The effectiveness of any medical therapy is determined not only by the therapeutic agent's pharmacokinetic and pharmacodynamic activity, but also, to a significant part, by its bioavailability at the site of action in the human system. Orally administered nano/micro drug systems (Novel Drug Delivery Systems: NDDs) exhibit their higher effectiveness in colon therapy, particularly for bowel diseases such as Crohn's disease, ulcerative colitis, colon cancer. By augmenting drug bioavailability through the protection of the drugs molecules from the acidic area and increasing penetration into the intestinal membrane.

The aim of the present work was to prepare and characterize mesalazine (5-aminosalicylic acid) loaded microspheres consisting of different ratios of sodium alginates (ALG) and ethylcellulose (EC) using emulsion solvent evaporation method for intestinal release.

Properties of the microspheres such as surface morphology and size, FT-IR, DSC, TGA, drug content, drug release behavior, percentage drug entrapment, percentage yield of in vitro drug release were evaluated to investigate the more suitable preparation parameters. Drug release studies were carried out in acidic medium (pH=1.2) for 2h and in phosphate buffer solution (pH=6.8) up to 8h. Ideal slow release of (5-ASA) was highly affected by this coating. Mesalazine had low dissolution ratio in acidic gastric conditions and microspheres exhibited less than 20% of active ingredient release in gastric solution, while more than 50% was released over 7 h in the intestinal conditions medium. The results showed that the sustained release systems thus prepared are suitable for vectorized delivery of the drug if they are administered for colon therapy.