Model-based meta-analysis of salbutamol pharmacokinetics and practical implications for doping control.

Salbutamol was included in the prohibited list of the World Anti-Doping Agency (WADA) in 2004. Although systemic intake is banned, inhalation for asthma is permitted but with dosage restrictions. The WADA established a urinary concentration threshold to distinguish accordingly prohibited systemic self-administration from therapeutic prescription by inhalation. This study aimed at evaluating the ability of the WADA threshold to differentiate salbutamol therapeutic use from violation of antidoping rules. Concentration-time profile of salbutamol in plasma and its excretion in urine was characterized through a model-based meta-analysis of individual and aggregate data collected after administration of a large range of doses following different modes of administration and under a variety of conditions. The developed model adequately fitted salbutamol plasma and urine concentration-time profiles of the 13 selected studies. Model-based simulations confirmed that a wide range of salbutamol urine concentrations might be measured after drug intake. Although violation of the WADA Code can be strongly suspected in individuals showing very high salbutamol urine concentrations, uncertainty remains for values close to the WADA threshold as they can be compatible with both permitted therapeutic use and violation. Although not entirely discriminant, the current WADA rule is globally supported by our appraisal. It could be further improved by a slight and reasonable adjustment of inhaled daily dosages allowed for therapeutic use. Our model might help antidoping experts in the evaluation of suspected doping cases through confronting the athlete's urine measurements with their allegations about salbutamol treatment

Physiologically‐Based Pharmacokinetic Modeling Combined with Swiss HIV Cohort Study Data Supports No Dose Adjustment of Bictegravir in Elderly Individuals Living With HIV

Clinical studies in aging people living with HIV (PLWH) are sparse for the novel integrase inhibitor bictegravir, leading to some uncertainty about dosing recommendations for elderly PLWH. The objective of this study was to investigate the continuous impact of aging on bictegravir pharmacokinetics by combining clinically observed data with modeling to support a safe and efficient anti-HIV therapy with advanced age. A physiologically-based pharmacokinetic (PBPK) model was developed for bictegravir with clinically observed data from phase I studies. The predictive model performance was verified using bictegravir plasma concentrations sampled as part of the general therapeutic drug monitoring (TDM) program of the Swiss HIV Cohort Study in young (20-55 years) and elderly PLWH (55-85 years). The verified PBPK model subsequently predicted the continuous impact of aging on bictegravir pharmacokinetics across adulthood (20-99 years). Bictegravir exposure was unchanged in elderly compared with young PLWH when analyzing the TDM data of the Swiss HIV Cohort Study. PBPK simulations predicted clinically observed data from 60 young and 32 elderly PLWH mostly within the 95% confidence interval, demonstrating the predictive power of the used modeling approach. Simulations predicted drug exposure to increase up to 40% during adulthood, which was not statistically significantly different from the age-related pharmacokinetic changes of other HIV and non-HIV drugs. Sex had no impact on the age-related changes of bictegravir pharmacokinetics. Considering the safety margin of bictegravir, a dose adjustment for the novel integrase inhibitor is a priori not necessary in elderly PLWH in the absence of severe comorbidities

UHPLC-MS/MS assay for simultaneous determination of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin with its active metabolites in human plasma, for population-scale drug-drug interactions studies in people living with HIV.

Thanks to highly active antiretroviral treatments, HIV infection is now considered as a chronic condition. Consequently, people living with HIV (PLWH) live longer and encounter more age-related chronic co-morbidities, notably cardiovascular diseases, leading to polypharmacy. As the management of drug-drug interactions (DDIs) constitutes a key aspect of the care of PLWH, the magnitude of pharmacokinetic DDIs between cardiovascular and anti-HIV drugs needs to be more thoroughly characterized. To that endeavour, an UHPLC-MS/MS bioanalytical method has been developed for the simultaneous determination in human plasma of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin and its active metabolites. Plasma samples were subjected to protein precipitation with methanol, followed by evaporation at room temperature under nitrogen of the supernatant, allowing to attain measurable plasma concentrations down to sub-nanogram per milliliter levels. Stable isotope-labelled analytes were used as internal standards. The five drugs and two metabolites were analyzed using a 6-min liquid chromatographic run coupled to electrospray triple quadrupole mass spectrometry detection. The method was validated over the clinically relevant concentrations ranging from 0.3 to 480 ng/mL for amlodipine, atorvastatin and p-OH-atorvastatin, and 0.4 to 480 ng/mL for pravastatin, 0.5 to 480 ng/mL for rosuvastatin and o-OH-atorvastatin, and 3 to 4800 ng/mL for metoprolol. Validation performances such as trueness (95.4-110.8%), repeatability (1.5-13.4%) and intermediate precision (3.6-14.5%) were in agreement with current international recommendations. Accuracy profiles (total error approach) were lying within the limits of ±30% accepted in bioanalysis. This rapid and robust UHPLC-MS/MS assay allows the simultaneous quantification in plasma of the major currently used cardiovascular drugs and offers an efficient analytical tool for clinical pharmacokinetics as well as DDIs studies

Population pharmacokinetic modelling to characterize the effect of chronic kidney disease on tenofovir exposure after tenofovir alafenamide administration.

Tenofovir alafenamide is gradually replacing tenofovir disoproxil fumarate, both prodrugs of tenofovir, in HIV prevention and treatment. There is thus an interest in describing tenofovir pharmacokinetics (PK) and its variability in people living with HIV (PLWH) under tenofovir alafenamide in a real-life setting. To characterize the usual range of tenofovir exposure in PLWH receiving tenofovir alafenamide, while assessing the impact of chronic kidney disease (CKD). We conducted a population PK analysis (NONMEM®) on 877 tenofovir and 100 tenofovir alafenamide concentrations measured in 569 PLWH. Model-based simulations allowed prediction of tenofovir trough concentrations (Cmin) in patients having various levels of renal function. Tenofovir PK was best described using a one-compartment model with linear absorption and elimination. Creatinine clearance (CLCR, estimated according to Cockcroft and Gault), age, ethnicity and potent P-glycoprotein inhibitors were statistically significantly associated with tenofovir clearance. However, only CLCR appeared clinically relevant. Model-based simulations revealed 294% and 515% increases of median tenofovir Cmin in patients with CLCR of 15-29 mL/min (CKD stage 3), and less than 15 mL/min (stage 4), respectively, compared with normal renal function (CLCR = 90-149 mL/min). Conversely, patients with augmented renal function (CLCR > 149 mL/min) had a 36% decrease of median tenofovir Cmin. Kidney function markedly affects circulating tenofovir exposure after tenofovir alafenamide administration in PLWH. However, considering its rapid uptake into target cells, we suggest only a cautious increase of tenofovir alafenamide dosage intervals to 2 or 3 days only in case of moderate or severe CKD, respectively

Population pharmacokinetic modelling to quantify the magnitude of drug-drug interactions between amlodipine and antiretroviral drugs.

Drug-drug interactions (DDIs) with antiretroviral drugs (ARVs) represent an important issue in elderly people living with HIV (PLWH). Amlodipine is a commonly prescribed antihypertensive drug metabolized by CYP3A4, thus predisposed to a risk of DDIs. Guidance on the management of DDIs is mostly based on theoretical considerations derived from coadministration with other CYP3A4 inhibitors. This study aimed at characterizing the magnitude of DDIs between amlodipine and ARV drugs in order to establish dosing recommendations. A population pharmacokinetic analysis was developed using non-linear mixed effect modelling (NONMEM) and included 163 amlodipine concentrations from 55 PLWH. Various structural and error models were compared to characterize optimally the concentration-time profile of amlodipine. Demographic and clinical characteristics as well as comedications were tested as potential influential covariates. Model-based simulations were performed to compare amlodipine exposure (i.e. area under the curve, AUC) between coadministered ARV drugs. Amlodipine concentration-time profile was best described using a one-compartment model with first-order absorption and a lag-time. Amlodipine apparent clearance was influenced by both CYP3A4 inhibitors and efavirenz (CYP3A4 inducer). Model-based simulations revealed that amlodipine AUC increased by 96% when coadministered with CYP3A4 inhibitors, while efavirenz decreased drug exposure by 59%. Coadministered ARV drugs significantly impact amlodipine disposition in PLWH. Clinicians should adjust amlodipine dosage accordingly, by halving the dosage in PLWH receiving ARV with inhibitory properties (mainly ritonavir-boosted darunavir), whereas they should double amlodipine doses when coadministering it with efavirenz, under appropriate monitoring of clinical response and tolerance