Comparative Delivery of Diltiazem Hydrochloride Through Synthesized Polymer: Hydrogel and Hydrogel Microspheres Debajyoti Ray, 1 P. Sunny Gils, 2 Guru P. Mohanta, 3 R. Manavalan, 3 Prafulla K. Sahoo 2 1 P.G. Department of Pharmaceutics, Sri Jayadev College of Pharmaceutical Sciences, Bhubaneswar 752101, Orissa, India 2 Polymer Research Unit, Department of Chemistry, Utkal University, Bhubaneswar 751004, Orissa, India 3 Department of Pharmaceutics, Annamalai University, Annamalai nagar 608002, Tamil Nadu, India Received 11 May 2009; accepted 25 October 2009 DOI 10.1002/app.31661 Published online 10 December 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: In this study, interpenetrating polymer net- work (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with polyacrylic acid (PAA) were prepared by a non-conventional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and so- dium chloride (NaCl) as additive. The IPN hydrogel was characterized by using Fourier transformed infrared (FTIR) spectrophotometry, Thermo gravimetric analysis (TGA), and Scanning electron microscopy (SEM). (PVA-co-PAA)/ NaCl normal IPN hydrogel (H) were fabricated into hydrogel microspheres (HM) by modified emulsion cross- linking method using glutaraldehyde-saturated toluene as crosslinker and were loaded with Diltiazem hydrochloride (DL). The IPN hydrogel showed more swelling in simu- lated intestinal fluid (SIF). (PVA-co-PAA)/NaCl HM for- mulation A1 showed comparatively higher DL entrapment (79%) and better control over DL release up to 24 h. By comparing antihypertensive activity of DL loaded two for- mulations in normotensive rats, HM formulation A1 found more effective in reducing blood pressure to 40.1%. The experimental results demonstrated that (PVA-co-PAA)/ NaCl HM had the greater potential than normal hydrogel to be used as a drug carrier. A single use of the prepared hydrogel microsphere system of DL can effectively control hypertension in rats. The system holds promise for clinical studies. V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 959–968, 2010 Key words: normal hydrogel; hydrogel microspheres; drug delivery; swelling studies; stability study INTRODUCTION Polymeric drug carriers of various size have attracted increasing attention in recent years. Now-a-days, it would be most desirable for drug release to match a patient’s physiological needs at the proper time and/or the proper site. This is why there is a great interest in the development of con- trolled delivery systems. 1 Polymeric hydrogels are of considerable interest as biomaterials in drug delivery research. 2–9 The crosslinked hydrogels are gaining importance in a wide variety of applications as superabsorbents in wound dressings, as drug car- riers, as artificial organs, etc. Such systems are highly advantageous over conventional materials because their water uptake properties can be altered by chemically modifying their structures. Hydrogels can respond to external stimuli, such as pH, ionic strength, temperature, and electric current. Such polymeric systems are useful as stimulus responsive drug carriers and are often called ‘intelligent’ or ‘smart’ materials because of their quick response to the external stimuli. The pH-sensitivity of the hydro- gels is due to the presence of weakly acidic and/or basic functional groups on the backbone. Their water uptake properties are attributed to the ionization of functional groups, which depend upon the pH and ionic strength of the external medium thereby mak- ing them useful as pH-sensitive drug delivery sys- tems. Such systems are also called pH-dependent ‘switch-on and -off systems’. 10 From last few years, hydrogel microspheres have shown their efficacy in delivering various drugs to different areas of body. 11–14 By controlling size of the microspheres, the targeted delivery of the drugs to the required area of various organs becomes realizable. Polyvinyl alcohol (PVA) has been used in a wide variety of fields since its discovery in 1924, because of its desir- able properties, such as non toxicity and non carci- nogenicity. 15 PVA 16–19 and Polyacrylic acid (PAA) 20–23 finds extensive biomedical applications including drug delivery to specific areas of body. In our previ- ous work, 23 we have synthesized copolymeric hydro- gel of polyacrylamide, PAA and studied the size dependent delivery of 5-Florouracil to the colon. Correspondence to: P. K. Sahoo (psahoochemuu@satyam. net.in). Journal of Applied Polymer Science, Vol. 116, 959–968 (2010) V C 2009 Wiley Periodicals, Inc.