Fixed-dose combination orally disintegrating tablets to treat cardiovascular disease: formulation, in vitro characterization and physiologically based pharmacokinetic modeling to assess bioavailability

Abstract

Cardiovascular disease (CVD) is the leading cause of death among men and women worldwide. In CVD, hypertension and dyslipidemia commonly coexist and are managed through coadministration of amlodipine and atorvastatin, respectively. The case for fixed-dose combination (FDC) oral dosage forms and orally disintegrating tablet (ODT) technology to enhance outcomes and compliance is strong. This work follows the development and characterization of single and FDC ODTs containing amlodipine and atorvastatin, followed by bioequivalence comparison between these single and FDC formulations, using in vitro dissolution and Caco-2 apparent permeability (P_app) and in silico physiologically based pharmacokinetic modeling approaches. ODTs containing amlodipine (5 mg) and atorvastatin (10 mg) either alone or in combination rapidly disintegrated (<30 s) while displaying a radial crushing strength in excess of 100 N and friability ≤1%. In vitro dissolution test was performed in fasted and fed-state simulated intestinal fluid (FeSSIF) and analyzed using high-performance liquid chromatography. Dissolution profiles for single and FDC ODTs were compared using US FDA recommended difference (f₁) and similarity (f₂) factor testing for bioequivalence. In all cases, there was no difference in active pharmaceutical ingredient dissolution between single or FDC ODTs, with the exception of amlodipine in FeSSIF. Pharmacokinetic clinical trial simulations were conducted using Simcyp (Version 14), incorporating P_app and dissolution data. Simulated clinical trials in healthy volunteers showed no difference in bioavailability based on pharmacokinetic parameters between single and combination doses with either active pharmaceutical ingredient. An increase in C_max and AUC for atorvastatin in fed subjects was attributed to extended transit along the gut lumen and reduced atorvastatin metabolism due to lower CYP3A4 expression at more distal small intestine absorption sites. The results demonstrated bioequivalence of an FDC ODT for amlodipine and atorvastatin, while highlighting several limitations of f₁ and f₂ bioequivalence testing and strengths of mechanistic pharmacokinetic modeling for oral drug absorption.

Keywords: bioavailability; bioequivalence; cardiovascular disease; fixed-dose combination; orally disintegrating tablet; physiologically based pharmacokinetic modeling.

Figure 1

Amlodipine (5 mg) dissolution profiles of single and FDC formulations in fasted-state biorelevant media (900 mL, 37°C) from 500 mg ODTs. Dissolution performed using USP 2 paddle apparatus (mean ± SD, n=3). Abbreviations: FDC, fixed-dose combination; ODTs, orally disintegrating tablets; SD, standard deviation; FaSSIF, fasted-state simulated intestinal fluid; USP, United States Pharmacopeia.

Figure 2

Amlodipine (5 mg) dissolution profiles of single and FDC formulations in fed-state biorelevant media (900 mL, 37°C) from 500 mg ODTs. Dissolution performed using USP 2 paddle apparatus (mean ± SD, n=3). Abbreviations: FDC, fixed-dose combination; ODTs, orally disintegrating tablets; SD, standard deviation; FeSSIF, fed-state simulated intestinal fluid.

Figure 3

Atorvastatin (10 mg) dissolution profiles of single and FDC formulations in fasted-state biorelevant media (900 mL, 37°C) from 500 mg ODTs. Dissolution performed using USP 2 paddle apparatus (mean ± SD, n=3). Abbreviations: FDC, fixed-dose combination; ODTs, orally disintegrating tablets; SD, standard deviation; FaSSIF, fasted-state simulated intestinal fluid.

Figure 4

Atorvastatin (10 mg) dissolution profiles of single and FDC formulations in fed-state biorelevant media (900 mL, 37°C) from 500 mg ODTs. Dissolution performed using USP 2 paddle apparatus (mean ± SD, n=3). Abbreviations: FDC, fixed-dose combination; ODTs, orally disintegrating tablets; SD, standard deviation; FeSSIF, fed-state simulated intestinal fluid.

Figure 5

TEER values for Caco-2 monolayers grown on 12 mm Transwell inserts from days 0 to 21 post-seeding. Cells were seeded at a density of 8×10⁴ cells/cm² and maintained in DMEM at 37°C and 5% CO₂ (mean ± SD, n=6). Abbreviations: TEER, transepithelial electrical resistance; DMEM, Dulbecco’s Modified Eagle’s Medium; SD, standard deviation.

Figure 6

Cumulative mass transfer of amlodipine alone (20 μg/mL) across Caco-2 monolayers (pH 7.4) simulating f₁. P_app values were calculated using the gradient of the linear portion of the curve (mean ± SD, n=3). Abbreviation: SD, standard deviation.

Figure 7

Cumulative mass transfer of atorvastatin alone (40 μg/mL) across Caco-2 monolayers (pH 7.4) simulating f₂. P_app values were calculated using the gradient of the linear portion of the curve (mean ± SD, n=3). Abbreviation: SD, standard deviation.

Figure 8

Cumulative mass transfer of amlodipine (20 μg/mL) while in combination with atorvastatin across Caco-2 monolayers (pH 7.4) simulating f₃. P_app values were calculated using the gradient of the linear portion of the curve (mean ± SD, n=3). Abbreviation: SD, standard deviation.

Figure 9

Cumulative mass transfer of atorvastatin (40 μg/mL) while in combination with amlodipine across Caco-2 monolayers (pH 7.4) simulating f₃. P_app values were calculated using the gradient of the linear portion of the curve (mean ± SD, n=3). Abbreviation: SD, standard deviation.

Figure 10

Simulated mean plasma profile after a (A) 80 mg and (B) 10 mg oral dose of atorvastatin (solid black line). The corresponding observed data points are shown by red open circles. The gray lines represent the 5th and 95th percentiles for the predicted values. All simulations were performed using the minimal PBPK model. Abbreviation: PBPK, physiologically based pharmacokinetic.

Figure 11

Simulated mean plasma profile after a 10 mg oral dose of amlodipine (solid black line). The corresponding observed data points are shown by red (set 3) or green (set 4) open circles. The gray lines represent the 5th and 95th percentiles for the predicted values. All simulations were performed using the minimal PBPK model. Abbreviation: PBPK, physiologically based pharmacokinetic.

Figure 12

Simulated mean plasma profile after a 5 mg oral dose of amlodipine (A and B) and 10 mg oral dose of atorvastatin (C and D) under fasted and fed conditions. Single API formulations are indicated in black and fixed-dose combination in red. Solid lines represent trial mean, and dashed lines represent the 5th and 95th percentiles for the predicted values. All simulations were performed using the minimal PBPK model. Abbreviations: API, active pharmaceutical ingredient; PBPK, physiologically based pharmacokinetic.

Figure 13

(A) Mean cumulative fraction dose absorbed; (B) mean solid drug mass in the stomach (left panel) and mean dissolved stomach drug concentration (right panel); (C) duodenal dissolution rate (upper left panel), duodenal luminal concentration (upper right panel), duodenal absorption rate (lower left panel), and duodenal enterocyte concentration (lower right panel). Black solid line represents fasted (single/combined), red solid line represents fed (single), and red dashed line represents fed (combined) formulations.

Figure 13

(A) Mean cumulative fraction dose absorbed; (B) mean solid drug mass in the stomach (left panel) and mean dissolved stomach drug concentration (right panel); (C) duodenal dissolution rate (upper left panel), duodenal luminal concentration (upper right panel), duodenal absorption rate (lower left panel), and duodenal enterocyte concentration (lower right panel). Black solid line represents fasted (single/combined), red solid line represents fed (single), and red dashed line represents fed (combined) formulations.

Figure 14

Ab oral regional distribution of (A) median fraction dose absorbed and (B) median fraction dose metabolized for atorvastatin.