A pious Muslim has always to be cautious about the sources of his earnings. Unlawful earnings invoke the wrath of Almighty Allah and endangers the Muslim’s life in the Hereafter as he will be held accountable for such gains. As reported in the sound hadith, Allah is good and only accepts good things.
In his answer to the question, Dr. Monzer Kahf, Scholar in Islamic Economics & Financial Expert, stated,
“These gifts given to doctors by Pharmaceutical companies as described are permissible to accept as long as the accepting doctor knows himself/herself for certainly that accepting such gifts does not induce him/her to prescribe this medicine. Normally, there are no conditions attached to them.”