Class of Solvents for pharmaceutical formulations

This article describes the Different class of solvents which are using in the pharmaceutical formulations

What is mean by Residual Solvents/Solvents ?

Residual solvents refer to volatile chemicals or solvents that may remain in a product or substance after a manufacturing or processing procedure. These solvents are typically used during the production process but are intended to be removed to safe levels before the final product reaches consumers. Residual solvents can pose health risks if they are present in significant quantities in the final product.

Class of solvents are classified in three types based on their toxicity and potential health risks

Class 1 Solvents :

  • These class of solvents known to be highly toxic to humans, and their presence in pharmaceuticals or other products is not acceptable. This class solvents are strongly suspected human carcinogens and environmental hazards.


  •  Benzene , Tetrachloromethane, Dichloroethane ,Trichloroethane. etc..

Class 2 Solvents :

  • These class of solvents have a lower level of toxicity but still need to be controlled to ensure they are within safe limits. Should be limited in pharmaceutical products because of there inherent toxicity.


  •  Dichloromethane, Chloroform, Methanol, Ethylene glycol. etc.

Class 3 Solvents :

  • These class of solvents have a low potential for toxicity and are considered less harmful. This class solvents known as human health hazard at level normally accepted in pharmaceuticals.
  • Many of the class 3 solvents long term toxicity and carcinogenicity study not available. Available data indicates that they are less toxic in acute or short term studies and negative in genotoxicity. It is considered amount of these residual solvents of 50 mg per day or  less which is corresponding to 5000 PPM.

         Examples :

  •  Isopropyl Alcohol, methyl acetate ethyl ether, Heptane etc..

For detailed information click here for US pharmacopoeia general monograph 467  

For detailed information click here for ICH Q3C (R6)- Guideline for residual solvents




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