Synchronous Spectrofluorimetry Coupled with Third-Order Derivative Signal Processing for the Simultaneous Quantitation of Telmisartan and Chlorthalidone Drug Combination in Human Plasma.

This study is the first to develop and optimize a method for the simultaneous determination of chlorthalidone (CLT) and telmisartan (TEL) in, human plasma samples as well as in their newly released pharmaceutical tablet form, (Telmikind-CT 40®). The method is based on measuring fluorescence intensity, employing synchronous fluorescence mode coupled to third-order derivative signal processing, 0.5% w/v cetyl trimethyl ammonium bromide was used as cationic surfactant to enhance the fluorescence signal intensity and improve method sensitivity. The third-order derivative synchronous spectra of CLT and TEL are well separated with two zero-crossing points which allowed for the determination of CLT and TEL at 362 nm and 351 nm, respectively. Different experimental parameters were carefully investigated and optimized, calibration curves were constructed over concentration ranges of 20-1200 ng.mL-1 and 5-800 ng.mL-1 for CLT and TEL respectively. The developed method is simple and rapid, analytical parameters were validated according to ICH guidelines and high sensitivity was achieved as represented by limits of detection (LOD) of 4.69 and 1.58 ng.mL-1 for CLT and TEL respectively.

Supersaturable self-microemulsifying drug delivery system enhances dissolution and bioavailability of telmisartan.

To enhance the dissolution and oral bioavailability of telmisartan (TMS), a poorly water-soluble anti-hypertensive drug, a supersaturable self-microemulsifying drug delivery system (SuSMEDDS) was developed. Amorphous alkalinized TMS (AAT) was formulated into a SMEDDS, composed of Capmul® MCM (oil), Cremophor® RH40 (surfactant), and tetraglycol (co-surfactant). Although the SMEDDS was rapidly dissolved (>80% within 5 min) in a limited condition (500 mL, pH 6.8), drug precipitation was observed over time, resulting in a decrease in dissolution levels. The precipitation was due to drug recrystallization, as determined by differential scanning calorimetry and powder X-ray diffraction analyses. Several polymers, including Soluplus® (SOL), were screened as precipitation inhibitors; ultimately, SuSMEDDS-SOL was prepared by admixing SOL and the SMEDDS at a 5:100 (w/w) ratio. SuSMEDDS-SOL was superior in terms of dissolution efficiency (>90% over 2 h) and dissolution-retaining time (no precipitation over 2 h). An in vivo pharmacokinetic study in rats revealed that the oral bioavailability of SuSMEDDS-SOL was 4.8-, 1.3-, and 1.2-fold greater than those of the TMS suspension, AAT solution, and SMEDDS, respectively. Therefore, SuSMEDDS-SOL is a promising candidate to enhance the dissolution and oral bioavailability of TMS.

Predicted values for human total clearance of a variety of typical compounds with differently humanized-liver mouse plasma data.

Prediction of human pharmacokinetics is important in the preclinical stage. Values for total clearance of compounds from plasma should be one of the most important pharmacokinetic parameters for predictions. Although several physiological and empirical methods including single-species allometry for prediction of values for human clearance of compounds using humanized-liver mice have been reported, further improvement of prediction accuracies would be still expected. To optimize these approaches, we proposed methods for unbound intrinsic clearance in virtually 100% humanized-liver mouse by incorporating unbound plasma fractions of compounds in differently humanized-liver mice. Comparisons of prediction accuracies of values for human clearance of 15 model compounds were performed among our current physiological and previously reported models and single-species allometry using humanized-liver mice. Incorporation of the actual unbound plasma fractions of compounds and correction of residual mice hepatocyte in humanized-liver mice showed comparable prediction accuracy to that by single-species allometry. After exclusion of 3 compounds with large species differences in values of clearance and unbound plasma fractions between mice and humans out of 15 compounds, prediction accuracies were improved in the methods investigated. The previously and present reported physiological methods could show the good prediction accuracy of values for clearance of drugs from plasma.

UGT1A3 and Sex Are Major Determinants of Telmisartan Pharmacokinetics-A Comprehensive Pharmacogenomic Study.

To investigate how variability in multiple pharmacokinetic genes associates with telmisartan exposure, we determined telmisartan single-dose (40 mg) pharmacokinetics and sequenced 379 genes in 188 healthy volunteers. Intronic UGT1A variants showed the strongest associations with the area under the plasma concentration-time curve from zero hours to infinity (AUC0-∞ ) and peak plasma concentration (Cmax ) of telmisartan. These variants were strongly linked with the increased function UGT1A3*2 allele, suggesting that it is the causative allele underlying these associations. In addition, telmisartan plasma concentrations were lower in men than in women. The UGT1A3*2 was associated with a 64% and 63% reduced AUC0-∞ of telmisartan in UGT1A3*2 heterozygous and homozygous men, respectively (P = 1.21 × 10-16 and 5.21 × 10-8 ). In women, UGT1A3*2 heterozygosity and homozygosity were associated with 57% (P = 1.54 × 10-11 ) and 72% (P = 3.31 × 10-15 ) reduced AUC0-∞ , respectively. Furthermore, a candidate gene analysis suggested an association of UGT1A3*3 and the SLCO1B3 c.767G>C missense variant with telmisartan pharmacokinetics. A genotype score, which reflects the effects of sex and genetic variants on telmisartan AUC0-∞ , associated with the effect of telmisartan on diastolic blood pressure. These data indicate that sex and UGT1A3 are major determinants and suggest a role for OATP1B3 in telmisartan pharmacokinetics.

Proniosomal Telmisartan Tablets: Formulation, in vitro Evaluation and in vivo Comparative Pharmacokinetic Study in Rabbits.

OBJECTIVE: The purpose of this study was to prepare proniosomal vesicles of Telmisartan (TEL) to be compressed into tablets which will be further evaluated in vitro and in vivo. MATERIALS AND METHODS: An experimental design was adopted using surfactants of different HLB values (span 40-brij 35), different cholesterol ratios (20-50%) and different phospholipid types (egg yolk-soyabean). Different responses were measured followed by tablet manufacturing. The highest EE was shown in F3 (85%) while the lowest value was obtained in F7 (8.4%). Finally, zeta potential results were in the range of -0.67 to -27.6 mv. Compressibility percent revealed that F5 showed an excellent flowability characteristic with a value of 9.74±1.61 while F3 and F6 showed good flowability characteristics. By the end of the release, F6 showed approximately 90% drug release. RESULTS: F6 was selected for the in vivo study; Cmax was increased by 1.5-fold while AUC0-∞ also increased significantly by 3-fold when compared with commercial tablet and finally, tmax was increased by 3-fold indicating sustained release pattern. The relative bioavailability was also increased by 3.2-fold. CONCLUSION: The results of this study suggested that the formulation of compressed tablets containing more stable proniosomal powder extended the release of TEL and increased its bioavailability as well.

Pharmacokinetic interactions between telmisartan/amlodipine and rosuvastatin after multiple oral administrations in healthy Korean male subjects.

PURPOSE: Hypertension and dyslipidemia are major risk factors for cardiovascular diseases, and reduction of cardiovascular risks can be achieved by combining antihypertensive therapy with statins. The objective of this study was to evaluate the pharmacokinetic interaction between telmisartan/amlodipine fixed dose combination and rosuvastatin in healthy Korean male volunteers. PATIENTS AND METHODS: An open-label, two-cohort, multiple-dose, single-sequence crossover study was conducted in healthy male subjects. In Cohort 1, the subjects were administered one tablet of telmisartan/amlodipine 80 mg/5 mg once daily for 14 days with or without one tablet of rosuvastatin 20 mg once daily. In Cohort 2, the subjects were administered one tablet of rosuvastatin 20 mg once daily for 14 days with or without one tablet of telmisartan/amlodipine 80 mg/5 mg once daily. Serial blood samples were collected up to 24 hrs post-dose on the 9th and 14th days in Cohort 1 and on the 5th and 14th days in Cohort 2. Plasma drug concentrations were measured by liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters, including maximum plasma concentration at steady state (Cmax,ss) and area under the plasma concentration versus time curve over dosing interval (AUCτ,ss), were determined by non-compartmental analysis. The geometric least-square mean (GLSM) ratios and associated 90% confidence intervals (CIs) of log-transformed Cmax,ss and AUCτ,ss for separate or concurrent therapy were calculated to evaluate pharmacokinetic interactions. RESULTS: Thirty-eight subjects from Cohort 1 and nineteen subjects from Cohort 2 completed the study. The GLSM ratios and 90% CIs of Cmax,ss and AUCτ,ss, were 0.9829 (0.8334-1.1590) and 1.0003 (0.9342-1.0710) for telmisartan; 0.9908 (0.9602-1.0223) and 1.0081 (0.9758-1.0413) for amlodipine; and 2.2762 (2.0113-2.5758) and 1.3261 (1.2385-1.4198) for rosuvastatin, respectively. CONCLUSION: The pharmacokinetic parameters of telmisartan/amlodipine, but not rosuvastatin, met the pharmacokinetic equivalent criteria. The increase in systemic exposure to rosuvastatin caused by telmisartan/amlodipine co-administration would not be clinically significant in practice. Nevertheless, an appropriately designed two-sequence crossover study is needed to confirm the results of this study.