterocolitis (15.8%). In 53% of the patients, CMV infection co-occurred with other pathogens such as Candida albicans. Cryptococcus neoformans, bacteria or viruses (HBV, HCV, HSV). Treatment with polyvalent globulin (Sandoglobin) or hyperimmune globulin (Cytotect), in combination with ganciclovir in 7 patients, resulted in a regression of CMV disease.