Dear Maryam,

You have really asked a great question but unfortunately there is no direct answer to your  question as function alone not only plays determining role for a chemical compound to be considered as a drug or potential to be a drug. There are several factors like IC50, toxicity, detoxification mechanisms, risk-benefit ratio, short term and long term side effects, teratogenicity, carcinogenecity, mutagenicity etc need to be evaluated for a safer selection of drug.

I am not aware of any organized data base which alone can help you understanding and determining the selection criteria of drugs based on function. Rather there are several resource materials available online that you can consider for gaining basic to moderate knowledge in this area.

As a ready reference I am sharing with you a combined pdf file which I believe will be worth reading.

Hope that helps!

 the merck-index  is one standard option http://www.pharmagupshup.in/2010/11/merck-index-14th-edition-free-download.html

Dear Amritlal and Yannis

Thanks for your suggestions.

The most important thing that I should know about the drugs is the function of their targets, I should know which drugs target the genes in the signaling pathways and which drugs, for example, just target ion channels. I am searching  databases that explain about drug and their targets.

Best, Maryam

Dear Maryam, 

I believe there is no direct solution to your question, and to my knowledge there is no ready made database if you to stick only to the function .What i would suggest is to filter a key word(s) under (pharmacodynamics) ,this may help you. All the best.