Classification of Drugs

A drug is defined as a chemical substance that is used as a medication for the diagnosis or treatment of a disease. Classification of drugs is very important because in the last decades, there has been an emergence of many drugs. These drugs are very diverse and their effect, chemical structure, function, and side effects vary a lot. Hence, systematic study and understanding of the classification of drugs are required. Drug classification helps to guarantee that drug use is advantageous and safe. This is also useful for clinical trials and for chemists.

What are Drugs?

Drugs are chemical substances that are given to a person when they are ill. Drugs help in minimising abnormal effects, pain, or any symptoms related to diseases. Many drugs act by affecting the nervous system. Though with many benefits, drugs also bring many disadvantages such as side effects, adverse reactions, addiction, or resistance. Taking many drugs at a time makes a person’s response to a particular drug. 

Classification of Drugs

There are many classification methods available in the system for drugs. The drugs could be classified based on pharmacological and therapeutic effects. Here, drugs are classified based on the chemical structure, action of drug pharmacologic effect, and molecular target.

Based on Chemical Structure

Many drugs have similar structures or there is a slight difference in molecular structure. Such drugs are included in one group. These types of drugs are found to exert a similar function on the body. A similar structure included in these drugs is the functional group. For example, sulphonamide, barbiturates, etc. have a similar structure.

Based on Drug Action

Drugs are also classified based on the action of a particular drug on the body. Different drugs have different modes of action on the body and produce body responses for the ailment of illness. Many drugs act in a different mechanism but produce a similar effect. Such drugs are included in this group. One such example is drugs taken for hypertension. There are many drugs for the treatment of hypertension but all have a different mode of action. Another example is an antihistamine which is taken during inflammation caused by histamine. Antihistamines block the action of histamine hence preventing inflammation. 

Based on Pharmacological Effect

Pharmacology is the science that studies understanding the action of drugs on the biological system and the response of the body to drugs. They are based on how they affect and minimise symptoms in the body. 

Based on the Molecular Target

Some drugs are specific to targets in the body. They either block this target or initiate a cascade for the treatment. Some drugs target include protein, lipid, carbohydrates, nucleic acids, or any other such biomolecules. Many drugs can target the same molecule and will have the same mechanism of action.

Classification of Antihypertensive Drugs

Hypertension is a condition where a person’s blood pressure is elevated from the normal range. People suffering from hypertension take antihypertensive drugs. These drugs bring elevated blood pressure to a normal level. There are many antihypertensive drugs based on the mechanism and effect of drugs.

The four major classes of antihypertensive drugs are following:

Diuretics

They reduce sodium absorption in the nephron. Thereby loss of sodium and water in urine. These drugs maintain blood pressure by increasing urination. Example, hydrochlorothiazide, Bumetanide, Furosemide, etc.

β-blockers

β-blockers are drugs that are used by hypertensive patients. These drugs block the target site for norepinephrine, catecholamine, and epinephrine. For example, Bisoprolol, Nebivolol, etc.

Calcium Channel Blockers

Calcium is the substance that makes the arteries and heart walls contract more strongly. Hence, blocking the calcium will provide relaxation to muscles. Hence, Calcium blockers are used for a patient suffering from high blood pressure. Examples are clevidipine, lercanidipine, nifedipine, etc.

Renin-Angiotensin System Inhibitors 

This group also includes angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. These are involved in blocking all the enzymes involved in the production of angiotensin II. Example: delapril, benazepril, etc.

Classification of Drugs in Pharmacology

These groups are classified based on the type of effect they have on the body. Some groups based on pharmacologic classification are analgesics, antibiotics, and antiseptics. These are grouped according to the symptoms they cure. For example, analgesics relieve body pain, some examples of analgesics are Hydrocodone and methadone. Antibiotic drugs treat bacterial and fungal infections. Examples of antibiotics are penicillin, cephalosporin, etc.  Antiseptics are a group of drugs that will kill germs and microorganisms. Examples of antiseptics include chloroxylenol, hydrogen peroxide, etc. Some other examples include antacids that reduce acidity in the stomach for example-aluminium and magnesium hydroxide.

Key Features 

• These are a few parameters on which drugs are classified. Drugs are classified based on chemical structure, drug action, pharmacologic effect, molecular target, and therapeutic parameters.

• One drug could be included in more than one group. The pharmacological classification includes drugs which treat a particular condition such as antacids, antiseptics etc. 

• Antihypertensive drugs include diuretics, β-blockers, calcium channel blockers, etc.