The company has initiated the product launch in Denmark, Czech Republic, Slovakia, Portugal and Poland, where Zoviduo/Zovirax Duo is approved for OTC sales.
GSK will launch the product in the remaining markets in Europe as the respective regulatory authorities grant approval for OTC sales, the company said.
Under the agreement signed by the companies in June 2010, GSK is responsible for funding commercial development of Xerclear, including marketing approval for OTC sales in all territories.
GSK will pay Medivir up to double-digit royalties on sales for the exclusive rights.
The remaining Euro1.9m in milestones, according to the agreement, will be due for payment at the time of future OTC product launches in certain pre-defined countries.
Medivir CEO Maris Hartmanis said few companies of their size have experienced the launch of a product, developed in-house, that is now being introduced in Europe.