Irritants to the gastric mucosa

GI irritation Assessment of potential irritancy to the gastric mucosa Emesis nausea, vomiting... 

Absorption is complete following administration of the oral dosage forms. Peak levels are observed 3-7 hours after oral administration of the capsules. Animal studies indicate that chronic administration of the solution may prove irritating to the gastric mucosa. Ethosuximide is uniformly distributed in total body water, ie, 0.7 L/kg and does not penetrate fat. Ethosuximide is not protein-bound, and spinal fluid concentrations are therefore equal to plasma concentrations. 

Enteric coating materials are also used to prevent release of the drug substance in the stomach if the drug is either an irritant to the gastric mucosa or unstable in gastric juice. Table 7 lists enteric coating polymers commonly used in tablet formulations. The choice of of enteric coating material depends on its solubility. 

It is obvious that drugs such as nifedipine and both isosorbide-5-mononitrate and isosorbide dinitrate, which have non-specific, wide absorption sites and so are well absorbed along the entire GI tract, may not be suitable candidates for GRDDS. Also, drugs that are irritant to the gastric mucosa " and those undergoing significant first-pass metabolism may have some limitations. Relevant examples of the latter type are nifedipine, propranolol, levodopa, diltiazem, metopro-lol and 5-fluorouracil. 

Drugs that are an irritant to the gastric mucosa and cause unpleasant side effects such as nausea and vomiting. Examples include aspirin and other NSAIDS (e.g., naproxen). 

Aspirin is very irritating to the gastric mucosa and should be taken with food to help prevent gastric irritation resulting in ulcers. Enteric-coated aspirin is used to help prevent this complication. 

Carbasalate calcium is irritating to the gastric mucosa. Therefore, it cannot be administered in capsules. It is administered as single-dose powders in sachets instead. The powders should be dissolved in a glass of water before ingestion. When carbasalate calcium powders are prepared in a pharmacy, the poor flow properties of the active substance may result in a relatively low uniformity of mass. The poor flow of the powder is probably due to an irregular shape of the carbasalate calcium crystals and perhaps also to a relatively wide size distribution of the raw material. 

Direct effects include the action of corrosive TIC on the pharynx, oesophagus or stomach. Examples include many household chemicals such as bleach or disinfectants. Many other substances also act as irritants to the gastric mucosa. 

A high rate of ethanol consumption can lead to inhibition of gastric secretion and irritation of the gastric mucosa. Ethanol irritates the entire gastrointestinal tract, which may lead to constipation and diminished absorption of nutrients. Other pathological effects include pancreatitis and peripheral neuropathy. Severe gonadal failure is often found in both men and women, accompanied by low blood levels of sex hormones. 

The toxicity of acute iron poisoning includes local effects on the gastrointestinal mucosa and systemic effects induced by excessive iron in the body. Iron is irritating to the gastric and duodenal mucosa, which may result in hemorrhage and occasional perforations. Once... 

As an emetic, 20-40 mg of emetine for adults, the effect is shown after 20-40 mins, due to local irritation of the gastric mucosa, which produces reflex vomiting and also at a centrally mediated action on the chemore-ceptor trigger zone. 

Administer potassium chloride supplements (Table 10-1) orally (may take 30 minutes for onset) or IV. Use a central IV Mne for rapid infusion in critical conditions. Take with at least a half a glass of fluid (juice or water) because potassium is extremely irritating to the gastric and intestinal mucosa. 

Delivery systems that respond to changes in pH have been known to the pharmaceutical industry for more than a century. The pH-sensitive enteric coating is probably the oldest controUed-release technology. Unna introduced an enteric tablet coating based on keratin in 1884 (108). Enteric coatings are used primarily to protect the gastric mucosa from local irritation or to ensure that tablets do not dissolve until they reach the intestine. 

---