Background: Ganciclovir and valganciclovir are used for prophylaxis and treatment of cytomegalovirus infection. However, there is great interindividual variability in ganciclovir’s pharmacokinetics (PK), highlighting the importance of individualized dosing. To facilitate model-informed precision dosing (MIPD), this study aimed to establish a parametric model repository of ganciclovir and valganciclovir by summarizing existing population pharmacokinetic information and analyzing the sources of variability. (2) Methods: A total of four databases were searched for published population PK models. We replicated these models, evaluated the impact of covariates on clearance, calculated the probability of target attainment for each model based on a predetermined dosing regimen, and developed an area under the concentration–time curve (AUC) calculator using maximum a posteriori Bayesian estimation. (3) Results: A total of 16 models, one- or two-compartment models, were included. The most significant covariates were body size (weight and body surface area) and renal function. The results show that 5 mg/kg/12 h of ganciclovir could make the AUC_0–24h within 40–80 mg·h/L for 50.03% pediatrics but cause AUC_0–24h exceeding the exposure thresholds for toxicity (120 mg·h/L) in 51.24% adults. (4) Conclusions: Dosing regimens of ganciclovir and valganciclovir should be adjusted according to body size and renal function. This model repository has a broad range of potential applications in MIPD.

Background: Caspofungin is an echinocandin antifungal agent commonly used as the first-line therapy for invasive candidiasis, salvage therapy for invasive aspergillosis, and empirical therapy for presumed fungal infections. Pharmacokinetic (PK) variabilities and suboptimal exposure have been reported for caspofungin, increasing the risk of insufficient efficacy. Objective: This work aimed to develop a caspofungin population pharmacokinetic (popPK) library and demonstrate its utility by assessing the probability of target attainment across diverse settings. Methods: We established a caspofungin popPK model library following a rigorous literature review, re-implementing selected models in R with rxode2. Quality control procedures included a comparison of different studies and assessing covariate impacts. Model libraries were primarily used to perform Monte Carlo simulations to estimate target attainment and guide personalized dosing in Candida infections. Results: A total of 13 models, one- or two-compartment models, were included. The most significant covariates were body size (weight and body surface area), liver function, and albumin level. The results show that children and adults showed considerable differences in pharmacokinetics. For C. albicans and C. parapsilosis, none of the populations achieved a PTA of ≥90% at their respective susceptible MIC values. In contrast, for C. glabrata, 70% of the adult studies reached a PTA of ≥90%, while all pediatric studies achieved the same PTA level. Conclusion: At the recommended dosage, adult patients showed notably lower exposure to caspofungin compared to pediatric patients. Considering body size, liver function, and serum albumin is crucial when determining caspofungin dosage regimens. Furthermore, further research is required to comprehensively understand the pharmacokinetics of caspofungin in pediatric patients.

Intravenous ganciclovir (GCV) is used for the treatment of cytomegalovirus (CMV) infection in immunocompromised children. Although the therapeutic target for treatment is unclear, studies have shown a serum area under the concentration–time curve (AUC _24h ) ≥40 mg/L·h correlates with effective CMV prevention. This study aimed to externally validate existing GCV population pharmacokinetic (PopPK) models and develop a model if needed and evaluate the serum AUC _24h achieved with standard GCV dosing and propose an optimized dosing strategy for immunocompromised children. Ganciclovir drug monitoring data from two pediatric hospitals were retrospectively collected, and published pediatric PopPK models were externally validated. The population AUC _24h with standard GCV dosing (5 mg/kg twice daily) was calculated, and an optimized dosing strategy was determined using Monte Carlo simulations to achieve an AUC _24h between 40 and 100 mg/L·h. Overall, 161 samples from 23 children with a median (range) age of 9.0 years (0.4–17.0) and weight of 28.2 kg (5.6–73.3) were analyzed. Transferability of published pediatric PopPK models was limited. Thus, a one-compartment model with first-order absorption and elimination with weight and serum creatinine as covariates was developed. The median (5th–95th percentiles) steady state AUC _24h with standard dosing was 38.3 mg/L·h (24.8–329.2) with 13 children having an AUC _24h <40 mg/L·h, particularly those aged <4 years (8/13). An optimized simulated GCV dosing regimen, ranging from 2 to 13 mg/kg twice daily for children with normal renal function, achieved 61%–78% probability of target attainment. Standard GCV dosing likely results in inadequate drug exposure in more than half of the children, particularly those aged <4 years. An optimized dosing regimen has been proposed for clinical validation.

Objective: Isoniazid exposure in vivo is significantly affected by NAT2 genotypes and has ethnic differences. To optimize the sampling strategy for isoniazid in East Asian pediatric populations. We employed a model-informed optimization approach based on INH population pharmacokinetic (PopPK) models. Methods: We selected PopPK models for children and East Asian adults and optimized the sampling strategy using PopED (Population Experimental Design), a method that helps identify the most efficient sampling points for maximizing parameter estimation accuracy. Virtual patients with varying NAT2 phenotypes were created, and real-world pediatric scenarios were evaluated using questionnaire data, sampling windows, and stochastic simulations. Results: From eight analyzed models (four for East Asian adults and four for non-East Asian pediatrics), we simplified two over-parameterized models using lumping without loss of performance. The optimized clinical sampling strategy involved collecting samples at 0.25 [0– 0.5], 1.5 [1– 2], 6 [3– 8], 12 [9– 14], and 24 [22– 24] hours post-dose. Simulation verification showed that re-estimated major PK parameters had acceptable relative biases and relative standard error (< 30%). Conclusion: Traditional adult sampling strategies are inadequate for East Asian pediatric populations. A tailored strategy involving up to five samples can accurately estimate INH PopPK parameters and should be considered for clinical implementation to optimize treatment and reduce patient sampling burden.

Caspofungin is an echinocandin antifungal commonly used as the first-line therapy for invasive candidiasis, salvage therapy for invasive aspergillosis. Pharmacokinetic variabilities and suboptimal exposure have been reported for caspofungin, increasing the risk of insufficient efficacy. We aimed to consolidate information from population pharmacokinetic studies, compare model performance, identify significant covariates affecting caspofungin’s PKs, evaluate probability of target attainment in different studies and assemble pharmacokinetic/pharmacodynamic target to address existing knowledge gaps that may warrant further investigation in future. We performed a systematic search strategy to review the PPK studies of caspofungin. Four databases were searched. We extracted information for the comparison of models, evaluation of the impact of covariates on clearance and apparent volume and the calculation of probability of target attainment under specific minimum inhibitory concentration. Thirteen studies were included. The simulation results showed that under labeled dose, pediatrics exhibited notably higher exposure than adults. Body size was the most identified covariate that affected both clearance and volume of distribution. For C. albicans and C. parapsilosis, none of the populations achieved a PTA of ≥ 90%. In contrast, for C. glabrata, 70% of the adult patients reached a PTA of ≥ 90%, while all pediatric patients achieved the same PTA level. At the recommended dosage, adults showed lower exposure to caspofungin compared to pediatrics. It is crucial to consider body size, liver function and serum albumin when determining caspofungin dosage regimens. Furthermore, further research is required to comprehensively understand the pharmacokinetics of caspofungin in pediatrics.