Dear aspirant hope you are doing well..

The report was found stating, "Since these medicines are costly as compared to government supplies, doctors earn up to 40% commission from medical store owners."

A good doctor or generally most of doctors do not prescribe you a sub-standard medicine for their little extra commission, because they know eventually it will give a big dent in one's practice and reput. And moreover it is not their primary source of income, they have many more. Pharmaceutical company give incentive to a doctor just because he is prescribing their product among so many brands, so it is just treat to them to keep prescribing their good product for relevent illnesses.

So being a patient you need not to worry about brands and commission.
The only thing to ensure is your doctor make a good diagnosis of your illness and prescribe relevant medicines.

Hope it's helpful thank you