Tablet formulated with coatings

Like many other herbal extracts, valerian extract is very hygroscopic. Inclusion into tablets raises stability issues. Coatings reduce moisture absorption but often lead to tablet explosion or visual deterioration (black specs). Tablets formulated with 250 mg valerian extract, spray-dried lactose, and compressible starch were... 

Tablets may be formulated with coatings such as shellac, resin, or styrene-maleic acid copolymer. These coatings are insoluble in acid but dissolve readily at neutral or alkaline pH. Thus they are ideally suited to prevent drug release until the formulation has passed from the stomach into the small intestine. Preventing drug release in the stomach may protect drugs that are acid labile. It may also protect the patient from irritant substances like iron salts, diethylstilbo-estrol, and some anti-inflammatory agents. Release, and subsequent systemic availability of drugs from these formulations is likely to be highly sensitive to stomach emptying patterns.

The stereoselective release behaviors of low-swelling molecularly imprinted polymer bead matrices in pressed-coat tablets were studied using either R- or S-propranolol selective MIPs. The in vitro release profiles of the low-swelling matrices showed a difference in the release of enantiomers, in that the nontemplate isomer was released faster than the template isomer. However, in the last phase of dissolution this difference was reduced and later reversed [64]. Stereoselectivity of release profiles for propranolol enantiomers were identified in MIP synthetic membranes from tablet formulations with significant differences between enantiomers [65]. Release of the enantiomer used as the print was always faster than the... 

As previously discussed, food effects are an important parameter for enteric-coated systems, especially for drugs, that are sensitive to food. Pancreatic enzyme-containing products fail when they come in contact too early with lipids, proteins, and carbohydrates present in food. The clinical efficacy of pancreatic enzymes formulated as enteric-coated tablets was investigated in man and dog [44], The enteric materials examined were hydroxypropyl methylcellulose phthal-ate (HPMCP), cellulose acetate phthalate (CAP), and the methacrylic acid copolymer USP/NF Type C. In vivo behavior monitored by x-ray scintigraphy showed clear differences between the three coating formulations. HPMCP-coated products adhered to the gastric mucosa, whereas CAP and methacrylate copolymer... 

In 1994, due to the successful implementation of both this system and that used to formulate tablets, it was decided to initiate work on a new system that would recommend film-coating formulations for the generated tablet formulations, combined with a reformulation routine based on the film defect diagnosis system. The structure of the new system is shown in Fig. 11. The knowledge for the system was acquired by interviewing two domain experts, one with extensive heuristic knowledge and the other with extensive research knowledge. The sequence is as follows unital)... 

The main use of ethylcellulose in oral formulations is as a hydrophobic coating agent for tablets and granules. Ethylcellulose coatings are used to modify the release of a drug, to mask an unpleasant taste, or to improve the stability of a formulation for example, where granules are coated with ethylcellulose to inhibit oxidation. Modified-release tablet formulations mav also be produced using ethylcellulose as a matrix former. " ... 

Hypromellose phthalate may be used alone or in combination with other soluble or insoluble binders in the preparation of granules with sustained drug-release properties the release rate is pH-dependent. Since hypromellose phthalate is tasteless and insoluble in saliva, it can also be used as a coating to mask the unpleasant taste of some tablet formulations. Hypromellose phthalate has also been co-precipitated with a poorly soluble drug to improve dissolution characteristics. 

Granulates of xylitol are used as diluents in tablet formulations, where they can provide chewable tablets with a desirable sweet taste and cooling sensation, without the chalky texture experienced with some other tablet diluents. Xylitol solutions are employed in tablet-coating applications at concentrations in excess of 65% w/w. Xylitol coatings are stable and provide a sweet-tasting and durable hard coating. 

The nature of tablet or capsule coating -evidence that coating may interfere with the disintegration or dissolution of the formulation... 

Because the mechanism of action of sulfasalazine is not related to the sulfapyridine component, and since sulfapyridine is believed to be responsible for many of the adverse reactions to sulfasalazine, mesalamine alone can be used. Mesalamine can be used topically as an enema for the treatment of proctitis, or given orally in slow-release formulations that deliver mesalamine to the small intestine and colon (Table 34—5 and Fig. 34-1). Slow-release oral formulations of mesalamine such as Pentasa release mesalamine from the duodenum to the ileum, with about 75% of the drug passing into the colon. Olsalazine is a dimer of two 5-aminosalicylate molecules linked by an azo bond. Mesalamine is released in the colon after colonic bacteria cleave olsalazine. Balsalazide is a mesalamine prodrug that is enzymatically cleaved in the colon to produce mesalamine. The recommended daily doses of the oral mesalamine derivatives are intended to approximate the molar equivalent of mesalamine present in 4 g of sulfasalazine. At present, snlfasalazine is nsed in preference to oral mesalamine derivatives, mainly becanse it costs mnch less. However, it is not tolerated as well as the mesalamine altematives. Becanse the oral mesalamine formulations are coated tablets or grannies, they should not be crushed or chewed. 

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