Enteric formulations/coating agents

Hypromellose phthalate is widely used, primarily as an enteric coating agent, in oral pharmaceutical formulations. Chronic and acute animal feeding studies on several different species have shown no evidence of teratogenicity or toxicity associated with hypromellose phthalate.Hypromellose phthalate is generally regarded as a nonirritant and nontoxic material. 

Zein is used as a tablet binder in wet-granulation processes or as a tablet-coating agent mainly as a replacement for shellac. It is used primarily as an enteric-coating agent or in extended-release oral tablet formulations. Zein is also used in food applications as a coating agent. See Table I. 

Buffering agents that are compounded with didanosine to counteract its degradation by gastric acid may interfere with the absorption of other drugs that require acidity (e.g., indinavir, delavirdine, ketoconazole, fluoroquinolones, tetracyclines, dapsone). An enteric-coated formulation Videx EC) that dissolves in the basic pH of the small intestine is not susceptible to these interactions. Ganciclovir and valganciclovir can increase blood levels of didanosine. The use of zalcitabine with didanosine is not recommended because that combination carries an additive risk of peripheral neuropathy. The combination of didanosine with stavudine increases the risk of pancreatitis, hepatotoxicity, and peripheral neuropa-... 

Amines containing APIs have also been known to react with other formulation components such as flavoring agents and even enteric coating constituents. An example of the reaction of a primary amine with a flavoring agent is illustrated in Figure 48 (83). In this example, the API was formulated in a ready-to-use liquid, oil-based formulation, and vanillin was one of the... 

Based on several randomized trials, aspirin has become the preferred antiplatelet agent in the treatment of aU ACSs. Early aspirin administration to all patients without contraindications within the first 24 hours of hospital admission is a quality care indicator (see Table 16-3). The antiplatelet effects of aspirin are mediated by inhibiting the synthesis of thromboxane A2 through an irreversible inhibition of platelet cyclooxygenase-1. Following the administration of a non-enteric-coated formulation, aspirin rapidly (<10 minutes) inhibits thromboxane A2 production in the platelets. Aspirin also has anti-inflammatory actions, which decrease C-reactive protein and also may contribute to its effectiveness in ACS. In patients undergoing PCI, aspirin prevents acute thrombotic occlusion during the procedure. 

A satisfactory formulation of the enteric coating is shown in table 4. In this formulation, stearic acid, hydrogenated castor oil and castor oil constitute the enteric coating base of proper consistency, and the cholesterol and sodium taurocholate are the emulsifying and timing agents. 

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