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loratadine (Clarityn RediTabs / Claritin Reditabs / loratadine, Zydis)

✓ Approved

Merck & Co. · HRH1 · Small Molecule

What is loratadine?

loratadine is a small molecule developed by Merck & Co.. It is approved for therapeutic indications via oral (po).

Drug Profile

Brand NamesClarityn RediTabs, Claritin Reditabs, loratadine, Zydis
CompanyMerck & Co.
Drug ClassSmall Molecule
Molecular TargetHRH1
RouteOral (PO)
StatusApproved
Sources: ClinicalTrials.gov, Merck & Co.

Mechanism of Action

Molecular Targets

loratadine acts on 1 molecular target:

HRH1histamine receptor H1 (HH1R, H1R)
Want deeper analysis?Noah AI can explain complex mechanisms and compare to similar drugs.

Therapeutic Indications

loratadine is developed for 2 unique indications across 2 therapeutic areas.

Therapeutic AreaConditionPhase
Respiratory, thoracic and mediastinal disordersRhinitis allergic✓ Approved
Skin and subcutaneous tissue disordersUrticaria✓ Approved

Related Research Articles

PubMedDrug metabolism and personalized therapy2026-07-16

The impact of antihistamine use on allergic reactions in pregnancy.

Lisiecka Maria Zofia MZ, Luczak Joanna J

Allergic diseases are common among women of reproductive age, which necessitates the use of antihistamine therapy during pregnancy while ensuring safety for both the mother and the foetus. The study aimed to determine the safety profile, pharmacological characteristics, and clinical consequences of antihistamine use during pregnancy for the maternal-foetal system. A systematic review of scientific publications for the period 2020-2025 was carried out using the PRISMA methodology with a search in five international databases, which allowed us to select 45 relevant sources analyzing pathophysiology, pharmacology, and clinical consequences. It has been established that maternal immunoglobulins of class E are transported across the placental barrier, where they may sensitise foetal mast cells in utero. Hormonal changes during pregnancy induce polarisation of the immune response towards Th2 with progressive suppression of eosinophils by 17-22 % in the second trimester and by 20-42 % in the third trimester. Population cohort studies covering more than 1.2 million pregnancies have found no statistically significant associations between the use of second-generation antihistamines and major congenital malformations, spontaneous abortions or premature births. Physiological changes during pregnancy modify the pharmacokinetic parameters of drugs, reducing plasma protein concentrations by 20-40 %, However, cetirizine and loratadine demonstrate a favourable safety profile based on data from more than 186,000 exposures in Scandinavian registries, and the relative infant dose remains below the 5 % safety threshold. The findings support the use of second-generation antihistamines as first-line therapy for allergic diseases in pregnancy and provide an evidence base for selecting safe pharmacological agents at different gestational stages.

PMID 42461140
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PubMedZhongguo zhen jiu = Chinese acupuncture & moxibustion2026-07-14

[Acupoint catgut embedding for allergic rhinitis: a randomized controlled trial].

Tang Mi M, Zhang Qinxiu Q

To observe the clinical efficacy of acupoint catgut embedding for allergic rhinitis (AR), and to explore its mechanism of action. Eighty patients with AR were randomly divided into an observation group and a control group, with 40 patients in each group. The observation group received acupoint catgut embedding therapy, with bilateral Yingxiang (LI20) as the main acupoints and additional acupoints according to syndrome differentiation. Catgut embedding was performed once every 2 weeks, for a total of 2 treatments. The control group received oral loratadine tablets. Both groups were treated for 4 weeks. Total nasal symptom scores (TNSS) and rhinoconjunctivitis quality of life questionnaire (RQLQ) scores were observed before treatment, after 2 weeks of treatment, after 4 weeks of treatment, and at 1-month follow-up after treatment in both groups. The levels of immunoglobulin E (IgE), interleukin (IL)-4, interferon-γ (IFN-γ), IL-12, and IL-13 in nasal lavage fluid were detected before and after treatment in both groups. Clinical efficacy was evaluated after treatment. After 2 weeks of treatment, after 4 weeks of treatment, and at follow-up, TNSS and RQLQ scores in both groups were lower than those before treatment (P<0.05). After 4 weeks of treatment and at follow-up, TNSS and RQLQ scores in the observation group were lower than those in the control group (P<0.001). After treatment, the levels of IgE, IL-4, and IL-13 in nasal lavage fluid were decreased compared with those before treatment in both groups (P<0.001, P<0.05, P<0.01), and the levels of IFN-γ and IL-12 were increased compared with those before treatment in both groups (P<0.001, P<0.01, P<0.05); the levels of IgE, IL-4, and IL-13 in nasal lavage fluid in the observation group were lower than those in the control group (P<0.05, P<0.001), and the levels of IFN-γ and IL-12 were higher than those in the control group (P<0.05). The total effective rate in the observation group was 95.0% (38/40), higher than 82.5% (33/40) in the control group (P<0.05). Acupoint catgut embedding could improve clinical symptoms in patients with AR, and may exert its therapeutic effect by modulating immune balance.

PMID 42443072
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PubMedIranian journal of allergy, asthma, and immunology2026-07-12

Comparison of the Efficacy of Different Doses of Glucocorticoid Nasal Spray Combined with Loratadine in the Treatment of Rhinitis in Children: A Randomized Clinical Trial.

Wang Huiying H, Ren Zhen Z

Pediatric rhinitis is a common recurrent disorder that may progress to asthma or sinusitis in severe cases. This study aimed to compare the efficacy of different doses of glucocorticoid nasal spray combined with loratadine for rhinitis in children, and provide evidence for optimizing clinical treatment. A total of 150 children with rhinitis admitted from June 2022 to June 2024 were divided into three groups: group I (low-dose group, n=50), group II (medium-dose group, n=50), and group III (high-dose group, n=50). Patients in all three groups were treated with a glucocorticoid nasal spray with loratadine combined with antihistamines. The immune function, serum inflammatory factor level, quantitative Lund-Kennedy score by nasal endoscopy, nasal symptom score, Quality of Life Questionnaire (RQLQ) scores, clinical efficacy, incidence of adverse events, and treatment compliance were assessed. Post-treatment, all indices improved in the three groups. The percentages of CD4+ and CD8+ T cells, IL-10 content, and clinical efficacy in groups II and III were significantly higher than those in group I, while the immunoglobulin E (IgE), IL-6 and IL-17 content, the quantitative Lund-Kennedy score of nasal endoscopy, the children's nasal symptom scores, the RQLQ scores, and the incidence rate of adverse events were below in group I. No significant differences were found between groups II and III in all indices, nor in treatment compliance across the three groups. Loratadine combined with a glucocorticoid nasal spray therapy effectively improves clinical outcomes, inflammation, immune function, symptoms, and quality of life in rhinitis in children, with high clinical application value.

PMID 42437310
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PubMedThe World Allergy Organization journal2026-07-12

Forecasting seasonal allergic rhinitis through integrated analysis of social media and online drug sales data.

Tong Xunliang X, Fang Chuangsen C, Jiang Xiaowei X, Liu Lan L et al.

Allergic rhinitis (AR) is a highly prevalent, seasonally variable disease that poses a growing public health challenge. Conventional surveillance based on clinic visits and surveys is slow and may miss self-medicating patients. Integrating environmental monitoring with digital traces such as search queries and online drug purchases may provide more timely insight into allergen exposure, symptom awareness, and medication demand. We analyzed daily data for urban Beijing from March 1, 2022 to October 15, 2024, including pollen concentration (grains per 1000 mm3), the Baidu search index for "allergic rhinitis," and online purchase rates of 4 oral second-generation H1-antihistamines (loratadine, desloratadine, cetirizine, levocetirizine) from the Meituan platform, standardized per 100,000 population. Cross-correlation functions were computed on pre-whitened series to assess lead-lag relationships. A single-mediator regression framework applied to pre-whitened data and estimated with Newey-West heteroskedasticity- and autocorrelation-consistent standard errors quantified the mediating role of the Baidu Index between pollen and antihistamine purchases. ARIMAX (1,1,1) models with different exogenous inputs (pollen only, Baidu Index only, both combined) and a naïve random-walk benchmark were used to forecast 1-, 2-, 3-, and 7-day demand; performance was evaluated using RMSE, MAPE, and Pearson correlation (PCC). All 3 series exhibited pronounced and recurrent seasonal patterns, with Baidu search activity rising in close temporal alignment with pollen peaks and antihistamine purchases typically lagging by 1-2 days. Pre-whitened cross-correlations remained moderate and statistically significant around lag 0, indicating genuine contemporaneous associations after removing the shared seasonal component. Mediation analysis showed that pollen concentration had a significant total effect on antihistamine purchase rates (β = 0.34, 95% CI [0.13, 0.54]), of which approximately 47% was transmitted indirectly via the Baidu Index (indirect β = 0.16, 95% CI [0.08, 0.25]). The ARIMAX (1,1,1) model integrating both pollen and Baidu Index achieved the best forecasting performance (1-day RMSE = 3.80, MAPE = 7.68%, PCC = 0.89) and consistently outperformed single-predictor models and the random-walk benchmark across all horizons. Pollen exposure influences antihistamine demand both directly and indirectly through public information-seeking behavior captured by the Baidu Index, and integrating environmental and digital data enables timely surveillance of seasonal allergic-rhinitis-related medication use.

PMID 42436900
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PubMedThe Lancet. Infectious diseases2026-07-09

Efficacy and safety of rivaroxaban, colchicine, and famotidine-loratadine with specialist supportive clinical care for fatigue in patients with post-COVID-19 condition in the UK: a multisite, open-label, randomised controlled trial.

STIMULATE-ICP consortium

Post-acute sequelae of COVID-19 or post-COVID-19 condition (also known as long COVID) affects 1-5% of adults globally, most commonly with fatigue, and no evidence-based therapies are available. We aimed to evaluate the efficacy of repurposed medications in fatigue management in adults with long COVID. We did a phase 3, four-group, randomised, controlled, adaptive platform, open-label drug trial nested within a pragmatic, multicentre, cluster-randomised trial of an integrated care pathway (ICP) for long COVID across 12 UK National Health Service (NHS) specialist long COVID care clinics in the UK. Participants had to be adults (>18 years) with long COVID who had not been hospitalised with COVID-19. In addition to NHS specialist-led long COVID care (hereafter, usual care), participants in the ICP trial could receive multiorgan MRI and clinical decision support and/or app-based rehabilitation. Initially, participants in the ICP trial were invited to enrol in the drug trial, but slow recruitment to the drug trial led to establishment of additional drug-only trial sites. Participants enrolled at either ICP trial sites or drug-only trial sites were randomly assigned (1:1:1:1) to receive colchicine 500 μg twice daily, rivaroxaban 10 mg once daily, famotidine 40 mg with loratadine 10 mg once daily, or no drug for 12 weeks. All participants received usual care. Randomisation was done electronically in blocks (various block sizes) and stratified by site, birth sex, ICP trial group allocation, and being a new or previous patient of a drug-only site. The primary endpoint was 12-week fatigue, assessed with the Fatigue Assessment Scale (FAS; with scores ranging from 10 [no fatigue] to 50 [debilitating fatigue], and a >10% change considered clinically meaningful) among randomly assigned individuals who had available baseline and 12-week data, adjusting for baseline fatigue and clinically relevant covariates. Secondary endpoints included 24-week FAS. The nested drug trial is registered, ISRCTN10665760. The trial is complete. Of 6035 eligible participants, 778 (383 co-enrolled in the ICP trial and 395 directly enrolled in the drug trial) were randomly assigned between Aug 22, 2022, and Aug 7, 2024 to colchicine (n=192), famotidine-loratadine (n=193), rivaroxaban (n=197), or no drug (usual long COVID care only; n=196). The mean age of participants was 46 years (SD 12·4), 495 (64%) of 778 were female, and 91 (12%) were from a non-White ethnic group. Across all trial groups, there was severe baseline fatigue (mean FAS score 36·8 [SD 7·49]) and a clinically relevant mean FAS reduction of 4·3 points to 32·5 (SD 9·13) at 12 weeks. Adjusted analyses showed small, statistically significant FAS reductions in the colchicine (-1·49 points [95% CI -2·92 to -0·06], p=0·041) and famotidine-loratadine (-1·48 points [-2·88 to -0·08], p=0·038) groups, but not in the rivaroxaban group (-1·06 points [-2·47 to 0·35, p=0·139), compared with no study drug at 12 weeks. However, 24-week FAS scores, 12 weeks after drug cessation, were not significantly different between groups. Treatment was well tolerated, with ten serious adverse events (requiring hospitalisation but unrelated to trial drugs) reported in eight (1·0%) of the 778 participants, five of which were in three participants in the rivaroxaban group. In participants with long COVID, severe fatigue reduced in all study groups-including the no drug group-over 12 weeks, with small additional reductions in the colchicine and famotidine-loratadine groups compared with the no drug group. Modest effects on FAS were not sustained after drug withdrawal. Long-term long COVID symptom benefit is unlikely with these drugs alone. Future trials could investigate the use of these or other repurposed drugs in specific subgroups of patients with long COVID, combination therapies, and how care is delivered. UK National Institute for Health and Care Research.

PMID 42419335
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PubMedFrontiers in oncology2026-07-02

Repurposing loratadine to induce ferroptosis and overcome multidrug resistance: preclinical evidence in KB-V-1 cells.

Cook Nicholas N, Li Xin X, Bowen Nathan J NJ, Danaher Alira A et al.

MDR1/P-glycoprotein-mediated multidrug resistance (MDR) limits chemotherapy efficacy across many cancers. Ferroptosis, an iron-dependent regulated cell death driven by lipid peroxidation, offers a potential strategy to bypass MDR. We investigated whether loratadine, an FDA-approved antihistamine, induces ferroptosis and overcomes chemoresistance in MDR1-overexpressing KB-V-1 cells. Cytotoxicity was evaluated using the CCK-8 assay in multidrug-resistant KB-V-1 cells and chemosensitive KB-3-1 cells. Ferroptosis was verified using specific inhibitors, including ferrostatin-1, liproxstatin-1, and deferoxamine, and compared with the pan-caspase inhibitor Z-VAD-FMK to exclude apoptosis. Hallmarks of ferroptosis (cystine uptake, intracellular glutathione levels, labile iron pool, and lipid peroxidation) were quantitatively assessed. Transcriptomic alterations were analyzed by RNA sequencing (RNA-seq) and further validated by quantitative real-time PCR (qRT-PCR) and Western blot analyses. In vivo antitumor efficacy was examined in a KB-V-1 xenograft model following treatment with loratadine (20 mg/kg, intraperitoneal), paclitaxel, or their combination. Loratadine selectively inhibited KB-V-1 viability (IC50 = 2.0 µM) while sparing KB-3-1 cells (IC50 =48.45 µM). Cell death was effectively rescued by ferroptosis inhibitors, confirming ferroptosis as the primary mechanism. Loratadine suppressed cystine uptake, depleted glutathione, elevated labile iron, and promoted lipid peroxidation comparably to erastin. RNA-seq identified 1,861 differentially expressed genes enriched in the PERK-eIF2α-ATF4 stress axis; upregulation of ATF4, CHAC1, DDIT4, and DDIT3 was confirmed by qRT-PCR and/or Western blot analyses. Loratadine also reduced MDR1/P-glycoprotein expression. In vivo, loratadine suppressed tumor growth and enhanced paclitaxel efficacy without systemic toxicity. Loratadine induces ferroptosis in MDR1-overexpressing cells via cystine uptake inhibition, glutathione depletion, and PERK-eIF2α-ATF4 activation, while concurrently downregulating MDR1/P-glycoprotein. These findings support loratadine as a clinically actionable repurposing candidate for ferroptosis-based, resistance-directed cancer therapy.

PMID 42388634
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