a script for mirtazapine 45mg, the patient wanted the BRAND form " zispin or something for that", we refused to make the supply" as there is around 5 pound price difference" and apparently we are not a charity org

customer took his script to try it somewhere else.
what popped into my mind " did not ask the locum as he is a bit rude, saterday locum only lol" and i prefer to avoid any long conversation with him.
if we made the patient aware of the 5 pounds price difference, and he agree to pay for the difference, if it possible to make the supply or it depends on the company's SOP and regulations? i.e if we endorse the Rx for the generic product as it says on the script, get paid for the price difference, and supply the brand product.....?
what do you think p'cists?