Population pharmacokinetic modelling of intravenous immunoglobulin in patients with predominantly antibody deficiencies.

AIMS: There is considerable interpatient variability in the pharmacokinetics (PK) of intravenous immunoglobulin G (IVIG), causing difficulty in optimizing individual dosage regimen. This study aims to estimate the population PK parameters of IVIG and to investigate the impact of genetic polymorphism of the FcRn gene and clinical variability on the PK of IVIG in patients with predominantly antibody deficiencies. METHODS: Patients were recruited from four hospitals. Clinical data were recorded and blood samples were taken for PK and genetic studies. Population PK parameters were estimated by nonlinear mixed-effects modelling in Monolix®. Models were evaluated using the difference in objective function value, goodness-of-fit plots, visual predictive check and bootstrap analysis. Monte Carlo simulation was conducted to evaluate different dosing regimens for IVIG. RESULTS: A total of 30 blood samples were analysed from 10 patients. The immunoglobulin G concentration data were best described by a one-compartment model with linear elimination. The final model included both volume of distribution (Vd) and clearance (CL) based on patient's individual weight. Goodness-of-fit plots indicated that the model fit the data adequately, with minor model mis-specification. Genetic polymorphism of the FcRn gene and the presence of bronchiectasis did not affect the PK of IVIG. Simulation showed that 3-4-weekly dosing intervals were sufficient to maintain IgG levels of 5 g L-1 , with more frequent intervals needed to achieve higher trough levels. CONCLUSIONS: Body weight significantly affects the PK parameters of IVIG. Genetic and other clinical factors investigated did not affect the disposition of IVIG.

A Systematic Review and Meta-regression Analysis on the Impact of Increasing IgG Trough Level on Infection Rates in Primary Immunodeficiency Patients on Intravenous IgG Therapy.

PURPOSE: We conducted a systematic review and meta-regression analysis to evaluate the impact of increasing immunoglobulin G (IgG) trough levels on the clinical outcomes in patients with PID receiving intravenous immunoglobulin G (IVIG) treatment. METHODS: Systematic search was conducted in PubMed and Cochrane. Other relevant articles were searched by reviewing the references of the reviewed article. All clinical trials with documented IgG trough levels and clinical outcome of interest in patients receiving IVIG treatment were eligible to be included in this review. Meta-regression analysis was conducted using Comprehensive Meta-analysis Software. Additional sensitivity analyses were undertaken to evaluate the robustness of the overall results. RESULTS: Twenty-eight clinical studies with 1218 patients reported from year 2001 to 2018 were included. The mean IVIG dose used ranges from 387 to 560 mg/kg every 3 to 4 weekly, and mean IgG trough obtained ranges from 660 to 1280 mg/dL. Random-effects meta-regression slope shows that IgG trough level increases significantly by 73 mg/dL with every increase of 100 mg/kg dose of IVIG (p < 0.05). Overall infection rates reduced significantly by 13% with every increment of 100 mg/dL of IgG trough up to 960 mg/dL (p < 0.05). CONCLUSION: This meta-analysis concludes that titrating the IgG trough levels up to 960 mg/dL progressively reduces the rate of infections, and there is less additional benefit beyond that. Further studies to validate this result are required before it can be used in clinical practice.

Prescribing Practices of Intravenous Immunoglobulin in Tertiary Care Hospitals in Malaysia: A Need for a National Guideline for Immunoglobulin Use.

Rational use of drug involves the use of medicine as per clinical guidelines. Given the steady increase in the clinical utility of intravenous immunoglobulin (IVIG) either as licensed or off-label use, concerns are being raised about the possibility of supply shortages that could significantly impact patient care. Therefore, there is a need to regulate and to promote the rational use of this valuable medication. This cross-sectional chart review study attempts to evaluate the prescribing patterns of IVIG at two tertiary hospitals in Malaysia. Patients' medical files and dispensing records were examined and compared with current guidelines. A total of 348 prescriptions for IVIG were written during the 1-year study period. The highest usage of IVIG was for neurological (47.9%), immunological (27.5%), and hematological conditions (20%). The number of prescriptions with the US Food and Drug Administration (FDA) licensed indications and off-label indications was 148 (42.5%) and 200 (57.5%), respectively. Age (OR: 1.02, 95% CI: 1.01-1.03, p = 0.003) and those admitted to the critical care units (OR: 11.11, 95% CI: 5.60-22.05, p < 0.001) were significant factors for receiving IVIG for an off-label indication. Most prescriptions (79%) had appropriate dosing. Significant factors associated with receiving inappropriate dose of IVIG include age (OR: 0.93, 95% CI: 0.89-0.97, p = 0.001) and those admitted to the critical care units (OR: 10.15, 95% CI: 3.81-27.06, p < 0.001). This study advocates the development and implementation of evidence-based clinical guidelines with prioritization protocol to ensure rational use of IVIG.

A systematic review of population pharmacokinetic analyses of polyclonal immunoglobulin G therapy.

BACKGROUND: Population pharmacokinetics (popPK) using the nonlinear mixed-effect (NLME) modeling approach is an essential tool for guiding dose individualization. Several popPK analyses using the NLME have been conducted to characterize the pharmacokinetics of immunoglobulin G (IgG). OBJECTIVE: To summarize the current information on popPK of polyclonal IgG therapy. METHOD: A systematic search was conducted in the PubMed and Web of Science databases from inception to December 2020. Additional relevant studies were also included by reviewing the reference list of the reviewed articles. All popPK studies that employed the NLME modeling approach were included and data were synthesized descriptively. RESULTS: This review included seven studies. Most of the popPK models were developed in patients with primary immunodeficiency (PID). IgG pharmacokinetics was described as a two-compartment model in five studies, while it was described as a one-compartment model in two other studies. Among all tested covariates, weight was consistently identified as a significant predictor for clearance (CL) of IgG. Whereas, weight and disease type were found to be significant predictors for the volume of distribution in central compartment (Vc). In a typical 70 kg adult, the median estimated values of Vc and CL were 4.04 L and 0.144 L/day, respectively. The between subject variability of Vc was considered large. Only two studies evaluated their models using external data. CONCLUSIONS: Seven popPK studies of IgG were found and discussed, with only weight being a significant covariate across all studies. Future studies linking pharmacokinetics with pharmacodynamics in PID and other patient populations are required.

Prescribing errors in pediatric outpatient department at a tertiary care hospital in Malaysia.

Background Prescribing errors in children are common due to individualization of dosage regimen. It potentially has a great impact especially in this vulnerable population. Objective To determine the prevalence and common types of prescribing errors in a Malaysian pediatric outpatient department and to determine the factors contributing to prescribing errors. Setting Pediatric Outpatient Department and Outpatient Pharmacy at a tertiary care hospital in Malaysia. Method This is a prospective, cross sectional observational study where all new prescriptions received by the outpatient pharmacy from patients attending pediatric out-patient clinic were included for analysis. Descriptive statistics and logistic regression were used to analyze the data. Main outcome measure Frequency, types, potential clinical consequences and contributing factors of prescribing errors. Results Two hundred and fifty new prescriptions with 493 items were analyzed. There were 13 per 100 prescriptions with at least one prescribing error and 7.3% of the total items were prescribed incorrectly. The most common types of prescribing error were, an ambiguous prescription (61.1%) followed by an unrecommended dose regimen (13.9%). Logistic regression analysis showed that the risk of a prescribing error significantly increased when the prescription was written by a house officer (OR 4.72, p = 0.029). Errors were judged to be potentially non-significant (33.3%), significant (36.1%), or serious (30.6%). Conclusion The experience of prescribers is an important factor that contributes to prescribing errors in pediatrics. Many of the errors made were potentially serious and may impact on the patients' well-being.

Unlicensed and off-label use of medicines in children admitted to the intensive care units of a hospital in Malaysia.

BACKGROUND: Unlicensed and off-label use of medicines in paediatrics is widespread. However, the incidence of this practice in Malaysia has not been reported. OBJECTIVE: To determine the extent of unlicensed and off-label use of medicines in hospitalised children in the intensive care units of a tertiary care teaching hospital. METHODS: A prospective, observational exploratory study was conducted on medicines prescribed to children admitted to the 3 intensive care units of Universiti Kebangsaan Malaysia Medical Centre (UKMMC). RESULTS: A total of 194 patients were admitted to UKMMC, 168 of them received one or more drugs. Of 1,295 prescriptions, 353 (27.3 %) were unlicensed and 442 (34.1 %) were for off-label use. Forty-four percent of patients received at least one medicine for unlicensed use and 82.1 % received at least one medicine off-label. Preterm infants, children aged 28 days to 23 months, patients with hospital stays of more than 2 weeks, and those prescribed increasing numbers of medicines were more likely to receive medicines for unlicensed use. Term neonates and patients prescribed increasing numbers of medicines had increased risk of receiving medicines for off-label use. CONCLUSION: Prescribing of medicines in an unlicensed or off-label fashion to the children in the intensive care units of UKMMC was common. Further detailed studies are necessary to ensure the delivery of safe and effective medicines to children.