Both Teva Pharmaceuticals and Pfizer have reported shortages of azithromycin, an antibiotic used in combination with hydroxychloroquine to treat COVID-19 patients, because of increased demand.
Azithromycin is often sold under the brand-name Z-Pak and treats various kinds of bacterial infections, including respiratory infections.
Teva said its azithromycin products will be on backorder for an unknown amount of time.
Pfizer, which sells azithromycin under the brand-name Zithromax, said it expects new shipments to come in May.
Providers have been using azithromycin in combination with hydroxychloroquine to treat severely ill COVID-19 patients, though it hasn't been proven to be effective in clinical trials.
The National Institutes of Health recently recommended against using azithromycin in combination with hydroxychloroquine due to potential side effects.