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Can pharmacists legally change a doctor's prescription without the patient's permission?
Answer:
When a doctor writes a prescription, he usually can sign it either "substitution permitted" or "dispense as written". The usual "substitution" is dispensing a generic drug in place of a brand-name drug- this is the SAME chemical compound, approved by the FDA as being absorbed exactly like the brand-name drug. When a doctor writes a prescription for Viagra (active ingredient sildenafil citrate) and signs it as "substitution permitted", the pharmacist can then dispense generic sildenafil citrate in the same dosage, which saves the customer a lot of money. It's the same active ingredient in the same purity and concentration absorbed in the same way with the identical effects-only it's much much cheaper. The pharmacist can't be creative, change the dose or decide that he'll give you some different compound like Cialis (a different compound) to treat your erectile woes when making a substitution.
So no, the pharmacist doesn't have the liberty to dispense a different compound to you. He might give you the same thing in a generic form and not ask for your permission (since it's your doctor that's making the calls here and said the pharmacist could substitute, not you). There's absolutely no reason not to choose generic drugs whenever they are available. It's not like buying Coca-Cola and the store brand "Cola Product" knockoff where both are pretty similar but the Coca-Cola definitely tastes better- Pfizer's Viagra and a generic are both FDA approved as being identical in potency and doing the same thig.
http://wiki.answers.com/Q/Can_pharmacists_legally_change_a_doctor%27s_prescription_without_the_patient%27s_permission 
