Gastric mucosa irritant

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. 

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

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. 

Ipecac syrup is prepared from the dried rhizome and roots of Cephaelis ipecacuanha or Cephaelis acuminata, plants from Brazil and Central America that have the alkaloid emetine as their active principal ingredient. It acts directly on the CTZ and also indirectly by irritating the gastric mucosa. Ipecac is cardiotoxic if absorbed and can cause cardiac conduction disturbances, atrial fibrillation, or fatal myocarditis. If emesis does not occur, gastric lavage using a nasogastric tube must be performed. 

Mechanism of Action An antidote that acts centrally by stimulating medullary chemoreceptor trigger zone and locally by irritating gastric mucosa. Therapeutic Effect Produces emesis. 

In clinical practice, Yuan Zhi should be used with caution, because too high a dose can irritate the gastric mucosa, cause nausea and increase the secretion of the respiratory tract. 

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. 

Alcohol consumption causes peripheral vasodilatation the person feels warm, body heat is slowly lost, and an overdose can cause rapid hypothermia. An acute dose of 3 to 4 units will increase blood pressure. It will cause irritation to gastric mucosae followed by erosion that heals after 3 to 4 weeks. At least 60% of chronic gastritis is reported with chronic alcoholics. Alcohol intake also affects sexual function. William Shakespeare wrote that alcohol provides the desire but takes away the performance. Alcohol can be source of energy but cannot be used as food. 

Gastric discomfort Epigastric distress commonly results from irritation of the gastric mucosa (Figure 31.4) and is often responsible for non-compliance in patients treated with these drugs. The discomfort can be controlled if the drug is taken with foods other than dairy products. 

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. 

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