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Classification of Drugs

Drugs and Their Classification-Introduction, Classification, Difference Between Drugs and Medicines, Practice problems, FAQs

You must have seen a difference in the prescription of two unhealthy people which is prescribed by a doctor. Whenever you feel uneasy or fall sick, you should consult your doctor first, then he will prescribe you some medicine based on the symptoms you have. A small kid suffering from fever has been prescribed another medicine and a young man suffering the same is prescribed another. Why this happens, have you ever asked to your doctor. This is due to the classification of drugs based on the nature and symptoms of human activity. Medicines also have a wide range. A lot of chemicals are required to develop a single medicine. Scientists work hard to develop this and are then tested properly before it comes to use. 

Let us study the classification of drugs and their importance.


Table of content:

  • What are drugs?
  • Classification of drugs
  • Difference between drugs and medicines
  • Practice problems
  • Frequently asked questions-FAQ

What are drugs?

Drugs or medicines are chemicals that produce changes in the functional and or mental nature of animals. It is used to diagnose or prevent, cure diseases and to alleviate pain. Drugs are classified in terms of their chemical structure mode of action, physiological effect and mechanism of action

Classification of drugs:

Drugs are man-made chemicals with specific functions. These compounds are specifically formulated and manufactured to treat a variety of disorders and diseases that impact the human body. To locate cures for all types of ailments, a medical student needs to have extensive knowledge of the numerous pharmaceutical medications and their classifications.

Drugs are chemical substances that, when consumed, change the way the body functions, either physically or psychologically, or both. Low molecular weight drugs (about 150 amu to 500 amu) interact with macromolecule targets and induce appropriate biological responses.

The following characteristics can be used to categorise drugs:

  • Drugs are classified based on their pharmacological effects: The pharmacological effect describes how a substance or medicine affects or changes the cells of an organism. Different medications have different pharmacological effects on the body.

An analgesic, for example, relieves pain while an anti-inflammatory medicine lowers body inflammation. Drugs can thus be categorised according to their pharmacological action.

Drug Pharmacological Classification can be done as:

Based on their pharmacological effects on the body, drugs are divided into distinct classes. Let's take a closer look at each one individually.

  • Antacid:
    • We may experience stomach irritation and pain as a result of excessive acid production. This can sometimes result in stomach ulcers. 
    • Antacids were discovered to be effective in treating acidity. Antacids are chemicals that are used to neutralise stomach acids.
    • Acidity in the stomach causes heartburn, which can be relieved with antacids. They are given orally to reduce acidity's effects. 
    • Antacids are alkaline ions that neutralise gastric acids directly in the stomach. When we utilise too much hydrogen carbonate, the stomach becomes alkaline, which increases acid production. As a result, we use metal hydroxides that are insoluble and do not raise the pH over neutral.
    • In the treatment of hyperacidity, histamine was a big advance. In the stomach, histamine increases the release of pepsin and hydrochloric acid. 
    • Cimetidine (Tagamet) is a medication that prevents histamine from connecting with receptors in the stomach wall. As a result, there was less acid released.

Drugs with Neurological Activity: Neurologically active drugs change the way a message travels from the nerve to the receptor. Tranquillizers and analgesics are the two categories.

  • Analgesic:
  • Analgesics diminish the effects of pain without producing mental disorientation, paralysis, or other nervous system disruptions, so you can genuinely get rid of the pain without generating any nervous system imbalance. 
  • Analgesic medicines can affect the peripheral or central nervous systems in a variety of ways, but unlike anaesthetics, they do not erase pain sensations.
  • Aspirin and paracetamol are the most commonly used Analgesic. The structure of aspirin is drawn below:

  • Tranquillizers:
  • Anti-anxiety medication is referred to as a tranquillizer. In 1953, the phrase was coined to describe medications that have a soothing effect.
  • They are chemical substances that are effective in treating stress and mild to severe mental illnesses.
  • They provide a sense of well-being by removing stress, tension, anxiety, and aggravation from a person's life. They are one of the most important ingredients in sleeping medicines.
  • One of the most important hormones is noradrenaline. neurotransmitters are involved in mood alterations if the number of noradrenaline levels is low for some reason, signal-sending activity is reduced and the individual suffers from depression.
  • Examples are 

  • Antihistamines:
  • These are a class of medications that block histamine's physiological activity. Basophils create histamine, which is present in tissues that are close together. 
  • Histamine increases the permeability of white blood cells, allowing infections to enter diseased organs.
  • Example 

  • Anti-microbials:
  • Different sorts of organisms, such as bacteria, fungus, and viruses, can cause infections and diseases in humans and animals. Antimicrobial agents are drugs that prevent germs from becoming harmful.
  • Antimicrobial drugs are used to prevent pathogen-caused illnesses and diseases. Antimicrobial medications of various sorts are widely accessible. The following are some examples:Antibacterial medications are drugs that are used to prevent bacteria from causing disease. For example, Zithromax.
    Antifungal medicine: An antifungal drug is a drug that is used to prevent fungal activity in the host, for example, Miconazole


  • Antifertility drugs:
  • Antifertility medicines are chemicals that block the function of hormones that help one to get pregnant. 
  • These medications safeguard against pregnancy by lowering the chances of conception. Antifertility medicines are made up of synthetic progesterone derivatives or a combination of oestrogen and progesterone derivatives.
  • Example: Ethynylestradiol is a mixture of oestrogen and progesterone derivatives.


  • Drugs are classified based on their mechanism of action:
  • Distinct medications have different ways of eliciting a reaction, which is referred to as drug action. The manner in which a drug produces a response is more specific. 
  • There are several drugs to treat hypertension, but each type of drug has a different function. 
  • All hypertension medications work in a different method to lower blood pressure.
  • For example, Anti-histamines, are used to block the activities of histamines, which cause inflammation in the body.

  • Drugs are classified based on their chemical structure: 
  • This is a frequent drug classification. 
  • In general, medications with the same drug action and pharmacological effect have a similar skeletal structure with minor branching variations. 
  • As a result, certain medications have greater potential than others. For example, Sulphonamides, all have the same skeleton structure. Below is the structure of Sulphonamide.


Difference between drugs and medicine:

To answer this question, we must first consider the subject of purpose - particularly, what is the purpose of medicine and a drug?

A medicine's goal is to prevent, relieve, or cure a symptom, ailment, or disease state. In other words, a medicine's objective is benign; it's a product created and regulated to have a beneficial medical effect on a patient.

A drug also has a lot of different ingredients. In addition to the active component, medicines also contain excipients, which aid in the formulation and efficacy of the medication for the patient

Practice Problems:

Q1. Which of the following choices is used as a tranquillizer?

a. Sucralose
b. Saccharin
c. Equanil
d. Norethindrone

Answer: C
Equanil is a tranquillizer that is used to relieve anxiety for a brief period of time.A tranquillizer is a medicine used to treat anxiety, fear, tension, agitation, and mental problems, with the goal of reducing anxiety and tension.

Q2. Among which of the following is a narcotic analgesic?

a. Ofloxacin
b. Codeine
c. Saccharin
d. cimetidine

Answer: B
Codeine is a pain reliever that is used to treat mild to severe pain. It belongs to the class of drugs known as narcotic analgesics (pain medicines). To treat pain, this drug operates on the central nervous system (CNS).

Q3. Terfenadine is a class of

a. histamines
b. Antihistamines
c. Analgesics
d. Antibiotics

Answer: B
Terfenadine is an antihistamine that is used to treat allergy disorders. It is a bioprecursor prodrug. Sneezing, runny nose, itching and watering of the eyes, and other allergy symptoms are all prevented by antihistamines.

Q4. Aminoglycosides come under the branch of

a. Bacteriostatic antibiotics
b. Bactericidal antibiotics
c. Broad-spectrum antibiotics
d.  Limited spectrum antibiotics

Answer: B
Antibiotics such as aminoglycosides are used to treat serious infections caused by bacteria that proliferate rapidly or are difficult to treat. Bactericidal antibiotics are aminoglycoside antibiotics that destroy bacteria directly.

Frequently asked questions-FAQ

Q1. How did the early man use natural substances as medicines?

Answer: Early man used a variety of plants or parts of plants to treat ailments without understanding the chemical components that caused them. The bark of the willow tree, for example, was once used to treat pain (as an analgesic). Its bark was later discovered to contain 2-hydroxy benzoic acid, which is related to acetyl salicylic acid (also known as aspirin).

Q2. Can we use dyes to kill microorganisms?
Answer: Microorganisms can be killed by certain colours. These colours were among the first to be employed as antiseptics. Acriflavine (a yellow coloured dye), mercurochrome (a red coloured dye), and methylene blue are among examples (a blue coloured dye). Antiseptics are still made with these colours.

Q3. Is phenol a disinfectant or an antiseptic?
Answer: It's worth noting that a 0.2 percent aqueous phenol solution is used as an antiseptic by producing. In low doses, it is safe to use on living tissues (less than 0.2 percent).

When phenol concentrations are excessive, it can cause tissue damage. As a result, phenol is employed as a disinfectant at larger concentrations (1 percent or more).

Q4.What do you mean by Downer drug?
Answer: Downer slang phrase refers to CNS depressants, which are drugs that cause sedation by decreasing the transmission and reception of messages between the central nervous system and the brain. They make the person feel drowsy or relaxed, and they are often very successful at reducing pain. Downers, the polar opposites of uppers, reduce attentiveness and focus.

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