Pharmacognosy- Classification of Drugs

Table of Contents

Introduction

There are thousands of plant species used as medicine. The drugs used in Indian traditional systems of medicines are 90% based on plant sources. These drugs are considered to be safe, cost effective and having minimal side effects. To study the individual drug, from variety of drugs sources and their uses, one must use a systemic sequence of arrangement. Classification of drugs clear the confusion of due to diversity of drugs. In this article we will see the various classification of drugs which helps to simplify understanding of drugs.

Classification of drugs

A method used for drug classification must possess following properties,

Simple
Easy to use
Free from confusion and ambiguities

$\"Classification$

Drugs are classified in different ways; each classification has its own advantages and disadvantages. Drugs are classified in following different ways;

Alphabetical classification
Morphological classification
Taxonomical classification
Chemical classification
Pharmacological classification
Chemo-taxonomical classification
Sero-taxonomical classification

Alphabetical classification

It is the simple way drug classification. In this drug are arranged according to alphabetical order of their Latin and English names (common names) or local names (vernacular names). Some important pharmacopeia’s, dictionaries and reference books use this classification.

Indian pharmacopeia
British pharmacopeia
British herbal pharmacopeia
United state pharmacopeia
British pharmaceutical codex
European pharmacopeia

In European pharmacopeia drugs are arranged according to their Latin terms and in United state pharmacopeia and British pharmaceutical codex drugs are arranged to their English names.

Advantages

It is easy and fast to use.
There is no repetition of drugs which avoid confusion.
In this classification location, tracing and addition of new drug entries is easy.

Disadvantage

There is no relationship between previous and successive drug entries.

Morphological classification

In this system drugs are arranged according to morphological or external characters of the plants or animal parts. The drugs which are direct parts of the plant or animal and contain cellular tissue are called as organised drugs. For example, leaves, bark, hair, etc. The drugs which are obtained by some intermediate physical process like incision, drying or extraction and do not contain any cellular tissues are called unorganised drugs. For example, aloe juice, gelatin, honey, beeswax, etc.

Advantages

This method useful when chemical nature of drug is not clearly known.
It gives clear idea about the source of drugs.
This classification helpful to identify and detect adulteration.

Disadvantages

There is no relation with chemical constituents and therapeutic actions.
Repetition of drugs occurs.

Taxonomical classification

In this classification drugs are classified according to kingdom, subkingdom, division, class, order, family, genus and species. Taxonomical classification is a botanical and zoological classification of plants and animals respectively.

Example

Class: Angiospermae

Sub class: Dicotyledonae

Order: Rutales

Family: Rutaceae

Drug: Orange peel and lemon peel

Advantages

This system helps to study evolutionary developments of crude drugs.
Taxonomical ination gives details about species and varieties of organisms.

Disadvantages

This classification does not provide any ination related to chemical nature.
This system does not provide any correlation between chemical constituents and biological activity of drugs.
This also does not provide any ination about organised or unorganised nature of crude drugs.

Chemical classification

In this crude drug are classified according to the chemical constituent of it. For example,

Chemical constituent	Examples
Alkaloids	Vinca, belladonna, opium, tea
Glycosides	Senna, digitalis, aloe, wild cherry
Lipids	Castor oil, peanut oil
Volatile oils	Clove, coriander, fennel
Tannis	Catechu, galls
Vitamins	Yeast, cod liver oil, shark liver oil
Resin and resin combinations	Benzoin, guggul, shellac
Carbohydrates and derived products	Agar, honey, starch, acacia

Advantages

It is important for phytochemical studies.
Due to knowledge of chemical constituents, it is easy to study the use of drug.

Disadvantages

This method does not provide any idea about the source of drug and whether the drug is organized or unorganized.
Some drugs contain two or more chemical constituents, then it is difficult to classify them according to this method.

Pharmacological classification

In this classification crude drugs are classified according to pharmacological action of their important chemical constituent. For example,

Pharmacological action	Example
Anthelmintics	Quassia, male fern
Anti-amoebic	Kurchi, ipecacuanha
Antispasmodic	Datura, belladonna
Anticancer	Vinca, podophyllum
Bitters	Nux vomica, cinchona
Carminatives	Fennel, dill, clove
Cardiotonic	Digitalis, squill
CNS stimulant	Opium, tea
Purgative	Aloe, senna
Expectorant	Vasaka, nutmeg, liquorice
Astringent	Myrobalan, black catechu
Immunomodulatory agents	Ashwagandha, tulsi, ginseng
Antihypertensive	Rauwolfia

Advantages

This system helps to suggest substitutes of drugs if particular drug is not available at particular time and place.

Disadvantages

It is difficult to classify some drugs having two or more different pharmacological actions.

Chemo-taxonomical classification

The phytochemical screening of several drugs suggests that there is close relationship between chemical constituents of plants and its taxonomical status. In this method of classification equal importance is given to their taxonomy and chemical constituents. For example, berberine alkaloid in berberis and argemone, rutine in rutaceae.

Advantages

It gives more scope for understanding relationships between chemical constituents, their biosynthesis and possible action.

Disadvantages

This system fails to understand therapeutic nature of crude drugs.

Sero-taxonomical classification

This method is the application of serology (study of antigen and antibody reactions). The use serology to solve taxonomic problems known as Sero-taxonomy.

Advantages

This technique helps in the comparison of single proteins from different plants.

Disadvantages

This method of classification does not provide any ination about organised or unorganised nature of crude drugs.

Conclusion

Various crude drugs are obtained from natural sources are used in the treatment of diseases. For their adequate study it is necessary to arrange them in scientific and systematic manner. Classification of natural drugs help us to arrange and study them systematically. There are various methods of drug classification. Each one of them have some advantages and some disadvantages as we discussed above.

Introduction