Claire Fuller says there's no way of knowing if her recovery was aided by the drug she was given.
The 56-year-old is one of the first Covid-19 patients to take part in trials for possible treatments.
She was treated with the anti-malaria drug hydroxychloroquine after she was taken into Royal Devon and Exeter Hospital at the end of March.
Recovery, which is being co-ordinated at Oxford University, signed up 1,000 patients from 132 different hospitals in its first 15 days and, according to reports, now has almost 3,000 volunteers.
Ms Fuller was one of the first patients to take part in the Exeter arm of the Randomised Evaluation of Covid-19 Therapy trial, which is the largest randomised clinical trial of potential coronavirus treatments in the world.
Hydroxychloroquine has been hailed as a possible breakthrough in the fight against coronavirus by US President Donald Trump, and is one of a series of existing drugs which are being tested across the UK in the fastest growing trial in UK medical history.
Recovery is trialling three other drugs as well as hydroxychloroquine.
Ms Fuller was taken to hospital when her breathing deteriorated ten days after developing a dry cough.
"It was really scary how it just suddenly turned," she said.
The mother of two said: "They asked me if I'd take part in the study when I was still in A&E.
"It didn't take long for me to agree. The more people they get, the better."
Ms Fuller said she was given a loading dose of eight tablets of hydroxychloroquine to start with and then, after another heavy loading dose, it was two tablets for the remaining four days she was on the Covid-19 ward.
She said that she has no idea whether some of the symptoms she experienced, and her recovery, were due to the infection or were side-effects of the drug.
She said: "I was getting what was like a flushing feeling - a hot, sharp, tingling going through my lungs.
"I don't know whether this was me responding to the drug or the virus.
"Until they get more people through the trial they will not know. That's the point of the study."
Ms Fuller said the only other possible side-effect she suffered was some gastric issues. But she thinks this may have been virus rather than drug-related as another patient in her four-bed Covid-19 bay had the same and was not on the trial.
She said: "I think, though, that if I'd had a bad reaction to the drug, that would have been evidenced."
Ms Fuller said the doctors, like their patients, are not sure which presentations are down to the virus or the drugs.
"They'll only know that when more and more people take part," she said.
"The doctors were saying that all the patients coming in with Covid-19 are coming in with a slightly different presentation. They are literally learning with each one being admitted, poor guys."
Ms Fuller, who works as a global manager for a veterinary company, is now recovering at home after she was discharged a week ago.
She says she simply does not know if her recovery was aided or hastened by the hydroxychloroquine, but encouraged anyone who has the chance to sign up for the trial.
Oxford's Recovery trial, which is hospital-based, is one of three key national trials.
The others are Principle, which is focused on higher risk patients in primary care, and Remap-Cap, which is concentrated on critically ill patients with community-acquired pneumonia.