Prolonged Intragastric Drug Delivery Mediated by Eudragit®E-Carrageenan Polyelectrolyte Matrix Tablets

Interpolyelectrolyte (IPE) complexation between carrageenan (CG) and Eudragit E (EE) was studied in 0.1 M HCl and was used to develop floating matrix tablets aimed to prolong gastric-residence time and sustain delivery of the loaded drug. The optimum EE/CG IPE complexation weight ratio (0.6) was determined in 0.1 M HCl using apparent viscosity measurements. The IPE complex was characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Metronidazole matrix tablets were prepared by direct compression using EE, CG, or hybrid EE/CG with ratio optimal for IPE complexation. Corresponding effervescent tablets were prepared by including Na bicarbonate as an effervescent agent. Tablets were evaluated for in vitro buoyancy and drug release in 0.1 M HCl. Both CG and EE–CG effervescent matrices (1:2 drug to polymer weight ratio, 60 mg Na bicarbonate) achieved fast and prolonged floating with floating lag times less than 30 s and floating duration of more than 10 h. The corresponding EE effervescent matrices showed delayed floating and rapid drug release, and completely dissolved after 3 h of dissolution. CG matrices showed an initial burst drug release (48.3 ± 5.0% at 1 h) followed by slow drug release over 8 h. EE–CG matrices exhibited sustained drug release in almost zero-order manner for 10 h (68.2 ± 6.6%). The dissolution data of these matrices were fitted to different dissolution models. It was found that drug release followed zero-order kinetics and was controlled by the superposition of the diffusion and erosion

Influence of Formulation Factors on Tablet Formulations with Liquid Permeation Enhancer Using Factorial Design

For a drug with low bioavailability, a matrix tablet with liquid permeation enhancer (Labrasol®) was formulated. Factorial design was used to evaluate the effect of three formulation factors: drug percentage, polymer type (Methocel® K100M or Eudragit® L 100-55), and tablet binder percentage (Plasdone® S-630) on tablet characteristics. Tablets were prepared by direct compression and characterized. Compressibility index values ranged between 15.90% and 29.87% and tablet hardness values from 7.8 to 29.78 Kp. Eudragit®-containing formulations had better compressibility index values with higher tablet hardness. Time for 75% of drug release (T75) was calculated, and formulations containing Eudragit® L 100-55 had faster release rates than tablet formulations with Methocel® K100M. Formulations with Methocel® K100M fit well in the Higuchi model as indicated by their R2 values (>0.98). Among all the formulation factors studied, polymer type displayed the highest and statistically significant effect on compressibility index, tablet hardness, and dissolution rate. Statistical design helped in better understanding the effect of formulation factors on tablet characteristics important for designing formulations with desired characteristics