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1520 P J M H S Vol. 15, NO. 4, APRIL 2021
Effectiveness and Safety Doxycycline in treating COVID-19 Positive
Patients: A pilot clinical study
ZOHREH AKHOUNDI MEYBODI1, SEYED RUHOLLAH MOUSAVINASAB2, MOHAMMAD BAGHER OWLIA3, SINA OWLIA4
1MD, Infectionlogist fellowship Prevention and Control of Nosocomial Infection, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
Email: email@example.com. ORCID ID: ORCID ID: https://orcid.org/0000-0002-8409-4192.
2PharmD, Resident of Clinical Pharmacy, Department of Clinical Pharmacy, School of Pharmacy, Shiraz University of Medical Sciences,
Shiraz, Iran. Email: firstname.lastname@example.org. ORCID ID: https://orcid.org/0000-0002-8447-0661.
3MD, Professor of Medicine, Department of Internal Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Email:
email@example.com. ORCID ID: https://orcid.org/0000-0001-8062-6430.
4MD, Research Assistant, Department of Internal Medicine, Shahid Sadoughi Hospital, Shahid Sadoughi University of Medical Sciences,
Yazd, Iran. Email: firstname.lastname@example.org. ORCID ID: https://orcid.org/0000-0002-0982-8256.
Corresponding author: PharmD, Resident of Clinical Pharmacy, Department of Clinical Pharmacy, School of Pharmacy, Shiraz University of
Medical Sciences, Shiraz, Iran. Postal code: 7146864685, ORCID ID: https://orcid.org/0000-0002-8447-0661, Tel: +987132424128, Fax
number: +987132424126, Email: email@example.com
Objective: Given the high morbidity and mortality caused by Coronavirus Disease 2019 (COVID-19), scientific
research is necessary to achieve a proper treatment regimen. Since doxycycline is effective in reducing
inflammatory factors, including IL-6 and TNF-alpha that play an essential role in initiating cytokine storms and
probably causing death in patients with COVID-19, its use is associated with low side effects and can be used
orally; the, present study was attempted to evaluate the efficacy of doxycycline in the treatment of inpatients and
outpatients with COVID-19.
Methods: This descriptive and prospective study was performed on inpatients and outpatients who were
diagnosed with COVID-19 based on polymerase chain reaction (PCR) test from nasopharyngeal secretions or
computerized tomography scan (CT scan). Patients who met the inclusion criteria received doxycycline at a dose
of 100 mg every 12 hours for seven days and then were evaluated on the baseline day. On days 3, 7, and 14
after admission for cough, shortness of breath, temperature, and oxygen saturation.
Finding: Out of 21 patients, 11 patients were male, and ten patients were female. Cough, shortness of breath,
temperature, and O2 sat improved in both outpatients and inpatients compared to baseline. In general, the results
showed that doxycycline was more effective in improving cough, SOB, temperature, and O2 sat in outpatients
Conclusion: The results of this study show that doxycycline with the dose and duration prescribed in our study
could play a useful role in treating patients with COVID-19.
Keyword: Doxycycline, COVID-19, Outpatients, Inpatients, Treatment
The new coronavirus has emerged since late 2019 and
spread rapidly worldwide, turning to a pandemic. Medical
scientists and researchers are trying to find effective drugs
to treat this disease . Coronaviruses are named positive-
sense RNA viruses because of having crown-like spikes on
their surfaces. Coronaviruses are a large family of viruses
belonging to Nidovirales, family Coronaviridae [2, 3].
January 2nd; September 14; September 28, 2020, 41
patients were diagnosed with Coronavirus Disease 2019
(COVID-19) COVID-19 infection based on laboratory tests.
Less than half of them had underlying diseases, such as
diabetes, hypertension, and cardiovascular disease . In
doing so, several measures have been taken to produce
and distribute the vaccines . In patients with COVID-19,
the number of leukocytes in the respiratory system is
abnormally high. The primary pathogenesis of COVID-19 is
severe pneumonia, RNAaemia, the incidence of ground-
glass opacities, and acute heart injury. Significantly high
blood levels of cytokines and chemokines are seen in
patients with COVID-19, including IL1-β, IL1RA, IL7, IL8,
IL9, IL10, basic FGF2, GCSF, GMCSF, IFNγ IP10, MCP1,
MIP1α, MIP1β, PDGFB, TNFα, and VEGFA. In some
severe cases admitted to the intensive care unit, an
increase in mortality with high levels of proinflammatory
cytokines, including IL2, IL7, IL10, GCSF, IP10, MCP1,
MIP1α, and TNFα, has been observed . Tetracyclines
are lipophilic compounds that have good tissue penetration;
hence, there is a good concentration of this drug in the
skin, nails, scalp, conjunctiva, tears, milk, saliva, and
intracellular fluid . They are broad-spectrum
bacteriostatic compounds and have activity against gram-
positive and gram-negative bacteria, intracellular
organisms, atypical organisms (e.g., Chlamydia and
Mycoplasma Virginia), and protozoan parasites [7, 8]. The
mechanism of action of doxycycline is to inhibit bacterial
protein synthesis through the irreversible binding of the 30S
and possibly 50S ribosomes and alterations in the
cytoplasmic membrane. [6-8]. Oral doxycycline is almost
completely absorbed, and its plasma concentration is
reduced by 20% when consumed with high-fat foods or
milk. It is well distributed in most body fluids, including
pleural, synovial, and bronchial secretions. It's binding to
proteins is more than 90%. One of the advantages of this
drug is that no dose adjustment is required in patients with
On the other hand, telemedicine has been addressed
as one of the solutions for reduction of disparities in
accessing the healthcare service during the Covid-19
pandemic, which is shown to have has decreased racial
Zohreh Akhoundi Meybodi, Seyed Ruhollah Mousavinasab, Mohammad Bagher Owlia et al
P J M H S Vol. 15, NO. 4, APRIL 2021 1521
disparities and prepared higher accessibility for older
The bioavailability of this drug decline at high pH
conditions, such as gastrectomy, gastric bypass surgery, or
achlorhydric disorder. The half-life of this drug is 18 to 22
hours. It is contraindicated in children less than eight years
of age, during pregnancy, and lactation [10, 11]. The anti-
inflammatory mechanism of doxycycline is inhibition of
bacterial products, including reducing the production of
chemotactic neutrophil cytokines, which stimulates
inflammatory processes. Doxycycline in vitro and dermal
studies inhibit leukocyte migration by intracellular chelating
calcium at the onset of the inflammatory process.
Tetracyclines can also suppress alpha-amylases,
phospholipase A2, TNF (α), and interleukin1beta (IL-1β).
Doxycycline can reduce the levels of inflammatory
cytokines in neonatal rats, such as TNFα, IL-1β, and IL-6
[9, 12-14]. However, doxycycline is more effective than
tetracycline in reducing pro-inflammatory cytokines [15, 16].
In this study, we assessed the effect of doxycycline in both
outpatients and inpatients with COVID-19. Patients were
evaluated on the baseline day and days 3, 7, and 14 after
admission for cough, shortness of breath (SOB),
temperature, and O2 sat.
Setting and population: This prospective, open-label, and
a non-randomized pilot study were conducted on both
inpatients and outpatients with COVID-19 who were
referred to Baghaeipour Clinic, Shahid Sadoughi Hospital,
Yazd, Iran, from January 2nd; September 14;
September28. The patients were diagnosed with COVID-19
based on polymerase chain reaction (PCR) test or
computerized tomography scan (CT) manifestations. The
patients referred to Baghaei Pour Clinic, Shahid Sadoughi
Hospital, Yazd, Iran, who indicated inpatients and
outpatient treatment, were evaluated for inclusion and
exclusion criteria. On initial examination, patients were
evaluated for cough, SOB, temperature, and O2 sat.
Cough and SOB were scored as follows: zero: no cough or
SOB, 1: mild cough or SOB, 2: moderate cough or SOB, 3:
severe cough or SOB, and 4: very severe cough or SOB.
After the patients were evaluated for inclusion criteria,
signing the informed consent form by patients, 21 patients
entered the study. This is a pilot study and the presented
results are part of the products. The full results will be
published in another article.
Exclusion and inclusion criteria: Patients were included
in the study if they met the following criteria: minimum age
18 and maximum age 80 years, willingness to participate in
the research and signing the informed consent form, not
take doxycycline during the past 14 days, being suspected
with COVID-19 based on clinical signs and CT scan
manifestations, and being a candidate for inpatient and
Intervention: Patients who met the inclusion criteria
received doxycycline at a dose of 100 mg every 12 hours
for seven days along with standard treatment.
Data gathering & Measurements: Demographic, clinical,
and therapeutic information was obtained by writing down
the desired information from the patients' files and
designing a questionnaire. This questionnaire contains
information about age, sex, underlying condition, cough,
temperature, SOB, temperature, and percentage of O2 sat.
Patients were evaluated on the baseline day and days
3, 7, and 14 after admission for cough, dyspnea (SOB),
temperature and O2 sat.
Ethical approval: This study was initiated after obtaining
the Ethics ID (IR.SSU.MEDICINE.REC.1399.140) by the
Ethics Committee of Biomedical Research, School of
Medicine, Shahid Sadoughi University of Medical Science,
Yazd, Iran. This study was approved in the Iranian Registry
of Clinical Trials (IRCT20191211045691N2).
Statistical analysis: The data were coded and entered
into SPSS version 20. We used Friedman and Wilcoxon
tests to compare qualitative variables. P values less than 0.
05 were considered to be statistically significant.
Out of 21 cases, nine patients were inpatients (42.86%),
and 12 were outpatients (57.14%). Men made up 52.38%,
and women 47.62% of the patients. Three patients had an
underlying disease, including diabetes, hypertension, and
lymphoma. Only two patients were admitted to the ICU,
and no deaths occurred in this study. Cough and SOB were
scored as follows: zero: no cough or SOB, 1: mild cough or
Table 1: Comparison of cough on days 3, 7, and 14 of compared to the baseline day in inpatients and outpatients
*Cough was scored
zero: no, 1: mild, 2: moderate, 3: severe and 4; very severe cough.
** The Friedman test was used for the statistical differences.
Effectiveness and Safety Doxycycline in treating COVID-19 Positive Patients: A pilot clinical study
1522 P J M H S Vol. 15, NO. 4, APRIL 2021
Table 2 Comparison of SOB on days 3, 7, and 14 compared to the baseline day in inpatients and outpatients
*SOB was scored
zero: no, 1: mild, 2: moderate, 3: severe, and 4; very severe SOB.
** The Wilcoxon test was used for the statistical differences.
Table 3 Comparison of temperature on days 3, 7, and 14 compared to the baseline day in inpatients and
* The Wilcoxon test was used to for the statistical differences.
Table 4 Comparison of O2 sat on days 3, 7, and 14 compared to the baseline day in inpatients and outpatients
The Wilcoxon test was used to find any statistical differences.
Fig. 1 A summary of the anti-inflammatory activities induced by doxycycline
(36 – 38.5)
(37 – 38)
O2 sat (%)
Zohreh Akhoundi Meybodi, Seyed Ruhollah Mousavinasab, Mohammad Bagher Owlia et al
P J M H S Vol. 15, NO. 4, APRIL 2021 1523
SOB, 2: moderate cough or SOB, 3: severe cough or SOB,
and 4: very severe cough or SOB. In both groups, cough
improved compared to baseline. This improvement was
significant on days 7 and 14 (p<0.05), but on the fourteenth
day, 75% of outpatients and 33.3 % of inpatients had a
zero score (Table 1). SOB in both inpatients and
outpatients improved significantly on days 7 and 14
(p<0.05). In outpatients, on days 7 and 14, moderate,
severe, or very severe form of SOB was not observed;
however, in inpatients on the seventh day, only a very
severe form of SOB was not observed. On the fourteenth
day, a severe and very severe SOB form was not observed
in inpatients (Table 2). In both inpatients and outpatients,
body temperature improved significantly from day three
onwards, but this change was greater in inpatients (Table
3). Inpatients' O2 sat improved significantly on day 14
compared to baseline (p<0.012). However, in outpatients,
O2 sat improved significantly on days 3, 7, and 14 (p<0.37,
P<0.37, and P<0.012, respectively) (Table 4).
This study aimed to evaluate the efficacy of doxycycline in
treating COVID-19 patients. Patients were assessed for
cough, shortness of breath, temperature, and O2 sat on
baseline day and 3, 7, and 14 days. They were definitively
diagnosed with COVID-19 based on a CT scan and PCR
test. According to the results, doxycycline was effective in
treating both inpatients and outpatients, and no patients
was excluded from the study due to side effects. Alam et
al.,  evaluated the impact of the combination of
doxycycline and ivermectin on 100 high-risk COVID-19
patients. The symptoms of all patients improved within 72
hours, and no significant side effects were observed. They
concluded that the combination of ivermectin and
doxycycline was very effective in viral clearance in mild and
moderately sick COVID-19 patients. Although in our study
doxycycline was given to patients for a shorter period, the
patients' symptoms resolved within 72 hours.
Doxycycline is a bacteriostatic antibiotic, and inhibit
bacterial protein synthesis by reversibly binding to the 30S
ribosomal subunit and preventing the association of
aminoacyl-tRNA with the bacterial ribosome. A summary of
the anti-inflammatory activities of doxycycline are shown in
Figure1. As shown in this figure, doxycycline inhibits IL-6
and TNF-alpha, which play an essential role in disease and
mortality from COVID-19 . Doxycycline in doses of 100
and 200 mg usually has no significant side effects and is
well tolerated by patients. The most crucial side effects of
this drug are gastrointestinal side effects, such as diarrhea,
nausea, vomiting, and esophagitis. The risk of esophagitis
can be reduced using enteric-coated products and
monohydrates formulation or consumption of medicine with
enough water and be upright for 30 minutes after
administration . In our study, only gastrointestinal side
effects were observed, and doxycycline was safe and
tolerable by patients.
It seems that doxycycline at the dose and duration
prescribed in our study can be useful in the treatment of
patients with COVID-19 given that improved patients’
cough, SOB, temperature, and O2 sat during the research,
and safe and tolerable for patients. Also, this drug is
covered by insurance, can be used orally, and does not
have hepatic metabolism; therefore, this drug can be
prescribed without dose adjustment in hepatic impairment.
Abbreviations: COVID-19: Coronavirus Disease 2019;
PCR: polymerase chain reaction test; CT: Computerized
tomography scan; O2 sat: oxygen saturation; ICU:
intensive care unit; IL-1β: interleukin1beta; SOB: Shortness
Acknowledgments: We thank all those who helped us
with this project.
Authors’ contributions: Study design and protocol
development: MBO, SO, ZAM and SRM. Patients'
recruitment and follow up: ZA. Data analysis: SRMN.
Manuscript preparation and submission: MBO, ZAM, and
SRMN. All authors will read and approved the final
manuscript before submission.
Funding: No organization or agency paid for this study.
Availability of data and materials: We, the authors,
apologize for providing patient information to this journal
because we did not consent to the publication of their
Ethics approval and consent to participate: This study
was initiated after obtaining the Ethics ID
(IR.SSU.MEDICINE.REC.1399.140) by the Ethics
Committee of Biomedical Research, School of Medicine,
Shahid Sadoughi University of Medical Science, Yazd, Iran.
This study was approved in the Iranian Registry of Clinical
Consent for publication: Not Applicable.
Competing interests: None declared.
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