The findings of a new study from UC San Francisco suggests that among non-hospitalised patients the antibiotic azithromycin was no more effective than a placebo in preventing symptoms of COVID-19. Despite widespread prescription of the antibiotic for the disease, it might increase the chance of hospitalisation.

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The study, which was conducted in collaboration with Stanford University, appeared in the Journal of the American Medical Association. "These findings do not support the routine use of azithromycin for outpatient SARS-CoV-2 infection," said lead author Catherine E. Oldenburg, ScD, MPH, an assistant professor with the UCSF Proctor Foundation. SARS-CoV-2 is the virus that causes COVID-19. Azithromycin, a broad-spectrum antibiotic, is widely prescribed as a treatment for COVID-19 in the United States and the rest of the world. "The hypothesis is that it has anti-inflammatory properties that may help prevent progression if treated early in the disease," said Oldenburg. "We did not find this to be the case."

The study included 263 participants who all tested positive for SARS-CoV-2 within seven days before entering the study. None were hospitalised at the time of enrollment. In a random selection process, 171 participants received a single, 1.2-gram oral dose of azithromycin and 92 received an identical placebo.

On day 14 of the study, 50 per cent of the participants remained symptom-free in both groups. By day 21, five of the participants who received azithromycin had been hospitalised with severe symptoms of COVID-19 and none of the placebo group had been hospitalised. The researchers concluded that treatment with a single dose of azithromycin compared to placebo did not result in greater likelihood of being symptom-free.

"Most of the trials done so far with azithromycin have focused on hospitalised patients with pretty severe disease," said Oldenburg. "Our paper is one of the first placebo-controlled studies showing no role for azithromycin in outpatients."