My question is related to the alcohol used in medicines. Is it produced synthetically or from grapes /sugar? What is the most common form of alcohol used in medicines?
Ethyl alcohol is the most common type of alcohol used in medication. In addition, it is a major component of many cosmetics, toiletries, cleaning supplies and countless other products. It is essential in the manufacture of many different drugs including vaccines, tinctures, syrups etc...
Ethyl alcohol is also available over the counter in a denatured form, meaning it contains contaminants (i.e. denaturants) that make the product unfit for oral consumption. The most common types of over the counter ethyl alcohol include 70% denatured ethyl alcohol and 90% denatured ethyl alcohol. These are often known as 'rubbing alcohol'. Isoproyl alcohol can also be referred to as 'rubbing alcohol'.
Ethyl alcohol is sometimes referred to as 'grain' alcohol as it can be produced from grains (e.g. corn, wheat), how we commonly identify alcohol being produced naturally. Due to various factors such as quality of grain, pricing etc... ethyl alcohol is often synthesized from natural gas instead.
The majority of ethyl alcohol is synthesized from ethylene, a natural gas. In you are interested in the complete manufacturing process of ethyl alcohol from ethylene, you may visit this link which details the process: http://www.itecref.com/pdf/Ethyl_Alcohol_Handbook_Equistar.pdf
In regards to knowing where the ethyl alcohol comes from in a specific medication, there would be no way to know without contacting the manufacturer directly. Most likely, it would be the synthesized version.