Formulation and Evaluation of a Floating tablet of Amoxicillin and Metronidazole

Abstract

Two ideal rationales of this project are namely, spatial placement and temporal delivery
of a drug. Combination of amoxicillin and metronidazole has higher eradication of H.
pylori. Amoxicillin is a drug having tendency to degrade in alkali, it decompose first by
opening the lactame to its penicilloic acid. Floating tablet would put advantage to release
drug only in acidic medium that would protect amoxicillin to expose in alkali.In this
research first of all a noneffervescent floating drug delivery was used to achieve in vitro
buoyancy. In the initial batches tablets prepared using polymers such as HPMC K100M,
guar gum and xanthan gum did not exhibit sufficient swellin g o provide in vitro
buoyancy. An effervescent approach was then adopted. Three batches (A1 to A3) were
prepared using HPMC K 100M, guar hum, and xanthan gum, respectively; sodium
bicarbonate was added as a gas generating agent. Sodium bicarbonate induced CO2
generation in the presence of dissolution media. The gas generated was trapped and
protected within the gel formed by hydration of polymer, thus decreasing the density of
the tablet. As the density of tablet falls below 1, the tablet becomes buoyant. Batches A2
and A3, containing guar gum and xanthan gum, failed to form a gel with sufficient
strength, entrapping CO2 gas and imparting stable and persistent bouncy.
To study the effect of sodium bicarbonate concentration on floating lag time batches A4 was formulated. The results demonstrate
that as the amount of sodium bicarbonate decreases, the floating lag time increases and total floating time decreases. Thus sodium
bicarbonate (100mg) was essential to achieve optimum in vitro buoyancy. Fed condition and presence of H. Pylori elevate pH of
stomach so citric acid was incorporated in formulation to provide an acidic medium for sodium bicarbonate. However, adding
citric acid to formulation might enhance dissolution, stearic acid was incorporated in the formulations to sustain release.
Decreasing concentration of stearic acid in formulations (A9 to A12), raised drug release profile and decreased total floating time
of tablets. Only one batch, A9, showed sufficient drug release (11 hours) but it could float only for the 10 hours.Finally batch A8
formulated with higher quantity of citric acid compared to A9, which improved total floating time of tablet, from 10 to 11 hours.
Both batches (A8, A9) released drugs in almost same time (11 hours) but floating time was improved in batch A8 compare to A9
due to raised quantity of citric acid.