Pharmacology is the subject of understanding pathology and the required drugs. KD Tripathi is the best book for it. Each chapter in KDT has an initial part related to diseases and then there are strategies given to treat them. Most of the concepts are explained quite clearly and in a format which can be written in examinations. 

Whereas, Shanbag explains a lot of the concepts in a much simpler way and students score well in examinations. However, there are mistakes that are mostly corrected in KDT. Initially, it can be difficult to read chapters from KDT. But eventually, you will get used to it. 

So, I will advise you to use KDT as standard and use Shanbag as a reference. Also, make sure to correct the wrongly mentioned things during reading.