Business promotion

1. If you pay cash to doctors

Business Promtion A/c Dr
To Cash A/c

2. If in kind than

Business Promotion A/c Dr.
To Name of particular items

1. If you pay cash to doctors

Business Promtion A/c Dr 
To Cash A/c

2. If in kind than

Business Promotion A/c Dr.
To cash/Bank A/c

Yes it is taxable like other business.

Taxabilty

8% of your turnover (us 44AD)
or
if you want to show less profit than you need to maintain books of accounts financial statement for that particular financial year.
from this year if you show less than 8% you have to audit your books of account for next five year