What is the ruling on gifts offered by pharmaceutical companies to doctors with the knowledge of the clinic owner, which take forms such as promotional gifts, or gratitude for prescribing medication when needed, or financial offers in exchange for prescribing a certain quantity, or gifts in exchange for studies conducted by the doctor on products he prescribes, or promotional invitations?

If the purpose of the gifts is to promote medicines without deception or fraud, and it is ensured that doctors are not favored in return, then there is no harm in them; because the default ruling for gifting is permissibility. However, if the purpose is unlawful promotion, then it is considered bribery, which is among the major sins. Paying a fee to a doctor for a specific study is a permissible act and there is no harm in it.