Doxycycline may reduce severity of COVID-19 symptoms in high-risk patients


4 case studies reveal doxycycline deserves more evaluation in these patients

doxycycline pills are wrapped in their foil packaging, on a table

Great interest lies in repurposing existing, approved drugs for the treatment of COVID-19. Tetracycline and its derivatives, including doxycycline, may offer a reasonable and safe treatment. Doxyclycline is commonly used to treat bacterial infections and skin conditions such as acne and rosacea with its antiviral and anti-inflammatory properties.

New case reports show a potential link between the use of doxycycline and the reduction of severity of COVID-19 symptoms.1 The reports support conducting more controlled clinical trials to evaluate the effects of doxycycline in this patient group.

Case 1

A 48-year-old Black woman with stage IV epidermal growth factor receptor (EGFR) mutated adenocarcinoma of lung was treated with osimertinib since November 2018 with response in all sites of disease. She was also given various medications for her condition, including loperamide and doxycycline for EGFR inhibitor-related diarrhea and rash, respectively.1

On April 6, 2020, she reported a fever of 101° F, anorexia, anosmia, and headache. She was also noted to have a mild cough, pulse 102, blood pressure 115/71 mm Hg, and oxygen saturation of 98% on room air.1

Laboratory tests revealed a level of 2.7 in white blood cells with lymphopenia.1 The results were similar to those of previous tests. Chest X-ray revealed stable right retrocardiac mid-opacities with no new focalization or effusion. The next day, her swab test returned positive for COVID-19.1

She was instructed to stop taking osimertinib and start taking doxycycline at 200 mg followed by 100 mg daily for 5 days. She noted that all of symptoms started improving immediately.

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Case 2

A 71-year-old male physician with a history of pulmonary sarcoidosis, treated with intermittent steroids, reported intermittent cough and diarrhea in April 2020. A nasopharyngeal swab test returned positive for COVID-19.1

He was started on doxycycline 100 mg twice a day, and his respiratory rate was continuously monitored at home.1

After experiencing a drop in oxygen saturation to 88% on day 6, he returned to the emergency department where his temperature was measured at 100.4° F.1 A chest X-ray showed evidence of chronic lower lung changes attributed to sarcoidosis.

He was prescribed doxycycline for 10 days and returned home. His fever resolved, and he returned to work in 3 weeks after retesting negative for COVID-19.1

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Case 3

A 40-year-old Asian woman with stage IV EGFR mutation in her lung adenocarcinoma was treated with osimertinib since June 2018. She also managed an EGFR-related rash with doxycycline.1

She presented to an urgent care center with 4 days of severe anosmia, mild cough, and mild dyspnea in July 2019. Nasopharyngeal swab testing returned positive for COVID-19.1

She continued taking osimertinib and doxycycline 100 mg twice daily for a week before symptoms improved. A follow-up nasopharyngeal swab test in May 2020 was for COVID-19.1

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Case 4

An 88-year-old white man with a variety of health conditions including sick sinus syndrome, cardiovascular disease, lacunar strokes, mild obstructive lung disease, and chronic indwelling bladder catheter, was admitted to a Veterans Affairs nursing home with a 102° F fever, severe dry cough, dyspnea, and weakness.1 A chest X-ray revealed bilateral diffuse infiltrates. Laboratory test results indicated mild hypoxia with O2 saturation of 89 to 92% and COVID-19.

His initial hospital treatment course included the use of ceftriaxone, azithromycin, and 2 liters of nasal prong O2, which led to a progression of his pulmonary symptomatology with decreasing O2 saturation requiring 4 liters of nasal prong O2 by day 3, with C-reactive protein (CRP) increase to 13.1

He was then treated with doxycycline 100 mg twice daily. Ceftriaxone and azithromycin were discontinued. His pulmonary course rapidly improved alongside decreasing CRP. His lung infiltrates resolved on chest X-ray after 14 days of doxycycline therapy, and he no longer required oxygen by day 8. He was discharged on day 28.1


Doxycycline is generally not recommended for the treatment of patients with COVID-19.1 However, these studies suggest some patients at high risk for morbidity and mortality from COVID-19 may experience mild or moderate clinical improvement if they are treated with this medication.


1. Yates PA, Newman SA, Oshry LJ, Glassman RH, Leone AM, Reichel E. Doxycycline treatment of high-risk COVID-19-positive patients with comorbid pulmonary disease. Ther Adv Respir Dis. 2020 Jan-Dec;14:1753466620951053. doi: \10.1177/1753466620951053

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