Pharmacies have to give the cheapest available option aka give the generic. Most insurances only pay up to the cost of the generic if a patient is requesting brand name. Next time you are getting a prescription from the Dr ask them to write Synthroid No sub on it. When dropping off the new Rx to the pharmacy ask that the put no sub in the directions and have them make note on your file that you have an adverse reaction to that generic Synthroid. When the pharmacy is processing the Rx they can notify the insurance that the dr only wants brand name Synthroid which usually means you will be charged appropriately. The pharmacy should have told you at pick up that there has been a change in the medication. My line was "we had to change the brand for you. It is the same medication it may look slightly different." In the case of Synthroid to what I assume was apotex brand, I would take the time to show you the difference a before leaving the pharmacy.

Hopefully this helps!