All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
In principle, a physician is trustworthy when it comes to diagnosing patients and prescribing suitable medications; therefore, he isn`t permitted to write a prescription that doesn`t suit the patient`s condition since doing so is an act of lying, cheating and betrayal of trust. Allah, The Exalted, Said (what means): " O ye who believe! Fear God and be with those who are true (in word and deed)." {At-Tawbah/119}. Also, Prophet Mohammad (PBUH) said: "He who deceives is not of us." {Muslim}.
In addition, the pharmacist who replaces the medication prescribed by the physician with other medications, or baby milk, and the like, upon patient`s request, is sinful because he has facilitated for the patient to violate the terms stipulated in the insurance contract between him and the insurance company.
Accordingly, it is forbidden for a pharmacist to exchange medications with other medications or pharmaceutical products, upon patient`s request, because the contract serves as the law for the contracting parties, and Allah, The Almighty, Says in this regard (what means): "but help ye not one another in sin and rancour: fear Allah. for Allah is strict in punishment." {Al-Maidah/2}.
In conclusion, it is incumbent upon the patient/insured to reject such violations, and advise both the physician and the pharmacist to fear Allah, Preserve people`s wealth, and not to violate their rights , instead of becoming a link in a chain of deception. Moreover, it is worth noting that it is forbidden for a Muslim to voluntarily conclude a health insurance contract with a commercial insurance company instead of cooperative insurance companies. And Allah Knows Best.