IMPURITIES AN OVERVIEW

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About Authors:
Lila dhar*, Prof. Sanjeev Thacker, Jatin Patel
Seth G. L. Bihani S.D. College Of Technical Education, Institute Of Pharmaceutical Sciences & Drug Research,
Gaganpath, Sri Ganganagar, Rajasthan 335001
*ldbudania@gmail.com

ABSTRACT
Impurities is defined as an entity of drug substances or drug product that is not chemical entity defined as drug substances an excipients or other additives to drug product. In pharmaceutical world, an impurity is generally considered as an other organic material beside the other drug substances that is arises out of the synthesis most of the time, inorganic contaminants are not considered as an impurity unless they are toxic, such as heavy metal or arsenic. There are numerios source of impurities and many different common terms are use for impurities such as by product, intermediate, transformation on product, related product, interaction product and degradation products.

Reference Id: PHARMATUTOR-ART-1533

INTRODUCTION
The control of pharmaceutical impurities is currently a critical issue to the pharmaceutical industry. Structure elucidation of pharmaceutical impurities is an important part of the drug product development process. Impurities can have unwanted pharmacological or toxicological effects that seriously impact product quality and patient safety. Potential sources and mechanisms of impurity formation are discussed for both drugs. The International Conference on Harmonization (ICH) has formulated a workable guideline regarding the control of impurities. In this review, a description of different types and origins of impurities in relation to ICH guidelines and, degradation routes, including specific examples, are presented. The article further discusses measures regarding the control of impurities in pharmaceuticals substance and drug product applications¹.

Impurities in pharmaceuticals are the unwanted chemicals that remain with the active pharmaceutical ingredients (APIs), or develop during formulation, or upon aging of both API and formulated APIs to medicines. The presence of these unwanted chemicals even in small amounts may influence the efficacy and safety of the pharmaceutical products².

According to ICH, an impurity in a drug substance is defined as-“any component of the new drug substance that is not the chemical entity defined as the new drug substance”. There is an ever increasing interest in impurities present in APIs recently, not only purity profile but also impurity profile has become essential as per various regulatory requirements. The presence of the unwanted chemicals, even in small amount, may influence the efficacy and safety of the pharmaceutical products¹.

“In the pharmaceutical world, an impurity is considered as any other organic material, besides the drug substance, or ingredients, arise out of synthesis or unwanted chemicals that remains with API’s”

The control of pharmaceutical impurities is currently a critical issue to the pharmaceutical industry. The International Conference on Harmonization (ICH) has formulated a workable guideline regarding the control of impurities.

CLASSIFICATIONS OF IMPURITIES:
Impurities have been named differently or classified as per the ICH guidelines as follows¹:

A] Common names
1. By-products
2. Degradation products
3. Interaction products
4. Intermediates
5. Penultimate intermediates
6. Related products
7. Transformation products

B] United State Pharmacopeia
The United States Pharmacopoeia (USP) classifies impurities in various sections:
1. Impurities in Official Articles
2. Ordinary Impurities
3. Organic Volatile Impurities

C] ICH Terminology
According to ICH guidelines, impurities in the drug substance produced by chemical synthesis can broadly be classified into following three categories –
1. Organic Impurities (Process and Drug related)
2. Inorganic Impurities
3. Residual Solvents

Organic impurities may arise during the manufacturing process and or storage of the drug substance may be identified or unidentified, volatile or non-volatile, and may include
1. Starting materials or intermediates
2. By-products
3. Degradation products

Impurities are found in API’s unless, a proper care is taken in every step involved throughout the multi-step synthesis for example; in paracetamol bulk, there is a limit test for p-aminophenol, which could be a starting material for one manufacturer or be an intermediate for the others. Impurities can also be formed by degradation of the end product during manufacturing of the bulk drugs.

The degradation of penicillin and cephalosporin are well-known examples of degradation products. The presence of a β-lactam ring as well as that of an a-amino in the C6 or C7 side chain plays a critical role in their degradation.

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