A stampede for an unproven “cure” for Covid-19 is clearing the pharmacy shelves of a medicine that is vital for up to 5 million people around the world suffering from lupus, as countries bow to populist pressure and abandon the trials that would show whether hydroxychloroquine works against coronavirus infection.

Both Italy and France have said doctors can now prescribe hydroxychloroquine – a less toxic version of the malaria drug chloroquine – even though there is no robust evidence to prove that it is effective against Covid-19.

Popular pressure for access to the drug has been ramped up by pronouncements from presidents Donald Trump in the US and Jair Bolsonaro in Brazil, both of whom have claimed it is a cure. An Australian businessman, the former politician Clive Palmer, has pledged to fund 1m doses “to ensure all Australians would have access to the drug as soon as possible”.

But the drug is already running out for people with lupus, a disorder of the immune system, who rely on it to stay well. Shortages are being reported from the UK to Thailand to France. India, which manufactures the raw ingredient, has banned all exports of the chemical to safeguard its own supplies and recommended all health workers to take the drug to protect themselves from the virus.

“We are incredibly concerned at the moment,” said Paul Howard of Lupus UK. “We started receiving inquiries from patients across the UK about a week ago. That’s been rapidly increasing – more and more people each day.”

For 90% of the more than 60,000 people in the UK with lupus, hydroxychloroquine is the mainstay of their treatment, preventing their immune system making too many antibodies, which can otherwise attack the body’s organs – mainly the kidneys and the skin, but also the heart, lungs and brain.

“Their local pharmacies don’t have any stocks available on the shelves,” said Howard. “They have no date for when they can expect stocks to arrive.”

There is no good alternative, he said. Other immunosuppressants have toxic side-effects and may put people at greater risk of Covid-19.

A nationalistic scramble is now on around the world to secure supplies of hydroxychloroquine in spite of the absence of rigorous evidence in the treatment of the coronavirus. One small trial in China produced good results, but was far from sufficient to show that it works.

In France, the government caved to pressure from a doctor who ran his own very small and rapid trial of the drug combined with an antibiotic in 26 people, using methodology that has been seriously criticised. Dr Didier Raoult, a professor of infectious diseases who works at La Timone hospital in Marseille, then declared in a video on YouTube that chloroquine was a cure for Covid-19 and should be used immediately.

Raoult walked out of the scientific advisory committee advising the government. A social media frenzy began, with allegations that the government was being influenced by the big pharmaceutical companies which wanted to block hydroxychloroquine because it was cheap, being out of patent. People queued outside Raoult’s hospital to be tested and get the drug, defying the lockdown. Finally, the French government gave way and decreed that hospitals could prescribe it for any Covid-19 patient. They can also give the anti-HIV medicine which is supposed to be in global trials for Covid-19, Kaletra, which is a combination of lopinavir and ritonavir.

Italy has followed suit. The government announced on Friday that chloroquine and hydroxychloroquine could be used to treat all Covid-19 patients and paid for entirely by the Italian national healthcare system. It would also pay for Kaletra.

The impact on the global trials to find out what really works is serious. Nick White, a professor of tropical medicine at Mahidol University in Thailand and at the University of Oxford, says the problem is enormous – not so much for malaria, where the drug is now less used, but for lupus patients and for hopes of finding out what works and sharing it globally.

“From Fauci [US government infectious diseases adviser, Dr Anthony Fauci] to the head of the World Health Organization, everyone says trials. It may be worse than nothing. We don’t know,” he said.

“The nationalistic shuttering down of export and import of drugs is serious. Drugs are manufactured in relatively small numbers of places and have to be moved to other places.

“The indirect harm could be worse than the impact of Covid-19,” he said. “it is not just the drugs that might work. It is all drugs. Italy, for instance, is a major source of drugs for the NHS. This is a very big area. It is getting bigger by the minute. And the opportunity to answer the sensible question – do these things work, yes or no? – is narrowing as countries become more nationalistic in terms of hoarding drugs.”