Oral drug administration is the most commonly used route due to many advantages that can be driven from it which are higher patient compliance, lower pain, ease of administration and decrease levels of infection(1).1.Colon targetingDelivering drugs to their site of action leads to lower side effects and to increase pharmacological action. Colon becomes one of the most interesting areas to be targeted through oral route)(2). Colon related diseases such as Crohn’s disease, ulcerative colitis, inflammatory bowel disease, colorectal cancer, and many others have taken a huge interest in their treatment that can be achieved by colon targeting.
Colon-targeted drug delivery systems provide potential advantages like delivery of high local drug concentration at the impaired part of the colon to produce optimum therapeutic action and reduction in systemic adverse effects associated with the premature release and subsequent absorption of drugs from the upper gastrointestinal tract this differentiates it from the classical oral dosage forms(3). 1.1 Systems developed for colon-specific drug deliverycovalent linkage of a drug with a carrier, time-dependent release systems, coating with pH-sensitive polymers and enzymatically controlled delivery systems which is also called a (microbially triggered system) are Various systems that have been developed for colon-specific drug delivery(2).
Each system of these systems has its own drawbacks, pH-sensitive systems may lose site specificity of drug release because of similar pH values of small intestinal and colonic fluids, time-dependent system has difficulty for accurate prediction of site for drug release because of wide variation in gastric retention time also Microbially triggered systems are affected by factors that may change the composition of the human gut ecosystem and a larger amount of coat is required to prevent premature drug release due to higher hydrophilicity of the polysaccharides(3). The union of two or more systems has shown great results regarding colon-specific drug release leading to minimal drug release in the stomach and small intestine and huge amount of drug released in the colon(4).1.2. Compression coatingFilm coating or compression coating processes are the processes that have been used for colon drug delivery system. Compression coating is a solvent-free process which is safe and inexpensive and it has higher stability when compared to film coating, but it undergoes disadvantages like the requirement of highly skilled persons, and it needs more care during compression to avoid compression-related problems(5).Compression -coated tablets as colonic release systems are usually obtained by coating the drug cores by compression-coating. The coating polymers are classified into soluble or insoluble matrix-forming polymers, capable of controlling drug release by either matrix dissolution or erosion. Examples for these polymers are polysaccharides which control drug release through their enzymatic degradation by the colonic microflora or enteric polymers, which are insoluble in acidic media but dissolve in slightly acid to neutral pH environments(6). 1.3. Soluble forming polymersHydrophilic polymers are highly used in formulating oral controlled-release tablets(1).1.3.1. Hydroxypropyl methylcellulose and hydroxypropyl celluloseHydroxypropyl methylcellulose and hydroxypropyl cellulose are the most often used polymers In the development and production of hydrophilic matrix tablets, these polymers on the surface of the dosage form hydrates and swells once hydrophilic matrix dosage form reached the gastrointestinal tract forming a protective gel layer from which the drug is gradually and continuously released over time. Considering the solubility interplay between the drug and polymer, the release is diffusion-controlled if the solubility of the incorporated drug is greater than the solubility of the polymeric matrix. In contrast, the release is more erosion-controlled if the solubility of the polymeric matrix is greater than the solubility of the incorporated drug(7). Pectin, chondroitin sulfate, amylase, guar gum, xanthan gum ,and chitosan are examples of polysaccharides that are being examined as carriers for colon-specific drug delivery(3). 1.3.2. PolysaccharidesThere are large amounts of polysaccharides that are present in the human colon as the colon is inhabited by a numerous bacteria which secrete many enzymes e.g amylase, pectinase, xylanase, etc(8). Major approaches utilizing polysaccharides for colon-specific delivery are a fermentable coating of the drug core, embedding of the drug in the biodegradable matrix and formulation of drug saccharine conjugate(1).1.4. KetoprofenKetoprofen belongs to nonsteroidal anti-inflammatory drug it is used as an analgesic and anti-inflammatory drug for the treatment of pain and rheumatic diseases. Ketoprofen is considered a good candidate for colon delivery due to the well known gastric side effect. Therefore, there are several research works that studied the strategies of oral administration and colon-specific release of ketoprofen(6).