European Journal of Biomedical and Pharmaceutical Sciences

PREPARATION AND EVALUATION OF CHEWABLE TABLETS OF NAFTOPIDIL

Heba I. Elagamy*, Ahmed T. Nouh, Ebtessam A. Essa and Gamal M. El Maghraby

ABSTRACT

Naftopidil is a weak basic antihypertensive agent and is promising in treatment of benign prostatic hyperplasia. Unfortunately, it has low oral bioavailability due to poor dissolution and extensive pre-systemic metabolism. Accordingly, the objective of this work was to develop chewable tablets which liberate most of naftopidil in the oral cavity. This required dissolution enhancement which was achieved via co-grinding with citric and/or tartaric acid. The co-ground mixtures were evaluated using Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. Optimum mixtures were prepared chewable tablets. Co-grinding of naftopidil with tartaric acid developed amorphous naftopidil. Co-grinding with citric acid alone or in combination with tartaric acid developed co-crystalline product. These physical changes were associated with significant enhancement in naftopidil dissolution rate, even at pH6.8. Incorporation of the co-ground mixtures in SMEDDS was synergistic. The tablets liberated significant amounts of naftopidil at pH 6.8 after crushing. Repeating the dissolution on intact tablets, the results were the same for dry tablets, with liquisolid tablet liberating smaller amount of drug. In conclusion, dry co-grinding of naftopidil with citric and/or tartaric acid modified the crystalline structure with subsequent dissolution enhancement irrespective to the pH. The developed new co-crystalline product was successfully prepared as chewable tablets which underwent pH independent liberation of naftopidil from chewable tablets.

Keywords: Co-grinding, Co-crystal, amorphous solid, dissolution rate, naftopidil, citric acid.