Mexico, drug purchases

Mesquite gum is collected by the natives in the southwestern United States and northern Mexico. It is carried by most drug stores in this region and may be purchased from the Martin Drug Company of Tucson, Arizona. 

The male client tells the clinic nurse that he purchased over-the-counter Tylenol in Mexico for back pain that worked very well and now he has purchased Tylenol at the local drug store, but now the medication does not work. Which statement would be... 

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