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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

PubMedNature cancer2026-11-04

Basophils inhibit early lung metastasis by suppressing regulatory T cells.

Torchia Bruno B, Fournier Nadine N, Yücel Simge S, Fournier Morgane M et al.

Basophils are rare cells best known for their role in allergy but their contribution to cancer remains poorly understood. Here, we found that basophils suppress early lung metastatic seeding in mice by enhancing antitumor CD8+ T cell immunity through inhibition of regulatory T (Treg) cells. Basophils restrain Treg cells through two complementary mechanisms: mast cell protease 8-mediated cleavage of interleukin-2 receptor α and histamine-mediated activation of the histamine H1 receptor (HRH1). HRH1 blockade with loratadine abolished Treg cell suppression and accelerated metastatic seeding in mice. In a prospective double-blind crossover trial of loratadine versus placebo enrolling 40 healthy volunteers ( IRCT20170608034390N14 ), circulating Treg cell frequency (primary outcome) increased following loratadine. Higher blood basophil counts predicted improved survival across human cancers and integrative multiomic analyses identified conserved quiescent (B0) and tumor-associated (B1) basophil states, with B0 predicting favorable outcomes. These findings identify basophils as regulators of early metastatic progression and highlight the basophil-Treg cell axis as a potential therapeutic target.

PMID 42977840
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PubMedMolecular pharmaceutics2026-11-02

Structural Response of Amorphous Active Pharmaceutical Ingredients with Flexible Molecules to High Pressure.

Janowska Anna A, Garbarino Gaston G, Rodrigues Joao Elias F S JEFS, Gallego Parra Samuel S et al.

The objective of this study was to examine the intra- and intermolecular structure of two active pharmaceutical ingredients characterized by van der Waals flexible moleculesprobucol and loratadinein their liquid and glassy states under ambient and high-pressure conditions. We investigated how compression influences local packing motifs in these systems and whether the structural features observed in supercooled liquids under ambient and high-pressure conditions resemble those found in ordinary and pressure-densified glasses. Structural evolution was characterized using ambient- and high-pressure X-ray diffraction supported by molecular dynamics simulations. Total and partial structure factors, pair distribution functions, and local structural parameters were calculated from molecular dynamics models that were consistent with experimental diffraction data. The results show that compression primarily modifies local molecular packing and the distribution of various intermolecular contacts while inducing only minimal changes in the conformations of these flexible molecules. Regarding the intermolecular structure, compression affects the medium-range order, increases local structural heterogeneity, and enhances the population of short O-H···S and Cl···Cl contacts. These features are less pronounced in the corresponding liquid and glass states at ambient pressure, within the pressure and temperature ranges studied here, as well as in crystal structures. Upon decompression, these structural characteristics may either relax or exhibit partial similarity to those observed in supercooled pressurized liquids. While analogous phenomena have been discussed for glasses with highly interconnected networks (such as silica-based glasses), our results indicate that similar effects can also appear in molecular pharmaceutical systems. Our results provide molecular-level insight into pressure-induced structural organization in pharmaceutical liquids and motivate further studies on how such structural changes may relate to the properties of the resulting glassy states.

PMID 42969720
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PubMedACS omega2026-10-25

Loratadine Decreases Methicillin-Resistant Staphylococcus aureus Virulence through Global Hemolysin Regulators vraSR and agr.

Dillon Chase C, Marshall Isabel I, Henkel Maggy M, Balogh Halie H et al.

Methicillin-resistantStaphylococcus aureus-(MRSA) is a bacterial pathogen that relies on expression of a wide range of virulence factors. Hemolysins are a diverse collection of cytolytic toxins that promote virulence by being excreted and lysing host blood cells. We previously reported on novel antivirulence compounds that modulate hemolysis in vitro, including a brominated carbazole (compound 8) and the active ingredient in Claritin (loratadine). We analyzed expression and activity of MRSA hemolysins in two hospital-acquired strains. Even with the same staphylococcal cassette chromosome mec (SCCmec) type, the strains displayed unique responses to loratadine where both repression and elevation of hemolysis occurred. These compounds are potentially binding and regulating the master regulatory protein, Stk1, which has known ties to hemolysis inS. aureus. We hypothesized that the modulation of hemolysis by these putative Stk1 inhibitors would extend to community-acquired strains of MRSA. Furthermore, we wanted to determine if Stk1 was the only hemolysis regulatory protein being engaged by these compounds. To test this, we examined compound 8 and loratadine effects on two different USA300 strains, in addition to transposon mutants for a range of hemolysis regulatory genes. We observed strain-specific regulation of hemolysis by Stk1. Loratadine continued to downregulate both alpha and beta hemolytic activity in USA300 JE2 in both Stk1-dependent and independent pathways. Additionally, we report that this antivirulence compound effectively disrupts hemolysis by modulating both agr and vraSR global regulators, contributing to widespread cytotoxin repression. Both alpha hemolysin (hla) and RNAIII/delta hemolysin (hld) mRNA reductions occurred in vitro and in a human cell line model of MRSA infection. Together, these results expand our knowledge of loratadine's mode of action as a virulence modulator.

PMID 42923371
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PubMedChemSusChem2026-10-23

Direct α-C(sp3)─H Alkylation and Arylation of Ethers Enabled by Carbon Nitride/Nickel Metallaphotoredox Catalysis.

de Vries Ibáñez Miguel M MM, Husy Nathan G G NGG, Inico Elisabetta E, Karaca Kaan K et al.

The direct functionalization of α-C(sp3)─H bonds offers a powerful strategy for converting abundant feedstocks and complex molecules into value-added products, yet sustainable catalytic platforms that avoid precious-metal photocatalysts remain underdeveloped. Here, we report a metallaphotoredox system that combines recyclable carbon nitride nanosheets with nickel catalysis for the direct α-C(sp3)─H cross-coupling of ethers, amides, and benzylic substrates under visible light. The method operates at mild temperature in air and enables both α-C(sp3)─C(sp2) and α-C(sp3)─C(sp3) bond formation using aryl and alkyl halides, including challenging ether donors such as THF, 2-MeTHF, 1,4-dioxane, and DME. Broad functional group tolerance is demonstrated across electronically diverse aryl halides, while late-stage alkylation of pharmaceutically relevant molecules including loratadine, caffeine, and fenofibrate highlights the utility of the platform for molecular diversification. The carbon nitride photocatalyst is readily recovered and reused over five cycles without loss of activity, and the process is further translated to continuous flow, providing accelerated reaction kinetics and reduced photocatalyst loading. Mechanistic studies combining Stern-Volmer analysis, radical trapping, cyclic voltammetry, NMR spectroscopy, and DFT calculations support a dual catalytic cycle in which photoexcited carbon nitride promotes oxidative generation of α-heteroatom-stabilized radicals, while nickel mediates radical capture, cross-coupling, and product-forming reductive elimination. This work establishes carbon nitride as an earth-abundant, recyclable alternative to noble-metal photocatalysts for metallaphotoredox C─H functionalization and expands the scope of heterogeneous photocatalysis to direct α-C(sp3)─H cross-coupling.

PMID 42912554
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PubMedRSC advances2026-10-17

Functional evaluation of loratadine-cyclodextrin complexes: comprehensive solid-state characterisation, biopharmaceutical assessment and stability profiling.

Pocrnić Marijana M, Potrzebowski Marek J MJ, Jug Mario M, Galić Nives N

Loratadine (LOR) is a poorly water-soluble antihistaminic drug whose solubility can be significantly enhanced in water and biorelevant media through inclusion complexation with β-cyclodextrins (β-CDs), as we have shown previously. In this work, we investigated the biopharmaceutical properties and chemical stability of LOR : β-CDs 1 : 1 and 1 : 2 complexes in the solid state, prepared by two different methods: (i) solvent-free mechanochemical grinding in a high-energy vibrational mill, and (ii) spray-drying, as a traditional solvent-based technique. Altogether, 16 different systems were prepared using LOR, β-CD and its derivatives, namely hydroxypropyl-β-cyclodextrin (HP-β-CD), randomly methylated-β-cyclodextrin (RM-β-CD), and sulfobutylether-β-cyclodextrin (SBE-β-CD). Detailed solid-state characterization by differential scanning calorimetry (DSC), X-ray powder diffraction, ATR-FTIR and solid-state NMR was performed, indicating different levels of drug amorphization. Biopharmaceutical evaluation via in vitro dissolution testing and in vitro permeability assay across biomimetic membranes revealed that LOR dissolution and permeability depend on CD's type, LOR-to-CD molar ratio, and the method used for complex preparation. The influence of β-CDs on LOR stability under stress conditions, including photostability and accelerated stability studies, was determined using UHPLC-HR MS/MS. The structures of degradation products, including five previously unknown, were proposed. Obtained complexes, especially those prepared by grinding, demonstrated great potential for further formulation development.

PMID 42889714
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PubMedInternational journal of molecular sciences2026-10-16

Unveiling Novel Molecular Candidate Targets of Loratadine, Raloxifene, and Sorafenib in Hepatocellular Carcinoma.

Villarruel-Melquiades Fernanda F, Noyola-Díaz Martha M, Martínez-Gudiño Gelacio G, Mendoza-Garrido María Eugenia ME et al.

Hepatocellular carcinoma (HCC) remains a major global health burden. We have recently demonstrated the synergistic cytotoxicity elicited by the combination of loratadine, raloxifene, and sorafenib in liver cancer cells. In this study, we investigated the potential mechanistic basis of this novel multi-drug regimen by identifying candidate protein targets of the three drugs. Potential protein targets of each drug were identified using the Drug Affinity Responsive Target Stability (DARTS) assay in protein extracts from the HCC cell line HuH7, and molecular docking was performed to predict binding modes and explore the structural feasibility of these drug-target interactions. Bioinformatics analyses were conducted to predict biological functions, molecular interactions, and clinical relevance. We identified 147 potential candidate DARTS-stabilized proteins for loratadine, 191 for sorafenib, and 157 for raloxifene; a proportion of these candidate proteins maintained a statistically significant association with overall survival in HCC patients: 20.14% for loratadine, 22.93% for raloxifene, and 24.47% for sorafenib. Cross-referencing with public databases confirmed several previously documented targets-complementing our experimental approach-while revealing numerous previously unreported target candidates. Docking analyses predicted favorable binding interactions between the drugs and several proteins, such as the putative complex between loratadine and N-glycanase 1 (NGLY1), whose expression correlates with reduced overall survival in HCC patients. Functional enrichment analysis showed that several targets are involved in hallmarks of cancer. Clinically relevant candidate targets of loratadine, raloxifene, and sorafenib were identified. However, as these candidate protein targets were identified exclusively in HuH7 cells, they may not fully generalize across all HCC models without further validation. Nevertheless, our results suggest that loratadine, raloxifene and sorafenib modulate key pathways involved in tumorigenesis. These findings strengthen the use of this combination as a promising therapeutic strategy for HCC and provide new opportunities for the identification of novel targets, prognostic markers, and molecular vulnerabilities suitable for pharmacological intervention in HCC and other malignancies and diseases.

PMID 42883895
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