Notes On Drugs: Antacids, Antihistamines And Neurologically Active - CBSE Class 12 Chemistry

Antacids:

Antacids are commonly taken to relieve heartburn, which is a common symptom of gastritis or acidity. The stomach produces gastric acid to aid digestion. This acid is mainly composed of hydrochloric acid. Excessive secretion of the acid can lead to stomach disorders such as gastritis, gastric ulcers and peptic acid disease. These disorders can be treated by antacids, which reduce the amount of acid in the stomach. Antacids contain weak bases that neutralize the acid in the stomach by reacting with them chemically to produce salt and water.

Ex: Sodium hydrogen carbonate reacts with hydrochloric acid to give sodium chloride and water. 

However, antacids provide only temporary relief as they act on the symptoms alone and not on the cause of gastritis. Hence, their effect can wear off quickly and they have to be taken continually to obtain relief.

Antihistamines:

The body's immune system consists of mast cells, which have antibodies attached to them. When antigens come into contact with the antibodies, the mast cells get stimulated and they release chemicals known as histamines and heparins into their surroundings, causing inflammation and irritation.

In case of gastritis, the histamines bind to the receptors in the stomach wall and promote acidity.

In case of allergies such as the common cold, the histamines bind to the receptors in the nasal cavity and cause blood vessels to swell and secrete excess fluid, causing sneezing and a running nose. Antihistamine drugs provide relief from the allergic effects of histamines by attaching themselves to the receptors and thus preventing histamines from binding to receptors. Thus, the histamines are prevented from causing chemical reactions and producing allergic symptoms.

Ex:

Neurologically active drugs affect the message transfer mechanism between nerves and receptors.

Neurologically active drugs are commonly classified as tranquilisers and analgesics.

A tranquiliser is a drug that acts on the central nervous system and is used to calm, lessen hypertension, subside depression (or) put a person to sleep. Tranquilisers ought to be taken in prescribed doses for short periods of time to avoid causing dependence and tolerance.

There are two types of tranquilisers: Major tranquilisers and Minor tranquilisers.

Major tranquilisers are commonly called anti-psychotic drugs, while minor tranquilisers are considered anti-anxiety drugs. Anti-psychotic drugs are used to treat patients with severe mental illnesses such as schizophrenia.

Ex: Haldol, Thorazine and Prolixin.

Anti-anxiety drugs are commonly used to treat emotional problems such as anxiety, depression and sleep disorders.

Ex: Valium, Librium and Xanax

Summary

Antacids:

Antacids are commonly taken to relieve heartburn, which is a common symptom of gastritis or acidity. The stomach produces gastric acid to aid digestion. This acid is mainly composed of hydrochloric acid. Excessive secretion of the acid can lead to stomach disorders such as gastritis, gastric ulcers and peptic acid disease. These disorders can be treated by antacids, which reduce the amount of acid in the stomach. Antacids contain weak bases that neutralize the acid in the stomach by reacting with them chemically to produce salt and water.

Ex: Sodium hydrogen carbonate reacts with hydrochloric acid to give sodium chloride and water. 

However, antacids provide only temporary relief as they act on the symptoms alone and not on the cause of gastritis. Hence, their effect can wear off quickly and they have to be taken continually to obtain relief.

Antihistamines:

The body's immune system consists of mast cells, which have antibodies attached to them. When antigens come into contact with the antibodies, the mast cells get stimulated and they release chemicals known as histamines and heparins into their surroundings, causing inflammation and irritation.

In case of gastritis, the histamines bind to the receptors in the stomach wall and promote acidity.

In case of allergies such as the common cold, the histamines bind to the receptors in the nasal cavity and cause blood vessels to swell and secrete excess fluid, causing sneezing and a running nose. Antihistamine drugs provide relief from the allergic effects of histamines by attaching themselves to the receptors and thus preventing histamines from binding to receptors. Thus, the histamines are prevented from causing chemical reactions and producing allergic symptoms.

Ex:

Neurologically active drugs affect the message transfer mechanism between nerves and receptors.

Neurologically active drugs are commonly classified as tranquilisers and analgesics.

A tranquiliser is a drug that acts on the central nervous system and is used to calm, lessen hypertension, subside depression (or) put a person to sleep. Tranquilisers ought to be taken in prescribed doses for short periods of time to avoid causing dependence and tolerance.

There are two types of tranquilisers: Major tranquilisers and Minor tranquilisers.

Major tranquilisers are commonly called anti-psychotic drugs, while minor tranquilisers are considered anti-anxiety drugs. Anti-psychotic drugs are used to treat patients with severe mental illnesses such as schizophrenia.

Ex: Haldol, Thorazine and Prolixin.

Anti-anxiety drugs are commonly used to treat emotional problems such as anxiety, depression and sleep disorders.

Ex: Valium, Librium and Xanax

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