what should be better to do after b.pharm ? MBA in pharma or pharm D

Well it depends, on what you are looking for from your career.

Let me just brief you on both the options first.

MBA is all about business part of anything. It will educate you the business part of any industry. It will be suitable if you want a career in pharmaceutical marketing. While studying MBA you will not study any pharma subject. You will be learning Finance, Marketing, Human Resources etc. While in M Pharm you'll learn technical subjects and whatever you learn will be as a specialization. If you are passionately curious as a student and you like to go deep in the matters or you like to do practicals and wish to join research or want to become a professor in future then M Pharm is the choice for you.

Now lets see the market for both these options. At present Pharma is considered as one of the saturated industries as far as recruitment is concerned. In today's market M Pharm graduates are struggling to get a suitable job. Freshers are not paid more than 10-12k a month. Your salary will reach to 20k only after at least 2 years of experience in Pharma Industry, be it production, packaging, QA, QC, whichever. So if you can compromise money for the sake of experience and the urge to feed your curiosity you should chose M Pharm.

On the other hand Pharma+MBA is a good combination to get a job. You can work as a medical representative, which is a sales job, includes field work and a lot of travelling in heat, cold and rainy weather. Being a sales job it includes meeting Doctors, Chemists, Distributors so it incorporates the art of managing people. It is a tough job but also rewarding, both in terms of remuneration and experience. It also develops your human skills. Your earnings would be around 20k in starting (salary+expenses, travelling and daily allowances+ incentives) and it can increase gradually as you change the companies.
After a couple of years' experience you can opt for a job in Product Management Team (PMT) which is a back office job and includes very little field work. Salaries are impressive and so is the job profile.

Let me tell you my story.
I completed my B Pharm in April, 2010. At that time I was interested in M Pharm, but unfortunately my GPAT score was not good enough to get me an admission into a government college and my family's financial condition wasn't good enough to get me an admission into a self finance college. So i decided to do a job and then prepare for next year's GPAT. I started job as a medical representative in a very good company. I was earning 20+k a month easily and was performing well. A year passed, the things were changed, I wasn't just a pharmacy graduate anymore, I was a B Pharm with one year experience. I was confused my heart was saying M pharm and mind was chanting MBA. I thought if I go for an M Pharm now, my experience of one year in Marketing field would not be of any use. So I chose to give both GPAT and GCET, the entrance exam for M Pharm and MBA respectively. I scored very well in GCET and managed to get admission in MBA department of a University, a government institute. I got my MBA in 2013 and now I'm working in a Pharma MNC at a very good salary.

So this is the scenario, rest you can choose for your self.