Classification of Drugs

Medicinal Chemistry is one of the important branches of chemistry. In today’s world, when a virus is the biggest threat to humanity, it becomes even more important to have a concrete base of Medicinal Chemistry. Under the threat of novel coronavirus, we all understand very clearly that if we do not have effective drugs or vaccines against viruses then diseases caused by them become pandemic very soon. In today’s times, there is no need to explain the importance of drugs. As we all know, up to which extent drugs can change our lives. 

Any chemical or synthesized chemical substance when taken into the body alters the function of the body, either physiologically, mentally or psychologically. When drugs are used for healing a disease are called medicines. These are generally chemicals of low molecular masses (100-500u). Over consumption of drugs can be lethal. 

Classification of Drugs 

Medicinal science has discovered numerous drugs for various purposes. Drugs can be classified into four broad categories –

  • Based on pharmacological effect 

  • Based on Drug action 

  • Based on chemical structure 

  • Based on molecular targets 


Based on pharmacological Effect – Drugs are classified into various types on the basis of their pharmacological effects. This class of drugs provides doctors a whole range of drugs for a particular problem. For example, analgesics, antiseptics and disinfectants etc. 

Based on Drug Action – Drugs are classified into many types based on their action on a particular biochemical process. Biochemical processes take place in the human body. But sometimes in the body these processes occur to a larger extent than required. At that time, we need a drug to control the process. For example, antihistamine drugs reduce the production of histamine as over production of histamine causes allergies and inflammation in the body. 

Based on Chemical Structure – Drugs are classified on the basis of their chemical structure. Drugs under this category share common structural features. These drugs generally have similar pharmacological activity as well. For example, all sulfonamides drugs have similar structural features as shown below. These are also called sulpha (sulfa) - drugs.

Similar structure present in both above sulpha - drugs is –

Based on Molecular Targets – Drugs are classified according to their drug targets as well. Some drugs target carbohydrates, some lipids and some proteins. Generally, drugs with similar structures target similar molecules and they possess similar mechanisms of action of targets as well. It is the most useful classification for medicinal chemists. For example, Statins and Niacin interact with lipid biomolecules. 

Therapeutic Action of Different Classes of Drugs 

  • Antihistamines – These drugs work against histamine. Some people suffer hypersensitivity to dust, due to release of histamine in their body. Antihistamine drugs are used for allergies, fever, sneezing etc. 

  • Antacids – Over production of acid in the stomach causes irritation, pain or even ulcers in the stomach. Antacids neutralizes the excess of acid produced in the body. Thus, these drugs help to maintain the pH in the stomach. For example, magnesium oxide is an antacid. 

  • Neurologically Active Drugs – These drugs work on the message transfer mechanism from nerve to receptor. For example, Tranquilizers and Analgesics are neurologically active drugs. Antidepressant drugs also come under this category. Tranquilizers are used for treatment of stress. Analgesics reduces pain without causing impairment of consciousness, mental confusion and disturbance in the nervous system. 

  • Antimicrobials – These drugs inhibit the growth of disease-causing microorganisms in the body. Bacteria, viruses, fungi etc. causes many diseases in human beings and animals as well. For the treatment of pathogenic action of microbes in the body, many kinds of antimicrobial drugs have been discovered. For example, antibacterial drugs work against bacteria, antifungal drugs work against fungi, antiviral drugs work against viruses, antiparasitic drugs work against parasites selectively. Antibiotics, antiseptic and disinfectants are antimicrobial drugs. 

  • Antifertility Drugs – These are the drugs which are used for family planning. Birth control pills come under antifertility drugs. These pills essentially contain a mixture of synthetic estrogen and progesterone derivatives. 


Classification of drugs is a vast topic; it was a brief on classification of drugs to give an idea about various classes of drugs. If you are looking for detailed study notes on various topics of Chemistry, then log on to Vedantu website or Download Vedantu learning app.