Formulation design and in vitro evaluations for stomach specific drug delivery system of anti retroviral drug-acyclovir

Floating matrix tablets or stomach specific drug delivery systems are designed to prolong the gastric residence time after oral administration, at a particular site and controlling the release of drug, especially useful for achieving controlled plasma level as well as improving bioavailability. Due to low gastric retention time, the bioavailability of acyclovir is low as the large portion of drug misses the absorption window. The objective of this study was to develop a stomach specific drug delivery system of acyclovir using gas‐forming agent like sodium bicarbonate and polymers like different grades of HPMC and xanthun gum. Tablets were prepared by direct compression using different concentrations of HPMC and xanthun gum. Tablets were evaluated for their physical characteristics, viz., hardness, friability, weight variation and floating properties. The floating lag time of all the formulations was within the prescribed limit (<10 minutes). All the formulations showed good buoyancy and swelling index properties. From in vitro drug release studies, it is concluded that all the formulation retarded the release of drug for twelve hours except AF-1 formulation. AF-8 formulation with 30% xanthun gum shows more controlled release of 60.22% at the end of 12hrs when compared to all other formulations. Key-Words: Acyclovir, HPMC, Xanthun gum, In vitro drug release studies Introduction Various approaches have been proposed to control the gastric residence of drug delivery systems in the upper part of the GIT including floating drug delivery systems (FDDS) [1, 2] high density DDS [3] mucoadhesive systems [4, 5, , swelling and expanding DDS , modified shape systems [8] and other delayed gastric devices . FDDS is a gastroretentive dosage form (GRDF), which can prolong the gastric residence time (GRT) to produce an acceptable drug bioavailability [10, . FDDS or hydrodynamically balanced systems have a bulk density lower than gastric fluid and thus remain buoyant in the stomach without affecting the gastric emptying rate for a prolonged period of time . Acyclovir is a potent antiviral drug with low toxicity used in treatment of herpes simplex infection & varicella zoster infection. It has maximum absorption in the stomach, and half life is 3 hrs. It is widely prescribed for the treatment of Herpes simplex virus infections, as well as in the treatment of Herpes zoster (shingles). Bioavailability of acyclovir is 10– 20% when given orally owing to an important first pass metabolism. * Corresponding Author Email: [email protected] Inorder It has an elimination half-life of 2-3 hours and has an absorption zone from the upper intestinal tract. Due to low gastric retention time, the bioavailability of drug is low as the large portion of drug misses the absorption window. Floating matrix tablets are designed to prolong the gastric residence time after oral administration, at a particular site and controlling the release of drug, especially useful for achieving controlled plasma level as well as improving bioavailability . Material and Methods Materials Acyclovir was obtained as gift sample from Strides Arco, Bangalore. All grades of HPMC and Xanthan gum were obtained from Yarrow Chemicals, Mumbai. Sodium bi carbonate obtained from Fisher scientific, Mumbai. All other chemicals used in the study were of analytical grade. Method Direct compression technique The composition of different formulations of acyclovir floating tablets shown in Table 1. The powder mixture contains drug, controlled release polymers as for the formulae and lactose was used as the diluent, sodium bicarbonate added as effervescent agent. The blend was lubricated with magnesium Research Article [Naveen et al., 4(3): March., 2013] CODEN (USA): IJPLCP ISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 3: March: 2013, 2506-251