Stomach drug dissolution

For oral delivery, complexes will also dissociate rapidly on dilution in the stomach and intestinal contents and it is generally believed that only the drug, and not the complex, is absorbed (Thompson, 1997). Therefore, the primary function of complexes is to increase the dissolution rate and extent of drug dissolution. Other reported effects of CDs on oral absorption of drugs include enhancement of mucosal membrane permeation by CD as mentioned earlier in this chapter. 

Tablets require a certain amount of strength, or hardness and resistance to friability, to withstand mechanical shocks of handling in manufacture, packaging, and shipping. Adequate tablet hardness and resistance to powdering and friability are necessary requisites for consumer acceptance while immediate-release tablets should readily disintegrate in the stomach as quick possible. For this reason, the relationship of harness to tablet disintegration and drug dissolution has been described.

DIPYRIDAMOLE ANTACIDS Possible l bioavailability of dipyridamole Dipyridamole tablets require an acidic environment for adequate dissolution t in pH of the stomach impairs dissolution and therefore may 1 absorption of the drug t the dose of dipyridamole or consider using an alternative antiplatelet drug... 

In order for a drug to be absorbed, it must be dissolved in the fluid at the absorption site. A drug administered orally in a tablet or capsule dosage form cannot be absorbed until the drug particles are solubilized by the fluids at some point within the GI tract. When the solubility is dependent upon either an acidic or basic medium, the drug would be solubilized in the stomach or intestines, respectively. Drug dissolution is described by the Noyes-Whitney Equation ... 

The effective disintegration, dissolution and eventual absorption of dipyridamole in tablet form depends upon having a low pH in the stomach. Drugs that raise the gastric pH significantly are expected to reduce the bioavailability of dipyridamole. 

The rationale of the dosage form design (e.g., if a drug is rapidly destroyed in solution at a pH of 2 or below, the design of an oral product must enable the drug to get through the stomach without substantial dissolution)... 

A drug should always be ingested with a cup of water ( 8 oz) to insure easy transit down the esophagus and to provide fluid for disintegration and dissolution. Whether or not the drug should be taken on an empty stomach (e.g., enteric-coated tablets) or with food will depend upon the specific drug as noted above. 

In addition to these in vitro demonstrations of the importance of the effective surface area of drug particles on dissolution rate, many in vivo studies are available. Phenacetin plasma levels versus time are plotted for three different particle sizes of phenacetin in Fig. 14. Healthy adult volunteers received 1.5-g doses of phenacetin as an aqueous suspension on an empty stomach. The results show that both the rate and... 

Usually, an increase in Cg that would affect the dissolution rate would occur only when another process, such as membrane transport or stomach emptying, becomes the rate-limiting step in drug absorption. As a general rule pharmacists should advise patients to take their oral medications with a full glass of water to ensure that dissolution occurs under optimal conditions. 

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