From Reuters:
Pfizer caps drug sales in bid to stop reimports
U.S. pharmaceuticals giant Pfizer has told its UK wholesalers it will only supply enough prescription medicines to meet domestic demand, in a bid to stop the reimportation of drugs back into the United States.

The move follows similar action by a number of international drug makers to restrict sales to Canada, where medicines are cheaper than in the U.S. There is a growing cross-border business in Canadian drugs being sold to U.S. residents.