Classification Of Drugs and Categories

Drugs are part and parcel of our lives; they have a very important role in maintaining our health, treating illnesses, and improving our well-being. From simple painkillers like aspirin to take away a headache to the very complex chemotherapeutic agents in fighting an innumerable number of cancer patients, drugs have become an integral part of the armamentarium of modern medicine. However, with such vast numbers of drugs, it becomes important to understand how they are actually categorized and what these classifications do.

This Story also Contains

1. Basics of Drugs Classification
2. Classification of Drugs
3. Types of Drug Classifications
4. Need for Classification of Drugs
5. Some Solved Examples
6. Summary

Basics of Drugs Classification

Drug classification—this is the grouping of the arrangement of drugs according to established features: the structure, mechanism of action, therapeutic effect, and pharmacological features. It is the science approach to make it easier for proper understanding by practitioners, researchers, and policymakers on different drugs and features, predictions, and possibilities for interaction, for reasoned use.

One of the most broadly applied classifications, for example, is the Anatomical Therapeutic Chemical classification developed by WHO. This class categorizes drugs based on their target organ or system and their therapeutic, pharmacological, and chemical properties. An example is cardiovascular disease drugs, classified under the "C" group, which then further classifies the nervous system drugs as part of the "N" group.

All medicines are drugs but all drugs are not medicines. A drug may be habit-forming, causing addiction while a medicine is safe to use and does not cause addiction. Drugs may be a single chemical substance or a combination of two or more different substances. An ideal drug should satisfy the following requirements:

• When administered to the ailing individual or host, its action should be localized at the site where it is desired to act. In actual practice, there is no drug that behaves in this manner.
• It should act on a system with efficiency and safety.
• It should have minimum side effects.
• It should not injure host tissues or physiological processes.
• The cells should not acquire resistance to the drug after some time.

Classification of Drugs

Drugs may be classified in a number of different ways. Some of these are mentioned below:

1. On the basis of pharmacological effect:

This classification is based on the pharmacological effect of the drugs. It is useful for doctors because it provides them with the whole range of drugs available for the treatment of a particular disease or infection. For example, analgesics have pain pain-killing effect while antiseptics kill or arrest the growth of microorganisms.

2. On the basis of drug action:

It is based on the action of a drug on a particular biochemical process. For example, all antihistamines inhibit the action of histamine which causes inflammation in the body. There are various ways in which the action of histamines can be blocked.

3. On the basis of chemical structure:

It is based on the chemical structure of the drug because drugs have common structural features and often have similar pharmacological activity. For example, sulphonamides having common structural features as given below are mostly antibacterial.

Types of Drug Classifications

There are many ways in which drugs may be classified. On these grounds, different drug types can also be seen divided by:

1. Chemical classification: Categorization of the drugs based on their chemical structure; that is to say, alkaloids, steroids, or phenothiazines would be exemplary.

2. Therapeutic classification: Drugs may also be classified on the basis of their class of therapy, such as analgesics—pain relievers, antibiotics, and antidepressants.

3. Pharmacological classification: Based on mechanism of action, for example, alpha-blockers, beta-blockers, or proton pump inhibitors.

4. Adverse effect classification: Based on the type of side effects the drug can cause, like drugs causing sedation or drugs acting on the cardiovascular system.

Need for Classification of Drugs

1. Better safety of patients: Relationship complexities between different drugs aid the health professional in predicting and dealing with probable drug interactions, thereby reducing the occurrence of side effects.

2. Faster drug development: Drug classification will help in rapidly identifying potential drug candidates by showing similarities to that of existing drugs.

3. Effectual treatment planning: Drug classification by the health professional helps in the selection of the most appropriate drug to an individual's malady and, at the same time, takes into account the special requirements of the patient.

4. Compliance with regulatory bodies: The classification of drugs allows the regulating bodies, like the Food and Drug Administration (FDA) or European Medicines Agency (EMA), to control which drugs ensure their safe and effective use.

Some Solved Examples

Example 1:

Matching Drugs with Their Therapeutic Actions

Question:
Match the following drugs with their therapeutic actions:

(i) Ranitidine
(ii) Nardil (Phenelzine)
(iii) Chloramphenicol
(iv) Dimethane (Brompheniramine)

(a) Antidepressant
(b) Antibiotic
(c) Antihistamine
(d) Antacid
(e) Analgesic

Solution:
(i) Ranitidine $\longrightarrow$ (d) Antacid
(ii) Nardil (Phenelzine) $\longrightarrow$ (a) Antidepressant
(iii) Chloramphenicol $\longrightarrow$ (b) Antibiotic
(iv) Dimethane (Brompheniramine) $\longrightarrow$ (c) Antihistamine

Hence, the answer is option (2).

Example 2:

Deficiency of Nor-Adrenaline

Question:
If a person is suffering from a deficiency of noradrenaline, what kind of drug can be suggested?

1) Anti-inflammatory
2) Antidepressant
3) Antihistamine
4) Analgesic

Solution:
Noradrenaline is a neurotransmitter. If nor-adrenaline is low, a person may suffer from depression. Hence, an antidepressant drug is suggested.
Therefore, the answer is option (2).

Example 3:

Drugs Used for Therapeutic Purposes

Question:
Drugs that are used for therapeutic purposes are generally called?

1) Enzymes
2) Receptors
3) Chemical Messengers
4) Medicines

Solution:
Medicines are drugs that are used for therapeutic purposes like diagnosis, prevention, and treatment of diseases.
Hence, the answer is option (4).

Example 4:

Classification of Drugs for Medicinal Chemists

Question:
The most useful classification of drugs for medicinal chemists is:

1) On the basis of chemical structure
2) On the basis of drug action
3) On the basis of molecular target
4) On the basis of pharmacological effect

Solution:
One of the methods of classification of drugs is based on molecular targets. Drugs possessing some common structural features may have the same mechanism of action on targets. The classification based on molecular targets is the most useful classification for medicinal chemists.
Hence, the answer is option (3).

Example 5:

Identifying Drug Molecule Structure

Question:
The structure shown below is of which well-known drug molecule?

1) Ranitidine
2) Seldane
3) Cimetidine
4) Codeine

Solution:
The given structure is of Cimetidine, which is a well-known drug molecule.
Hence, the answer is option (3).

Summary

By their very nature, the classifying of drugs represents the cornerstone of pharmacology and medicine. It structures the understanding and the probable usages of the different medicines. When one learns about the various classifications of drugs, one can only appreciate the complexity and importance of this area and how the usage of drugs could be assured to be safe and effective for one's health.