Azithromycin and doxycycline are two commonly used antibiotics investigated as separate treatments in the trial. Both drugs are being used by some doctors in the hope of treating COVID-19 in the early stages of the illness.
After reviewing interim analyses of both the azithromycin and doxycycline arms of the PRINCIPLE trial, the independent Trial Steering Committee advised the trial investigators, who concluded that there is no beneficial effect in patients aged over 50 who are treated with either antibiotic at home in the early stages of COVID-19. This is because interim data analyses show that neither treatment reduces the time taken for people to first report that they feel recovered sufficiently to achieve meaningful clinical benefit. The PRINCIPLE trial did not look at the effects of these drugs in patients who were already admitted to hospital with COVID-19.
No further people are therefore being randomised to receive azithromycin or doxycycline in the PRINCIPLE trial.