Population pharmacokinetic modelling of imatinib in healthy subjects receiving a single dose of 400 mg.

PURPOSE: Imatinib is indicated for treatment of CML, GIST, etc. The population pharmacokinetics (popPK) of imatinib in patients under long-term treatment are reported in literature. Data obtained from bioequivalence trials for healthy subjects were used to evaluate the influence of demographic and pharmacogenetic factors on imatinib pharmacokinetics (PK) in a collective without concurrent drugs, organ dysfunction, inflammation etc. In addition, the differences in PK between the healthy subjects and a patient cohort was examined to identify possible disease effects. METHODS: 26 volunteers were administered orally with single dose of 400 mg imatinib. 16-19 plasma samples per volunteer were collected from 0.5 up to 72 h post-dose. The popPK was built and post hoc estimates were compared with previously published PK parameters evaluated by non-compartmental analysis in the same cohort. The predictivity of the model for data collected from 40 patients with gastrointestinal stromal tumors at steady state was evaluated. RESULTS: The popPK was best described by a two-compartment transit model with first-order elimination. No significant covariates were identified, probably due to the small cohort and the narrow range of demographic covariates; CYP3A5 phenotypes appeared to have some influence on the clearance of imatinib. Good agreement between non-compartment and popPK analyses was observed with the differences of the geometric means/ median of PK estimates below 10%. The model indicated lower clearance for patients compared to healthy volunteers (p value < 0.01). CONCLUSION: The two-compartment transit model adequately describes the absorption and distribution of imatinib in healthy volunteers. For patients, a lower clearance of imatinib compared to healthy volunteer was estimated by the model. The model can be applied for dose individualization based on trough concentrations assuming no significant differences in absorption between patients and healthy volunteers.

Effect of Cytochrome P450 and ABCB1 Polymorphisms on Imatinib Pharmacokinetics After Single-Dose Administration to Healthy Subjects.

BACKGROUND: Validated genomic biomarkers for oncological drugs are expanding to improve targeted therapies. Pharmacogenetics research focusing on the mechanisms underlying imatinib suboptimal response might help to explain the different treatment outcomes and drug safety profiles. OBJECTIVE: To investigate whether polymorphisms in genes encoding cytochrome P450 (CYP) enzymes and ABCB1 transporter affect imatinib pharmacokinetic parameters. METHODS: A prospective, multicenter, pharmacogenetic pilot study was performed in the context of two separate oral imatinib bioequivalence clinical trials, which included 26 healthy volunteers. DNA was extracted in order to analyze polymorphisms in genes CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5 and ABCB1. Imatinib plasma concentrations were measured by HPLC-MS/MS. Pharmacokinetic parameters were calculated by non-compartmental methods using WinNonlin software. RESULTS: Volunteers (n = 26; aged 24 ± 3 years; 69% male) presented regular pharmacokinetic imatinib data (concentration at 24 h, 436 ± 140 ng/mL and at 72 h, 40 ± 26 ng/mL; AUC0-72 32,868 ± 10,713 ng/mL⋅h; and Cmax 2074 ± 604 ng/mL). CYP2B6 516GT carriers showed a significant reduction of imatinib concentration at 24 h (23%, 391 ng/dL vs 511 ng/dL in 516GG carriers, p = 0.005) and elimination half-life (11%, 12.6 h vs 14.1 h in 516GG carriers, p = 0.041). Carriers for CYP3A4 (*22/*22, *1/*20 and *1/*22 variants) showed a reduced frequency of adverse events compared to *1/*1 carriers (0 vs 64%, p = 0.033). The other polymorphisms analyzed did not influence pharmacokinetics or drug toxicity. CONCLUSION: CYP2B6 G516T and CYP3A4 *20,*22 polymorphisms could influence imatinib plasma concentrations and safety profile, after single-dose administration to healthy subjects. This finding needs to be confirmed before it is implemented in clinical practice in oncological patients under treatment with imatinib.

Preferential solvation of acetaminophen in ethanol + water solvent mixtures according to the inverse Kirkwood-Buff integrals method / Solvatación preferencial del acetaminofeno en mezclas cosolventes etanol + agua según el método de las integrales inversas de Kirkwood-Buff

The preferential solvation parameters, i.e., the differences between the local mole fraction of solvents around the solute and those for the bulk co-solvent mixtures in solutions of acetaminophen in ethanol + water binary mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood-Buff integrals (IKBI) method. It is found that acetaminophen is sensitive to solvation effects, so the preferential solvation parameter δxE,A, is negative in water-rich and ethanol-rich mixtures but positive in co-solvent compositions from 0.24 to 0.73 in mole fraction of ethanol. It is conjecturable that in water-rich mixtures the hydrophobic hydration around the aromatic ring and methyl group present in the drug plays a relevant role in the solvation. The more solvation by ethanol in mixtures of similar co-solvent compositions could be due mainly to polarity effects. Finally, the preference of this drug for water in ethanol-rich mixtures could be explained in terms of the bigger acidic behavior of water molecules interacting with the hydrogen-acceptor groups present in acetaminophen such as the carbonyl group.

Con base en algunas propiedades termodinámicas clásicas de solución en este trabajo, se calcularon los parámetros de solvatación preferencial del acetaminofeno (δxE,A) en mezclas etanol + agua mediante las integrales inversas de Kirkwood-Buff. Los parámetros δxE,A corresponden a las diferencias entre las fracciones molares locales de los solventes alrededor del soluto y en el grueso de la solución. Con base en estos valores, se puede observar que este fármaco es altamente sensible a efectos específicos de solvatación que varían según la composición cosolvente. Así, los valores de δxE,A son negativos en mezclas ricas en agua y en mezclas ricas en etanol, pero positivos en composiciones desde 0,24 hasta 0,73 en fracción molar de etanol. Es probable que la hidratación hidrofóbica alrededor del anillo aromático y el grupo metilo del acetaminofeno pueda tener un papel relevante en la solvatación del fármaco en mezclas ricas de agua. En mezclas de composición intermedia, la mayor solvatación por las moléculas de etanol podría deberse principalmente a efectos de polaridad. Finalmente, la preferencia que este fármaco manifiesta por el agua en mezclas ricas en etanol podría explicarse en términos del mayor comportamiento ácido de las moléculas del agua, que estarían interactuando con los grupos aceptores de hidrógeno presentes en el acetaminofeno, tales como el carbonilo.

Randomized, Crossover and Single-Dose Bioquivalence Study of Two Oral Desogestrel Formulations (Film-Coated Tablets of 75 µg) in Healthy Female Volunteers.

Despite the increase in the substitution of branded medicinal product with generic drugs, this is a controversial issue for some pharmacological groups (such as contraceptives).The aim of the present clinical trial was to assess the bioequivalence and tolerability of two oral formulations of desogestrel.Thirty-three healthy female volunteers participated in this randomized and two-way crossover study. During two separate experimental periods, with at least four weeks of washout period, women received a single oral dose of 75 µg of desogestrel from each of the formulations (test formulation and reference formulation). Desogestrel bioavailability was determined by the measurement of 3-ketodesogestrel plasma concentration.Pharmacokinetic parameters were comparable and the 90% CI for the ratio of C(max) (96.14-114.53%) and AUC(0-t) (105.73-123.83%) values for the test and reference formulations fell within the established regulatory interval (80-125%). Both formulations were also comparable in terms of tolerability.From the results of this study it can be concluded that test formulation (desogestrel 75 µg, Cyndea PHARMA S.L.) is bioequivalent to the reference formulation (Cerazet® 75 µg, Organon Española S.A.).

Randomised, crossover clinical trial, in healthy volunteers, to compare the systemic availability of two topical intranasal budesonide formulations.

BACKGROUND: Budesonide has a long history as intranasal drug, with many marketed products. Efforts should be made to demonstrate the therapeutic equivalence and safety comparability between them. Given that systemic availability significantly varies from formulations, the clinical comparability of diverse products comes to be of clinical interest and a regulatory requirement. The aim of the present study was to compare the systemic availability, pharmacodynamic effect, and safety of two intranasal budesonide formulations for the treatment of rhinitis. METHODS: Eighteen healthy volunteers participated in this randomised, controlled, crossover, clinical trial. On two separated days, subjects received a single dose of 512 mug budesonide (4 puffs per nostril) from each of the assayed devices (Budesonida nasal 64(R), Aldo-Union, Spain and Rhinocort 64(R), AstraZeneca, Spain). Budesonide availability was determined by the measurement of budesonide plasma concentration. The pharmacodynamic effect on the hypothalamic-adrenal axis was evaluated as both plasma and urine cortisol levels. Adverse events were tabulated and described. Budesonide availability between formulations was compared by the calculation of 90%CI intervals of the ratios of the main pharmacokinetic parameters describing budesonide bioavailability. Plasma cortisol concentration-time curves were compared by means of a GLM for Repeated Measures. Urine cortisol excretion between formulations was compared through the Wilcoxon's test. RESULTS: All the enrolled volunteers successfully completed the study. Pharmacokinetic parameters were comparable in terms of AUC(t) (2.6 +/- 1.5 vs 2.2 +/- 0.7), AUC(i) (2.9 +/- 1.5 vs 2.4 +/- 0.7), t(max) (0.4 +/- 0.1 vs 0.4 +/- 0.2), C(max)/AUC(i) (0.3 +/- 0.1 vs 0.3 +/- 0.0), and MRT (5.0 +/- 1.4 vs 4.5 +/- 0.6), but not in the case of C(max) (0.9 +/- 0.3 vs 0.7 +/- 0.2) and t(1/2) (3.7 +/- 1.8 vs 2.9 +/- 0.4). The pharmacodynamic effects, measured as the effect over plasma and urine cortisol, were also comparables between both formulations. No severe adverse events were reported and tolerance was comparable between formulations. CONCLUSION: The systemic availability of intranasal budesonide was comparable for both formulations in terms of most pharmacokinetic parameters. The pharmacodynamic effect on hypothalamic-pituitary-adrenal axis was also similar. Side effects were scarce and equivalent between the two products. This methodology to compare different budesonide-containing devices is reliable and easy to perform, and should be recommended for similar products intented to be marketed or already on the market. TRIAL REGISTRATION: No Eudra CT: 2005-003727-39.