Residual solvents in pharmaceuticals are defined as organic volatile chemicals

that are used or produced in the manufacture of drug substances or excipients, or in

the preparation of drug products. They are not completely removed by

practical manufacturing techniques. For more information read the ICH guide where you will find out about the limits accepted of the residual solvents, their classification, etc. 

http://www.ich.org/fileadmin/Public_Web_Site/ICH_Products/Guidelines/Quality/Q3C/Step4/Q3C_R5_Step4.pdf

 Hi Mohamed Alaoui

The need for Residual solvent is there even after getting the finished product.

The reason may be the process may which the material is made up of.

Source of Residual Solvent contamination:

1. API source/ API manufacturing process.

2 The process of finished product manufacturing.

3. Cleaning of instrument/ Equipment's.

So if organic solvent is used in any process of development one has to limit that by a specific Analytical method.

If you have any further query feel free to ask... 

Residual solvent arises from the processing involved. As Hitesh listed out the possibilities of residual solvents, it is the cause of residual solvent in the finished product. organic solvents has to be avoided mostly in the pharmaceutical processes and if unavoidable that has to be fixed within the limit in the finished product. ICH guidelines fixes classifies the  solvents as

1. solvents to be avoided

2.solvents to be limited

3. solvents with low toxic potential

4.solvents for which no toxicological data was found.

and fixes the limit for them.

just check this link.

http://www.ich.org/fileadmin/Public_Web_Site/ICH_Products/Guidelines/Quality/Q3C/Step4/Q3C_R5_Step4.pdf

Perfectly Well said Sanmugapriya,

If you have an API which is having some Residual Solvent in it, then You have to perform the residual solvent check to make sure there is no extra solvent being added by the process.

And If your process has some organic solvent in it then you have to prove that the finished product doesn't contain the residual solvent more than the given limits in ICH Guidelines

Also, there are some excipients in which the organic solvent is used during manufacturing. So because of that also one has to monitor the Organic solvent Content in the finished product.

The impurities in Pharmaceuticals are regulated by Food and Drug Administration (FDA) and International Conference on Harmonization (ICH) guidelines. Because many solvents pose a major risk to human health, national and international regulatory bodies such as the United States Food and Drug Administration (U.S. FDA), the United States Pharmacopoeia (USP), the European Pharmacopoeia (EP), and the International Conference on Harmonization (ICH) require analysis for residual solvents in pharmaceutical drug substances, excipients and final products. In herbals,residual solvents may results from their use as an extraction solvent in liquid extracts and tinctures or when added as a diluents to liquid pharmaceutical preparation.

http://ijrrpas.com/wp-content/uploads/2012/11/Regulatory-And-Analytical-Aspects-Of-Residual-Solvents-In-Ayurvedic-Formulations-A-Recent-Update.pdf

My Question is if API having the residual solvent and if we are preparing the DRY POWDER INJECTION, shall We do the residual solvent validation for the finished product as of now API manufacturer is control the residual solvent by testing.