Colonic enteric coatings

Sulfasalazine Azulfidine Azulfidine Entabs Sulfazine Sulfazine EC Immediate-release or enteric-coated tablets 500 mg 2-6 g Colon... 

By administering both sizes of formulation simultaneously, a better discrimination of relative transit of the two phases can be made. In a cohort of 22 healthy young volunteers, an enteric-coated capsule was administered which contained tablets ("mTc-labeled 5 mm or 8.4 mm diameter) together with pellets (mIn-labeled 0.2 mm ion-exchange resin particles). The unit delivered the radiopharmaceuticals simultaneously to the ileocecal junction [44]. Under control conditions, no difference was observed between the rate of transit through the ascending colon of 0.2-mm particles versus 5-mm tablets, or 0.2-mm particles versus 8.4-mm tablets. The mean period of residence of 50% of the administered 0.2-mm particles in the ascending colon was 11.0 + 4.0 h. 

The solubility should be measured at all of these pH values with a suitable, validated method such as shake-flask or pSol (2) at 37°C to determine whether the (envisaged) dose of the drug can be completely dissolved at all points of interest in the GI tract (see Chapter 11 for more discussion of solubility determination). Typically, this would be the upper GI pH (stomach and proximal small intestine) for immediate release (IR) products, the pH in the small intestine for enteric-coated products and, additionally for MR dosage forms intended to release over a period of six hours or more, the pH in the proximal colon. 

Attempts have been made to achieve colon-speeifie delivery of drugs. These include prodrugs and enteric coated polymers that are sensitive to degradation by bacterial enzymes, and matrices and hydrogels suseeptible to degradation by baeterial enzymes. 

R. Wilding, S. S. Davis, F. Pozzi, P. Furlani, A. Gazzaniga, Enteric coated timed release for colonic targeting, Int J Pharmaceutics 777 99-102 (1994). 

Numerous strategies have been developed to achieve colon-specific drag delivery. Some approaches, such as the use of sustained release formulations, enteric-coated dosage forms and osmotic pumps, were not... 

Davis SS, Hardy JG, Fara JW (1986) Transit of pharmaceutical dosage forms through the small intestine. Gut 27 886-892 Hardy JG, Wilson CG, Wood E (1985) Drug delivery to the proximal colon. J Pharm Pharmacol 37 874-877 Hardy JG, Healy JNC, Lee SW, Reynolds JR (1987) Gastrointestinal transit of an enteric coated delayed release 5-aminosalicylic acid tablet. Aliment Pharmacol Ther 1 209-216... 

CODES A colon-targeted delivery system for proteins/peptides and other drugs. The system contains drug and lactulose as a core formulation, which is subsequently coated first with an enteric coating and then with a cationic polymer coating. Insulin ... 

Wilding, I.R. Davis, S.S. Pozzi, F. Furlani, P. Gazzaniga, A. Enteric coated timed released systems for colonic targeting. Int. J. Pharm. 1994, 111, 99-102. 

The use of oral enteric-coated mesalazine, which releases mesalazine in the terminal ileum and colon, has been reviewed (88,100). Dose-related improvements in clinical and endoscopic parameters have been reported with prolonged-release mesalazine 1-A g/day in trials in patients with mild to moderately active ulcerative colitis. About 74% of patients with mild to moderate ulcerative colitis improve with enteric-coated mesalazine 2.4. 8 g/ day. There is a trend toward a better response with higher doses. Oral enteric-coated mesalazine 0.8-4.4 g/day appears to be as effective as sulfasalazine 2-4 g/day, modified-release mesalazine 1.5 g/day, and balsalazide 3 g/day in maintaining remission in ulcerative colitis. 

Citric acid (as either the monohydrate or anhydrous material) is widely used in pharmaceutical formulations and food products, primarily to adjust the pH of solutions. It has also been used experimentally to adjust the pH of tablet matrices in enteric-coated formulations for colon-specific drug delivery. Citric acid monohydrate is used in the preparation of effervescent granules, while anhydrous citric acid is widely used in the preparation of effervescent tablets.Citric acid has also been... 

Nykaenen P, Sten T, Juerjenson H, Veski P, Marvola M. Citric acid as a pH-regulating additive in granules and the tablet matrix in enteric-coated formulations for colon-specific drug delivery. Pharmazie 2004 59(4) 268-273. 

Nykanen P, Lempaa S, Aaltonen M-L, et al. Citric acid as excipient in multiple-unit enteric-coated tablets for targeting drugs on the colon. Int J Pharm 2001 229(1-2) 155-162. 

Peppermint oil menthol, the principal constituent of peppermint oil, has been shown to have a relaxant action on smooth muscle. The oil acts directly on the colon and is formulated as enteric-coated capsules to prevent dispersal higher up the gastrointestinal canal. It may nevertheless exacerbate heartburn symptoms. 

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