Global pharmaceutical shares are slumping Monday after President Donald Trump said he is looking to slash the price of prescription drugs in the U.S. by as much as 80%.

US President Donald Trump has signed an executive order that aims to reduce high prescription drug prices – but its details and long-term effects are far from clear. Citing figures that patients in other countries pay much less than Americans for pharmaceuticals, Trump said he would order drug companies to reduce their prices inside the US.

US drug prices are up to five times higher than in other developed nations. Trump's order requires US drug prices to align with the lowest prices paid in those countries. He framed the move as a long-overdue correction to "decades of unfair pricing," claiming that US consumers have been subsidizing drug costs globally.