Praise be to Allah.
There is nothing wrong with internship doctors attending medical conferences affiliated with pharmaceutical companies or in which pharmaceutical companies participate, because there are no shar‘i reservations concerning that, such as enticing the doctor to prescribe the company’s drugs, even if some other drug is more beneficial to the patient, or giving gifts to workers, if the doctor is an employee of a hospital or the like. These reservations are not applicable in the case of the internship doctor who has not graduated yet.
There is nothing wrong with eating the food that is served at these conferences.
Dr ‘Abd ar-Rahman ibn Ahmad al-Jar‘i said in his paper Hadaya ash-Sharikat al-‘Amilah fi’l-Majal at-Tibbi (Gifts given by companies working in the medical field):
Scientific trips and attending conferences:
Some companies sponsor these trips and conferences. If this sponsorship is accompanied by a stipulation that the doctors should prescribe the medicines or equipment produced by these companies, then it is not permissible to attend, because the doctor’s role is to do what is in the patient’s best interests, and to give him the appropriate treatment, not to serve the interests of these companies. Moreover, disallowing that is for the purpose of warding off harm that is expected to result from restricting treatment to the company’s medicines, because that is detrimental to the patients, as is quite obvious, because other companies may have medicines that are more beneficial and cheaper.
But if this sponsorship comes with no strings attached, then I think that the ruling depends on the motive behind the sponsorship. If the motive is to support scientific research, and that can be clearly seen – for example, if these companies have a special budget to support scientific research, and has nothing to do with promoting or marketing any of the company’s products – then I do not see anything wrong with accepting this sponsorship for trips and conferences, because the basic principle is that it is permissible to accept gifts."(Buhuth Mu’tamar al-Fiqh al-Islami ath-Thani bi Jami‘at al-Imam Muhammad ibn Sa‘ud al-Islamiyyah: Qadaya Tibbiyyah Mu‘asirah, p. 4166).
And Allah knows best.