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c19early.org COVID-19 treatment researchAntihistamine H1RAsH1RAs (more..)
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Summary of COVID-19 antihistamine H1RA studies

Studies   Meta Analysis   Hide extended summaries

101 patient chlorpheniramine early treatment RCT: 61% improved recovery (p=0.0002) and 74% lower PASC (p=0.001).
RCT and retrospective study of chlorpheniramine nasal spray for COVID-19. The RCT included 101 outpatients showing significantly faster recovery with treatment. The retrospective study results are listed separately [Valerio-Pascua]. Long COVID results are from [Valerio-Pascua].

Oct 2022, Research Square, https://www.researchsquare.com/article/rs-2167465/v1, https://c19p.org/valeriopascua3

45 patient chlorpheniramine early treatment RCT: 87% lower hospitalization (p=0.08).
Small RCT showing significantly improved recovery with intranasal chlorpheniramine maleate. Authors also perform an In Vitro study showing efficacy with a highly differentiated three-dimensional model of normal, human-derived tracheal/bronchial epithelial cells.

Dec 2022, Medical Research Archives, https://esmed.org/MRA/index.php/mra/article/view/2752, https://c19p.org/sanchezgonzalez2

loratadine prophylaxis PSM study: 80% lower mortality (p=0.05).
PSM retrospective 3,712 hospitalized patients in Spain, showing lower mortality with existing use of loratadine.

Jan 2022, Pharmaceuticals, https://www.mdpi.com/1424-8247/15/1/78, https://c19p.org/monserratvillatoroh1

26,508 patient antihistamine H1RA prophylaxis study: 43% lower mortality (p<0.0001).
Retrospective 26,508 consecutive COVID+ veterans in the USA, showing lower mortality with multiple treatments including antihistamines. Treatment was defined as drugs administered ≥50% of the time within 2 weeks post-COVID+, and may be a continuation of prophylactic treatment. Further reduction in mortality was seen with combinations of treatments.

Jun 2022, J. General Internal Medicine, https://link.springer.com/10.1007/s11606-022-07701-3, https://c19p.org/hunth1

15,103 patient hydroxyzine prophylaxis study: 46% lower mortality (p=0.02).
Retrospective 15,103 hospitalized COVID-19 patients in France showing lower mortality with hydroxyzine use.

Dec 2021, J. Clinical Medicine, https://www.mdpi.com/2077-0383/10/24/5891, https://c19p.org/sanchezrico2

15,968 patient antihistamine H1RA prophylaxis study: 40% lower mortality (p=0.003).
Retrospective 15,968 COVID-19 hospitalized patients in Spain, showing lower mortality with antihistamine H1RAs, without statistical significance. Since only hospitalized patients are included, results do not reflect different probabilities of hospitalization across treatments.

Aug 2022, Virology J., https://virologyj.biomedcentral.com/articles/10.1186/s12985-023-02195-9, https://c19p.org/loucera3h1

antihistamine H1RA prophylaxis study: 34% fewer cases (p<0.0001).
Retrospective 219,000 patients showing lower risk of COVID-19 with antihistamine H1RA use. In Vitro study showing these drugs exhibit direct antiviral activity against SARS-CoV-2. Molecular docking suggests hydroxyzine and azelastine may exert antiviral effects by binding ACE2 and the sigma-1 receptor.

Jan 2021, Biochemical and Biophysical Research Communications, https://www.sciencedirect.com/science/article/pii/S0006291X20321409, https://c19p.org/reznikov

660 patient chlorpheniramine early treatment study: 54% faster recovery (p<0.0001).
RCT and retrospective study of chlorpheniramine nasal spray for COVID-19. The retrospective study included 660 outpatients showing fewer days with general COVID-19 symptoms, cough, anosmia, and ageusia compared to standard of care alone. The RCT results are listed separately [Valerio-Pascua].

Oct 2022, Research Square, https://www.researchsquare.com/article/rs-2167465/v1, https://c19p.org/valeriopascua3b

7,345 patient hydroxyzine prophylaxis study: 58% lower mortality (p=0.001).
Retrospective 7,345 hospitalized COVID-19 patients in France showing lower mortality with hydroxyzine use, with a significant dose-response relationship. Hydroxyzine was also associated with a faster decrease in inflammatory markers.

Oct 2020, medRxiv, https://www.medrxiv.org/content/10.1101/2020.10.23.20154302, https://c19p.org/hoertel6

34,936 patient antihistamine H1RA prophylaxis study: 61% fewer cases (p=0.1).
Retrospective 34,936 hypertensive outpatients in Spain showing no significant difference in COVID-19 cases with PPIs and antihistamine H1RAs.

Jul 2020, The J. Clinical Hypertension, https://onlinelibrary.wiley.com/doi/10.1111/jch.13948, https://c19p.org/vilacorcoles2h1

79,083 patient antihistamine H1RA prophylaxis study: 53% fewer cases (p=0.05).
Retrospective 79,083 adults aged ≥50 years in Spain showing lower with of PCR-confirmed COVID-19 with antihistamine use, close to statistical significance.

Dec 2020, BMJ Open, https://bmjopen.bmj.com/lookup/doi/10.1136/bmjopen-2020-041577, https://c19p.org/vilacorcoles

27 patient antihistamine H1RA long COVID study: 29% lower PASC (p=0.1).
Retrospective 14 patients with long-COVID symptoms attributed to mast cell activation treated with H1 and H2 antihistamines compared to 13 control patients, showing significant improvements in several symptoms in the treatment group compared to controls after 20 days. 29% of treated patients had complete resolution of long-COVID symptoms, compared with none in the control group.

Jul 2023, Frontiers in Cardiovascular Medicine, https://www.frontiersin.org/articles/10.3389/fcvm.2023.1202696/full, https://c19p.org/salvucci

176 patient antihistamine H1RA late treatment PSM study: 25% lower mortality (p=0.4).
PSM retrospective TriNetX database analysis of 1,379 severe COVID-19 patients requiring respiratory support, showing lower mortality with H1RAs+H2RAs versus famotidine alone, without statistical significance.

Mar 2021, Signal Transduction and Targeted Therapy, https://www.nature.com/articles/s41392-021-00689-y, https://c19p.org/murah1

5,772 patient antihistamine H1RA prophylaxis study: 7% higher mortality (p=0.5).
Retrospective 72,105 COVID+ hospitalized patients in France, showing no significant difference in mortality with antihistamine H1RAs desloratadine and hydroxyzine.

Aug 2023, Pharmaceuticals, https://www.mdpi.com/1424-8247/16/8/1107, https://c19p.org/hoertel5h1

36,160 patient antihistamine H1RA prophylaxis study: 30% higher severe cases (p=0.0004).
Retrospective 4,251 severe COVID-19 cases and 36,738 matched controls in Scotland showing increased risk of severe COVID-19 with PPI use and antihistamine H1RA use. Adjusted results are only provided for the patients not in care homes (2,357 cases and 33,803 controls).

Feb 2021, BMC Medicine, https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-021-01907-8, https://c19p.org/mckeigueh1
Please send us corrections, updates, or comments. c19early involves the extraction of 100,000+ datapoints from thousands of papers. Community updates help ensure high accuracy. Treatments and other interventions are complementary. All practical, effective, and safe means should be used based on risk/benefit analysis. No treatment or intervention is 100% available and effective for all current and future variants. We do not provide medical advice. Before taking any medication, consult a qualified physician who can provide personalized advice and details of risks and benefits based on your medical history and situation. FLCCC and WCH provide treatment protocols.
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