FAIRLESS HILLS, Pa. — Six drugmakers that manufacture generic hydroxychloroquine report the drug is in short supply, while three others reported in the last week that their product is available, according to the Food and Drug Administration’s drug shortages website.

The companies cite increased demand as the cause, with some stating they expect to next ship the drug at the end of May.

President Donald Trump said Monday he has been taking hydroxychloroquine and a zinc supplement daily “for about a week and a half now,” after two White House staffers tested positive for the coronavirus. Trump has spent months pushing hydroxychloroquine as a potential cure or preventive drug for COVID-19 against the cautionary advice of many of his administration’s top medical professionals.

One of the companies, Concordia Pharmaceuticals, also makes the brand-name version, called Paquenil. It says that drug is completely unavailable but is expected to be available again at the end of this month.