ABSTRACT:
Floating matrix tablets of cefixime trihydrate were developed to prolong gastric residence time and increase drug absorption further increasing the bioavailability. Cefixime trihydrate was chosen as a model drug because it is well absorbed from stomach and upper part of small intestine. A simple Spectrophotometric method has been employed for the estimation of cefixime. This method is based on the formation of yellow to yellowish brown complex of cefixime with palladium (II) chloride in the presence of sodium lauryl sulphate. The tablets were prepared by direct compression technique, using polymer such as hydroxy propyl methyl cellulose (HPMC K4M), sodium CMC and carbopol 934P in different combinations with other standard excipients like sodium bicarbonate and lactose. Sodium bicarbonate used as gas generating agent and lactose was used as filler. Magnesium stearate used as lubricant. Tablets were evaluated for physical characterization viz. hardness, friability, swelling index, floating capacity, thickness and weight variation. Further tablets were evaluated for in-vitro drug release up to 12 hr. The effect of polymer concentrations on buoyancy and drug release pattern was also studied. In-vitro drug release mechanism was evaluated by PCP V-3 software. Carbopol 934P had a negative effect on the floating properties also decreased the drug release. But Carbopol provided a firm structure to the swollen tablet. A lesser Floating lag time (FLT) and a prolonged floating duration could be achieved by varying the amount of effervescent and using different polymer concentrations. All the matrix tablets showed significantly greater swelling index due to the swelling agents like sodium CMC. The sodium CMC containing formulations had greater swelling index compared to other. Polymer swelling is crucial in determining the drug release rate and is also important for floatation. All the tablets exhibited controlled and prolonged drug release profiles and some floated over the dissolution medium for more than 12 hr. The type of polymer affects the drug release rate and the mechanism. The paddle speed affected the floating lag time and floating duration it had a negative effect on the floating properties. The optimized formulation followed the higuchi release model and showed non-fickian diffusion mechanism. It also showed no significant change in physical appearance, drug content, floatability or in-vitro drug release pattern after storage at 45o C at 75 % RH for three months.