Question

Which one of the following is used as antihistamine?
(a) Norethindrone
(b) Chloramphenicol
(c) Diphenhydramine
(d) Omeprazole

Answer 1

Hint: A pharmaceutical drug is a chemical substance, which if administered to a living organism will produce a biological effect. It is used to promote well-being along with treating, curing, preventing, or diagnosing a disease. Antihistamines block histamine release from histamine-1 receptors. They are generally used to treat allergies or cold and flu symptoms, but can also be used for other conditions.

Complete step by step solution:
In order to solve this question, we first need to understand the meaning of pharmaceutical drugs. It is a chemical substance, which if administered to a living organism will produce a biological effect. It is used to promote well-being along with treating, curing, preventing, or diagnosing a disease. Traditionally drugs were prepared through extraction from medicinal plants but now they are also prepared in labs through organic synthesis. Drugs are classified into particular groups based on their similar chemical structures, the mechanism of action (biological target is the same), a related mode of action, and their usage for treating the same disease. The most widely used drug classification system; The Anatomical Therapeutic Chemical Classification System (ATC) assigns drugs a unique ATC code (alphanumeric code) that assigns it to specific drug classes within the ATC system.
Let us look into antihistamines in detail. Antihistamines block histamine release from histamine-1 receptors. They are generally used to treat allergies or cold and flu symptoms, but can also be used for other conditions. Histamine-1 receptors are present in the airways, blood vessels, gastrointestinal tract (oesophagus and stomach), brain and spinal cord. Activation of these receptors can cause conditions such as a skin rash or inflammation, bronchoconstriction, hay fever or motion sickness. Stimulation of Histamine-1 receptors also makes you more awake and alert. Therefore when we take antihistamines we feel drowsy.
Norethindrone is a contraceptive. Chloramphenicol is an antibiotic. Omeprazole is a proton-pump inhibitor.

Hence the correct answer is (c) Diphenhydramine

Note: Initially antihistamines were used in order to prevent stomach-acid related conditions such as irritation of the oesophagus, heartburn and formation of ulcers in the stomach. But now proton pump inhibitors are more widely used in place of antihistamines. They are also used to treat gastroesophageal reflux disease.