D Pharma is a Diploma course. With that you cannot appear for UPSC. But BA is a Bachelor's degree and you can appear for UPSC on the basis of BA in Political Science. Considering the fact that D Pharma is pursued after  10+2, you can pursue BA in PolitIcal Science and still be eligible for UPSC. For appearing in UPSC, you should have completed your Graduation in any discipline. So you can pursue BA in Political Science through Distance Education and still be eligible for UPSC.