Floating lag time

This study aimed to develop hydrophilic matrix based controlled release  gastroretentive drug delivery system of Lamivudine floating matrix tablets, which after oral administration are designed to prolong the gastric residence time, increase the drug bioavailability and diminish the side effects of irritating drugs. FTIR studies revealed that there is no interaction between the drug and polymers used for the formulation. Among all the formulations F21 containing HPMC K100M, Carbopol 934P, Polyox WSR 303 and sodium bicarbonate, as gas generating agent was selected as optimized formulation based on physico chemical properties, floating lag time (34 sec) and total floating time (>24 h). From in vitro dissolution studies, the optimized formulation F21 showed drug release of 99.36±5.36%, whereas 92.36±5.02% of the drug was released from the marketed product within 24h. From in vivo bioavailability studies, after oral administration of floating tablet containing 100 mg Lamivudine, the Cmax, Tmax, and AUC0–∞ of optimized gastroretentive formulation were found to be 32.11±3.16 µg/mL, 8.00±1.26 h and 225±28.14 µg*h/ml, respectively. Cmax and AUC values of optimized formulation were found to be significantly higher than of marketed product, where longer gastric residence time is an important condition for prolonged or controlled drug release and also for improved bioavailability. Hence, gastro retention can be a promising approach to enhance bioavaiilability of Lamivudine with narrow absorption window in upper GIT.

Conventional drug therapy requires periodic doses of therapeutic agents. These agents are formulated to produce maximum stability, activity and bioavailability.  Floating drug delivery systems (FDDS) have a bulk density less than gastric fluids and so remain buoyant in the stomach without affecting gastric emptying rate for a prolonged period of time. While the system is floating on the gastric contents drug is released slowly at the desired rate from the system. The present study mainly focuses on the development and evaluation effervescent based floating matrix tablet of famotidine. This oral drug delivery offers several advantages over the standard conventional oral dosage forms. Effervescent based floating matrix tablet of famotidine was prepared using sodium bicarbonate as effervescent agent and by incorporating hydrophobic agent stearic acid which retards the drug release and allow the dosage form to float on gastric fluid for several hrs. Then the tablet was evaluated for hardness, friability, drug content and in vitro drug release. On the basis of the preliminary trials, a 32 full factorial design was employed to study the effect of independent variables, HPMC K4M: Carbopol 934P ratio (X1) and concentration of effervescent agent (X2) on dependent variables like floating lag time, Q4 and Q8. The best batch (F3) exhibited optimum floating lag time (16 sec), drug content (98.94%), Q4 (54.36 %), Q8 (93.98%) and similarity factor (83.92). The controlled release of famotidine was observed and good fit to the zero order was demonstrated.