Is working in a pharmacy that sells the most profitable medications to customers instead of others, sometimes changing the customer's mind to take the more profitable product, permissible or forbidden?

"Religion is counsel for Allah, for His Book, for His Messenger, for the leaders of the Muslims, and for their common folk." Part of counseling the common folk of Muslims is guiding them to what benefits them in the hereafter and in this world, refraining from harming them, teaching them what they are ignorant of concerning their religion, assisting them with words and deeds, concealing their faults, repelling harm and bringing about benefits, and enjoining good and forbidding evil with gentleness and sincerity.

If a customer specifies a medicine, it is not permissible to deny it to him through falsehood or deception, as this contradicts counseling and falls under prohibited fraud. It is permissible to change his mind truthfully, without fraud or deception. If the customer does not specify a medicine, there is no harm for the pharmacist in selling the medicine that is profitable for him, provided it is suitable for his need.