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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

PubMedFrontiers in medicine2026-08-28

Second-generation H1 antihistamines for the treatment of chronic urticaria: a network meta-analysis.

Li Zixuan Z, Zhang Juan J, Zheng Yaqi Y, Zhang Mingyan M et al.

To evaluate the efficacy and safety of 10 commonly used second-generation H1 antihistamines (cetirizine, levocetirizine, loratadine, desloratadine, ebastine, bilastine, olopatadine, rupatadine, fexofenadine, and mizolastine) at licensed doses in treating chronic urticaria using network meta-analysis. Seven electronic databases were searched, including PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data Knowledge Service Platform, and Chinese Biomedical Literature Service System. Relevant literature from inception to the end of December 2025 was retrieved. Studies meeting the criteria were selected, and network meta-analysis was performed using Stata 16 software. A total of 54 studies involving 7,290 patients were included. Network meta-analysis indicated that olopatadine, mizolastine, bilastine, and levocetirizine were more effective than placebo in improving total symptom scores. All 10 drugs were superior to placebo in reducing itching scores, although only fexofenadine achieved statistical significance. For reducing wheal scores, ebastine was significantly more effective than mizolastine and loratadine. Regarding adverse reactions, no significant differences were observed between any of the drugs and placebo, with fexofenadine having the lowest adverse reaction rate. Sensitivity analyses excluding highrisk studies confirmed the robustness of findings across all outcomes. Based on current evidence, olopatadine at licensed dose exhibited the best efficacy in reducing total symptom scores. Fexofenadine was most effective for improving itching scores and ebastine was optimal for reducing wheal scores. In addition, fexofenadine had the lowest incidence of adverse reactions. However, the conclusions of this study still need to be validated by further high-quality randomized controlled trials.

PMID 42662818
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PubMedInternational journal of molecular sciences2026-08-27

Serum Peptidomic Analysis in a Comparative Study of the Efficacy of Benjakul Remedy Versus Loratadine in Allergic Rhinitis Patients.

Tiyao Vilailak V, Roytrakul Sittiruk S, Jaresitthikunchai Janthima J, Charoenlappanit Sawanya S et al.

Benjakul (BJK) remedy, traditionally used to balance the four elements, has demonstrated clinical efficacy in relieving inflammation and allergic rhinitis (AR) symptoms. This study investigated differential serum peptide expression in AR patients treated with BJK remedy compared to loratadine using MALDI-TOF MS and LC-MS/MS. MALDI-TOF MS revealed four shared mass peptide patterns that were significantly upregulated (p < 0.05) after 3 and 6 weeks of both treatments. Identifying the peptides, 17β-hydroxysteroid dehydrogenase (17β-HSD) and microtubule-actin cross-linking factor 1 (MACF1) were linked to inflammatory suppression and hormonal balance, while zinc finger CCCH-type containing 4 (ZC3H4) and transducin beta-like protein 3 (TBL3) were associated with the relief of pulmonary fibrosis. Conversely, zinc finger homeobox 3 (ZFHX3) and transformation/transcription domain-associated protein (TRRAP) remained elevated after treatment, potentially promoting persistent inflammation via E2F transcription factor 1- (E2F1-) and E2F transcription factor 4- (E2F4-) mediated transcription. Among 1113 peptides identified by LC-MS/MS (selected using a significance threshold of p < 0.05, without a fixed fold-change cutoff), 6-week treatment with BJK remedy significantly downregulated UBQLN1 (4.562-fold; p = 0.016), suppressing toll-like receptor (TLR) activation and B-cell proliferation. It also upregulated Prostaglandin E synthase 2 (PTGES2) and PDZ and LIM domain protein 2 (PDLIM2) (7.841-fold and 8.697-fold, respectively; p = 0.004 and 0.002), while enhancing antioxidant and immunoregulatory responses via ATP-binding cassette subfamily B member 8 (ABCB8) and ADP-ribosylation factor GTPase-activating protein 3 (ARFGAP3). By comparison, 3 weeks loratadine treatment significantly downregulated E2F transcription factor 3 (E2F3) and general transcription factor IIIC subunit 6 (GTF3C6) (p = 0.034 and 0.017) and upregulated CTD small phosphatase like 2 (CTDSPL2), suggesting a distinct but complementary anti-inflammatory mechanism. Together, these findings enhance the understanding of AR pathophysiology and may help to elucidate the mechanisms of BJK remedy and loratadine in treatment, supporting the further development of targeted therapies and biomarkers.

PMID 42653391
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PubMedCancers2026-08-27

Antineoplastic Activity of the Combination Loratadine-Simvastatin-Gefitinib in HPV-Positive Cervical Cancer Cells: In Vitro and In Vivo Studies.

Raya-Bahena Tania T, Rivera-Escobar Rene M RM, Hernández-Gallegos Elisabeth E, Jiménez-Salazar Javier E JE et al.

Background/Objectives: Cervical cancer (CC) is the most clinically significant HPV-associated malignancy. Platinum-based chemotherapies produce drug resistance and serious adverse effects. Drug repurposing and combinations are promising approaches to improve the antitumor response. Here, we evaluated the antineoplastic potential of loratadine and simvastatin alone and in combination with cisplatin and gefitinib in HPV-positive CC cells. Methods: HeLa and SiHa CC cells were treated with loratadine, simvastatin, cisplatin, gefitinib, or their combinations. Metabolic activity was assessed using the MTT assay to determine drug inhibitory concentrations (IC20, IC50) from concentration-response curves. Apoptosis was assessed by Annexin V-FITC/PI flow cytometry. Clonogenic survival and migratory capacity were evaluated using colony formation and wound-healing assays, respectively. Tumor formation was evaluated in vivo using the chick chorioallantoic membrane model. Results: Metabolic activity decreased in a concentration-dependent manner following drug treatment in both cell lines. Several combination regimens at IC20 significantly improved reductions in metabolic activity and increases in apoptosis compared with monotherapies or two-drug combinations. Notably, some three-drug combinations, with or without cisplatin, had similar effects to the quadruple regimen. Combination treatments also reduced clonogenic survival and migratory capacity, as well as tumor formation and cancer cell dissemination in vivo. Conclusions: Drug combinations at relatively low concentrations (IC20) significantly enhanced the anticancer effects on CC cells in in vitro and in vivo settings. These findings support the potential of drug repurposing and combination strategies as promising approaches to decrease adverse side effects while improving therapeutic efficacy for the benefit of CC patients.

PMID 42649903
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PubMedCureus2026-08-16

New-Onset Seizure Following Loratadine and Alcohol Ingestion: A Case Report.

Denecke Morgan M, Stack Thomas T, Beall Jackson J, Oliver Joshua J

Loratadine is a common over-the-counter second-generation H1-antihistamine used to relieve and treat seasonal allergy symptoms. While first-generation H1-antihistamines are historically known to cause central nervous system (CNS) side effects, these effects are thought to be far less common in second-generation antihistamines. Similarly, alcohol is known to have CNS effects. We report a case of a 26-year-old female who presented to the emergency department (ED) after a suicide attempt involving loratadine and alcohol ingestion. Emergency medical services (EMS) reported that the patient became unresponsive upon arrival at the ED. An empty loratadine bottle that was supposed to contain 60 tablets was found at the scene. Additionally, an empty bottle of wine was also found at the scene. Initial vital signs and glucose levels were normal, but on examination, the patient had a Glasgow Coma Scale of 3 with rightward eye deviation and developed tonic-clonic seizures, which were quickly controlled with 4 mg of intravenous (IV) lorazepam. She gradually regained responsiveness and received 3200 mg of levetiracetam IV. Toxicological workup revealed a serum ethanol level of 119 mg/dL and a urine toxicology screen positive for benzodiazepines, likely due to lorazepam administration. The patient had mildly elevated lactate and creatine kinase levels consistent with seizure, which normalized after fluid resuscitation. The patient recovered fully without further seizures and was not prescribed antiepileptic medication upon discharge. We present the case to document a potential seizure provoked by the combined ingestion of loratadine and alcohol.

PMID 42604277
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PubMedBMJ (Clinical research ed.)2026-07-30

Antihistamines for atopic dermatitis (eczema): systematic review and network meta-analysis of randomised trials.

Chu Alexandro W L AWL, Wen Aaron A, Guyatt Gordon H GH, Rao Muhammad M et al.

To systematically synthesise the benefits and harms of add-on oral antihistamines for managing atopic dermatitis (eczema). Systematic review and network meta-analysis of randomised trials. Medline, Embase, CENTRAL, the United States Food and Drug Administration, and the European Medicines Agency databases from database inception to 5 May 2025. Randomised trials assessing add-on oral H1 antihistamines, H2 blockers, mast cell stabilisers (nedocromil sodium and sodium cromoglycate), or their combinations. Paired reviewers independently screened records, extracted data, and assessed risk of bias using a modified Cochrane Risk of Bias tool version 2. Random effects bayesian meta-analyses synthesised atopic dermatitis severity (oSCORAD-objective scoring atopic dermatitis, 0-83; minimal important difference 8.2; lower better), itch severity (numerical rating scale, 0-10; minimal important difference 3; lower better), sleep disturbance, atopic dermatitis related quality of life, and harms. The network meta-analysis GRADE (Grading of Recommendations Assessment, Development and Evaluation) and Core GRADE approaches informed certainty of evidence ratings. 47 trials enrolled 6230 children and adults with primarily moderate to severe atopic dermatitis. With moderate certainty, compared with placebo, adding a first generation or second generation H1 antihistamine likely resulted in a small reduction in atopic dermatitis severity (mean difference -1.87, 95% credible interval -3.47 to -0.27) and itch severity (-0.89, -1.41 to -0.37). Although statistically detectable, these effects are well below established minimal important differences (smallest change in an outcome that a patient would identify as important). With low certainty, all studied interventions may not improve sleep disturbance or reduce atopic dermatitis exacerbations. First generation agents probably increase cognitive impairment and may increase treatment discontinuation because of adverse events (risk difference 66 more per 1000, 95% credible interval 0 to 231 more; moderate certainty). Second generation agents differ in their risk of cognitive impairment (range of mean effects 0 more per 1000 for loratadine, 16 more per 1000 for levocetirizine, and 17 more per 1000 for cetirizine). Among patients with atopic dermatitis, adding H1 antihistamines probably results in a clinically unimportant reduction in atopic dermatitis severity and itch severity, and may not reduce sleep disturbance or atopic dermatitis exacerbations. First generation agents increase cognitive impairment and may increase treatment discontinuation because of adverse events. Cognitive impairment risk differs among second generation agents. These findings provide evidence against routine antihistamine use in atopic dermatitis management and will inform updated clinical guidelines. PROSPERO CRD42022345643.

PMID 42526949
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PubMedEuropean journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences2026-07-29

Combined second harmonic and linear light scattering as a tool for solubility and aggregation screening.

Kalasová Jitka J, Tarun Orly O, Kuentz Martin M

Poor aqueous solubility and complex supersaturation behaviour of small-molecule drugs require rapid, material-sparing analytical tools that capture incipient aggregation and phase separation events under non-equilibrium conditions. This work evaluated a miniaturised optical platform that combined second harmonic scattering (SHS) with linear light scattering (LLS) driven by an ultrafast 1030 nm laser to monitor supersaturated solutions of 12 poorly water-soluble drugs prepared by DMSO solvent shift in 384-well plates. LLS and SHS signals were recorded after 1 h and 24 h and compared with apparent solubilities from a parallel solvent-shift HPLC assay. LLS, which reports on particle size/number, detected precipitation onsets typically close to or below HPLC values and could resolve particle formation down to ∼ 0.1 µM for pimozide, substantially exceeding the sensitivity of standard nephelometric methods. SHS, which is sensitive to interfacial asymmetry and nonlinear susceptibility, often showed onsets and complex peak-drop-rise patterns that deviated from LLS, particularly for lopinavir, loratadine, and ritonavir, indicating structurally distinct, largely centrosymmetric drug-rich assemblies above the solubility limit. Orthogonal characterization by scanning electron microscopy, Capflex (capillary flow with a hydrophobic fluorescent tracer), and confocal fluorescence microscopy provided independent evidence for droplet-like or amorphous drug-rich domains that preceded bulk precipitation. Together, the results showed that combined SHS-LLS enabled highly sensitive detection of precipitation, while revealing multistep, non-classical aggregation pathways in pharmaceutical supersaturated systems.

PMID 42521104
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