An Introduction to Drug Chemical Agents
A drug is any chemical substance that brings about changes in the functioning of living organisms. Pharmacology is the science that studies and deals with drugs in medicines and their mechanism of action, physical and chemical properties, metabolism toxicity and therapeutics. Principles of drug action and different types of drugs are used in the treatment and prevention of diseases in human beings
A branch of medicine and pharmaceutical sciences concerned with drugs or the aftereffect of medicine, where a drug may be defined as any artificial, natural, or endogenous molecule which exerts a physiological or biochemical effect on the cell, tissue, or organ of the body. To be more specific we can say that it is the study of the interactions that occur between a living organism and chemicals that affect biochemical processes. Substances possessing medicinal properties are considered pharmaceuticals.
Types of Pharmacology
Pharmacology has the following Branches:
1. Pharmacokinetics: It describes what our body does to a drug, referring to the movement of the drug in our body, through the body and out of the body. This process usually occurs in 4 phases in pharmacokinetics.
Absorption
Distribution
Metabolism
Excretion
Sometimes known by the acronym 'ADME'.
2. Pharmacodynamics: It is just the opposite of what pharmacokinetics is, it describes what a drug does to our body or how our body responds to the drug.
The study of the physiological, molecular and biochemical effects of drugs on the human body involves the study of post-receptor effects, chemical interactions and receptor bindings. Together pharmacokinetics and pharmacodynamics build a dose-response relationship.
Types of Drugs and Their Uses
Medicinal drugs are chemical drugs divided into different groups or classes based on their uses, chemical structure or mode of action. These classification systems are sometimes confusing as one drug type may be included in more than one class.
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Antimicrobial Drugs: Drugs are used for the prevention or treatment of diseases caused by microbes like bacteria, fungi, protozoa, viruses or helminths. They contain chemical substances which kill or reduce the metabolic products produced by the microorganisms. Antibiotics come under the category of antimicrobial drugs. Example- penicillin.
Immunosuppressants: Immunosuppressants are a group of medicines used to block the immune response and are generally administered to patients who have undergone organ transplantation or are suffering from an autoimmune disease. Some of the common immunosuppressants are drugs that contain polyclonal antibodies, monoclonal antibodies, glucocorticoids, etc.
Drugs that Affect Blood: There are drugs that have to activate or inhibit enzymes that are involved in the regulation of blood clotting within the blood vessels. These drugs are administered in conditions like atherosclerosis or any kind of blockage in arteries occurring in the blood flow. There are various drugs like anticoagulants, antiplatelet drugs and fibrinolytic drugs which are involved in controlling the coagulation process.
Cardiovascular Drugs: These affect the functioning of the heart and blood vessels. They are administered for cardiovascular diseases like hypertension, and atherosclerosis. These drugs also affect the functioning of the heart muscles, frequency and regularity of heartbeat, etc.
Endocrine Drugs: Drugs that are used to treat endocrine abnormalities. Their functioning includes changes in the regulation of the hormonal axis, effects on hormonal transport, as well as similar changes to counter-regulatory hormone systems. Endocrine drugs are used for the treatment of thyroid, Addison disease, etc.
Reproductive Drugs: These affect the functioning of our reproductive system. These drugs are used for treating reproductive diseases.
Central nervous system drugs: These affect the functioning of the central nervous system. These drugs are administered in order to produce changes in behaviour, a physical sensation or mental state. Local anaesthetics, on the other hand, induce a loss of sensation in just one area of the body by blocking conduction in nerves at and near the injection site.
Digestive System Drugs: These groups of drugs act on the digestive system by affecting the actions of the involuntary muscle (motility) and thus altering movement or also by altering the secretion of digestive juices or gastric emptying. Examples of major groups of digestive drugs include antidiarrheal drugs, laxatives, antiemetics, emetics, proton pump inhibitors, and antacids.
Dermatologic Drugs: Topical application of drugs provides a direct, localized effect on a specific area of the skin. When these drugs are applied to the skin, they may be dissolved in a variety of formulations, ranging from simple solutions to greasy ointments. These medications can relieve itching, exert a constricting or astringent action on the pores, or dissolve or remove the epidermal layers. The skin can be affected by other means like photosensitizing drugs, and pigmenting agents (psoralens).
The chemical drugs list can be endless. There are numerous drugs for various diseases. These drugs are of vital importance to humankind. The knowledge of pharmacology and drugs is also indispensable to medical science. It helps create wonders in the human body and soothe numerous ailments.
Did You Know?
Drugs are often abused by people. Adolescence is a period when a lot of people indulge in drug abuse and dependency. This can be due to experimentation, curiosity or even depression. This can cause serious issues which lead to severe consequences and even death. Drugs abused are opioids, cannabinoids, coca alkaloids, etc. These when taken in overdose can cause life-threatening damages.
FAQs on Types of Drugs
1. What are the main ways drugs are classified as per the CBSE 2025-26 syllabus?
Drugs are primarily classified based on four key criteria to help understand their applications and properties:
- On the basis of Pharmacological Effect: This classification is based on what the drug does to the body. For example, analgesics reduce pain, while antiseptics prevent microbial growth.
- On the basis of Drug Action: This refers to the specific biochemical process the drug targets. For instance, all antihistamines work by inhibiting the action of the compound histamine.
- On the basis of Chemical Structure: Drugs with similar chemical structures often have similar pharmacological activity. For example, sulphonamides all share a common structural feature.
- On the basis of Molecular Targets: Drugs interact with biomolecules like proteins, carbohydrates, lipids, and nucleic acids, which are called target molecules or drug targets. This is the most useful classification for medicinal chemists.
2. What are analgesics, and how are they categorised?
Analgesics are a class of drugs that reduce or abolish pain without causing impairment of consciousness, mental confusion, or paralysis. They are broadly categorised into two main types:
- Non-narcotic (non-addictive) analgesics: These drugs, like aspirin and paracetamol, are effective for relieving skeletal pain such as that due to arthritis. They also have antipyretic properties (fever-reducing).
- Narcotic analgesics: These drugs, such as morphine and codeine, are primarily used for relief from postoperative pain, cardiac pain, and pain of terminal cancer. However, they are habit-forming and can be addictive if used improperly.
3. What is the primary difference between an antiseptic and a disinfectant?
The primary difference between an antiseptic and a disinfectant lies in where they are applied. Antiseptics are chemical agents applied to living tissues, such as skin, wounds, and cuts, to either kill or prevent the growth of microorganisms. Examples include Dettol and Savlon. In contrast, disinfectants are applied to inanimate objects like floors, instruments, and drainage systems to kill microorganisms. They are generally not safe for application on living tissues due to their higher concentration and toxicity.
4. Why are broad-spectrum antibiotics not always the preferred choice for treating bacterial infections?
While broad-spectrum antibiotics are effective against a wide range of gram-positive and gram-negative bacteria, they are not always the best choice. This is because they do not just target harmful bacteria; they can also kill the beneficial bacteria that naturally reside in the body (e.g., in the gut). Eliminating these useful bacteria can disrupt the body's natural balance, leading to secondary health issues. It is often better to use a narrow-spectrum antibiotic that specifically targets the identified pathogenic bacterium, minimising collateral damage to the body's normal flora.
5. How can the same chemical substance, like phenol, function as both an antiseptic and a disinfectant?
A chemical substance's therapeutic action can critically depend on its concentration. Phenol is a classic example of this principle. In a low concentration, such as a 0.2% solution, phenol acts as an antiseptic, making it safe for application on living tissues. However, in a higher concentration, like a 1% solution, its action becomes more potent and corrosive, making it suitable only as a disinfectant for cleaning non-living surfaces.
6. How do tranquillisers and analgesics differ in their effect on the body’s nervous system?
Tranquillisers and analgesics are both neurologically active drugs, but they affect the nervous system differently. Tranquillisers are used to treat stress, anxiety, and mild to severe mental diseases. They work by affecting the mechanism of message transfer from nerve to receptor, inducing a sense of well-being and calmness. In contrast, analgesics specifically target and suppress the pathways of pain signals in the nervous system, reducing the sensation of pain without necessarily altering a person's mental state or causing sedation, unless they are of the narcotic variety.
