(Bloomberg) -- Nearly half the supply of hydroxychloroquine to the U.S. comes from makers in India, a flow that has now been abruptly stanched after the Asian nation banned exports of all forms of the malaria drug touted by President Donald Trump as a “game changer” for treating the coronavirus.

According to data compiled by Bloomberg Intelligence, 47% of the U.S. supply of the drug last year came from India makers. Only a handful of suppliers in the top 10 are non-Indian, such as Actavis, now a subsidiary of Israeli generics giant Teva Pharmaceutical Industries Ltd. It’s likely that some of their production facilities are nevertheless located in India, the biggest maker of generic drugs in the world.

India’s export ban on the drug is aimed at ensuring it has enough supply for domestic use after the American president’s endorsement sparked global stockpiling of the medication. As the coronavirus pandemic widens globally, countries competing for supplies have enacted export bans or restrictions on goods from rice in Vietnam to face masks in Germany.

While Trump said that the U.S. has secured 29 million choloroquine or hydroxychloroquine pills for its medical stockpile and American drugmakers like Mylan NV have re-started production of the tablets to meet U.S. needs, the India ban will likely push prices of the medication up in the short-term, while limiting available supply in the long-term.

The active chemical compound needed to make the drug is also mainly supplied through Indian channels and is now banned for export too, potentially complicating efforts like Mylan’s.

There’s no conclusive scientific evidence that hydroxychloroquine can treat the infection from the novel coronavirus, and it hasn’t been approved by the Food and Drug Administration in the U.S. for Covid-19.

India’s April 4 move was an expansion of an announcement last month which banned overseas shipments of the drug except for those to meet prior commitments and for humanitarian grounds. There are now no exceptions to the export ban.

The top U.S. supplier of hydroxychloroquine, Zydus Pharmaceuticals Inc., is a subsidiary of Ahmedabad, India-based Cadila Healthcare Ltd. It sold over 167 million units of the anti-malarial in 2019, according to Bloomberg data, and has supplied 28 million integrated units to retail and institutional channels in the U.S. so far this year.

Prior to the ban, Cadila said it was planning to ramp up production of hydroxychloroquine tenfold to meet surging global demand.