Therapeutic Drug Monitoring of Ganciclovir: Where Are We?

BACKGROUND: Ganciclovir is the mainstay of therapy for the prophylaxis and treatment of Cytomegalovirus. However, therapy with this antiviral agent is hindered by side effects such as myelosuppression, which often leads to therapy cessation. Underdosing, as an attempt to prevent side effects, can lead to drug resistance and therapy failure. Therapeutic drug monitoring (TDM) has been used to overcome these problems. The purpose of this narrative review was to give an overview of ganciclovir TDM, available assays, population pharmacokinetic models, and discuss the current knowledge gaps. METHODS: For this narrative review, a nonsystematic literature search was performed on the PubMed database in April 2021. The following search terms were used: ganciclovir, valganciclovir, pharmacokinetics, pharmacodynamics, population pharmacokinetics, therapeutic drug monitoring, bioassay, liquid chromatography coupled with tandem mass spectrometry, liquid chromatography, chromatography, spectrophotometry, and toxicity. In addition, the reference lists of the included articles were screened. RESULTS: The most common bioanalysis method identified was liquid chromatography coupled with tandem mass spectrometry. There are different models presenting ganciclovir IC50; however, establishing a pharmacokinetic/pharmacodynamic target for ganciclovir based on preclinical data is difficult because there are no studies combining dynamic drug exposure in relation to inhibition of viral replication. The data on ganciclovir TDM show large interindividual variability, indicating that TDM may play a role in modifying the dose to reduce toxicity and prevent treatment failure related to low concentrations. The main hurdle for implementing TDM is the lack of robust data to define a therapeutic window. CONCLUSIONS: Although the pharmacokinetics (PK) involved is relatively well-described, both the pharmacodynamics (PD) and pharmacokinetic/pharmacodynamic relationship are not. This is because the studies conducted to date have mainly focused on estimating ganciclovir exposure, and owing to the limited therapeutic options for CMV infections, future studies on ganciclovir are warranted.

Ganciclovir therapeutic drug monitoring in transplant recipients.

BACKGROUND: The use of (val)ganciclovir is complicated by toxicity, slow response to treatment and acquired resistance. OBJECTIVES: To evaluate a routine therapeutic drug monitoring (TDM) programme for ganciclovir in a transplant patient population. METHODS: An observational study was performed in transplant recipients from June 2018 to February 2020. Dose adjustments were advised by the TDM pharmacist as part of clinical care. For prophylaxis, a trough concentration (Cmin) of 1-2 mg/L and an AUC24h of >50 mg·h/L were aimed for. For treatment, a Cmin of 2-4 mg/L and an AUC24h of 80-120 mg·h/L were aimed for. RESULTS: Ninety-five solid organ and stem cell transplant patients were enrolled. Overall, 450 serum concentrations were measured; with a median of 3 (IQR = 2-6) per patient. The median Cmin and AUC24h in the treatment and prophylaxis groups were 2.0 mg/L and 90 mg·h/L and 0.9 mg/L and 67 mg·h/L, respectively. Significant intra- and inter-patient patient variability was observed. The majority of patients with an estimated glomerular filtration rate of more than 120 mL/min/1.73 m2 and patients on continuous veno-venous haemofiltration showed underexposure. The highest Cmin and AUC24h values were associated with the increase in liver function markers and decline in WBC count as compared with baseline. CONCLUSIONS: This study revealed that a standard weight and kidney function-based dosing regimen resulted in highly variable ganciclovir Cmin and under- and over-exposure were observed in patients on dialysis and in patients with increased renal function. Clearly there is a need to explore the impact of concentration-guided dose adjustments in a prospective study.

Acute and Subchronic Oral Toxicity Evaluation of Herbal Formulation: Piper crocatum Ruiz and Pav., Typhonium flagelliforme (Lodd.) Blume, and Phyllanthus niruri L. in Sprague-Dawley Rats.

Background: The product combination of Piper crocatum Ruiz. and Pav., Phyllanthus niruri Linn., and Typhonium flagelliforme (Lodd.) BL ethanolic extract (SKM) exerts immunomodulatory activity. However, the toxicity profile of the combination has never been investigated. Objective: This study aimed to establish the acute toxicity profile of the SKM product on Sprague-Dawley (SD) rats and its subchronic toxicity profile on female SD rats. Method: The acute and subchronic toxicity tests were conducted in accordance with OECD 423 and OECD 408, respectively. Result: The SKM product was safe up to 5000 mg/kg b.w. in male and female SD rats. In repeated doses of SKM for 90 days, the administration of 22.5, 45, and 90 mg/kg b.w. per day of the SKM product to female SD rats did not affect clinical signs, body weight, food and water consumption, hematological parameters, clinical chemical parameters, urinalysis, relative organ weights, and gross pathological and histopathological features compared with the control group. Conclusion: Analyses of these results suggest that the long-term oral administration of the SKM product for 90 days does not cause subchronic toxicity.