Continuing Education Activity

Loratadine is a widely utilized second-generation antihistamine prescribed for the management of allergic rhinitis and urticaria, conditions that frequently disrupt daily functioning and quality of life. Its selective action on peripheral H1 receptors helps reduce symptoms such as sneezing, itching, and rhinorrhea while limiting sedative effects. This activity reviews the clinical applications of loratadine, including its mechanism of action, contraindications, dosing recommendations across patient groups, pharmacokinetic characteristics, potential adverse reactions, and essential drug interaction considerations. A clear understanding of these principles enables clinicians to prescribe loratadine safely and effectively.

This activity also highlights the essential role of the interprofessional healthcare team in ensuring optimal use of loratadine. Collaborative practice supports accurate medication reconciliation, comprehensive patient counseling, and ongoing monitoring, particularly for individuals with hepatic or renal impairment or those at elevated risk for medication-related complications. By applying evidence-based guidance, clinicians can enhance treatment precision, reduce the likelihood of adverse events, and improve therapeutic outcomes. Through coordinated and informed care, healthcare professionals can promote the safe and effective integration of loratadine into patient management plans.

Objectives:

• Assess renal and hepatic function in patients before initiating loratadine therapy.
• Identify potential adverse effects and implement strategies to minimize loratadine-related toxicity.
• Implement safe administration techniques for different loratadine formulations, including tablets, orally disintegrating tablets, capsules, and syrup.
• Collaborate with interprofessional team members to optimize loratadine therapy and improve outcomes in allergic rhinitis and urticaria.

Indications

Antihistamines are classified as first-generation and second-generation antihistamines. First-generation antihistamines such as diphenhydramine, chlorpheniramine, promethazine, and hydroxyzine are lipophilic and cross the blood-brain barrier, leading to sedation and anticholinergic adverse effects. Second-generation antihistamines, including loratadine, cetirizine, azelastine, rupatadine, and bilastine, act selectively on peripheral H1 receptors, resulting in reduced sedation and a long half-life, which may permit once-daily dosing depending on the clinical situation. A "third generation" is an informal classification that denotes active metabolites or refined derivatives of second-generation agents, such as fexofenadine, desloratadine, levocetirizine, and carebastine. These agents demonstrate improved safety and tolerability; for instance, fexofenadine is the active metabolite of terfenadine, which was withdrawn due to QT prolongation and the risk of torsades de pointes.[1][2] However, third-generation antihistamine terminology is not formally recognized by the US Food and Drug Administration (FDA).

FDA-Approved Indications

Loratadine is a piperidine histamine H1-receptor antagonist with anti-allergic properties but without sedative effects. The drug is an FDA-approved medication for the relief and treatment of allergic rhinitis (hay fever) and urticaria (an allergic skin rash).[3][4][5] Loratadine is an effective, second-generation antihistamine used to relieve pruritus, watery eyes, runny nose, and sneezing associated with seasonal allergies.[6] Loratadine is available both by prescription from the patient's clinician and as an over-the-counter (OTC) medication, both branded and generic. Loratadine is considered safe to use in the geriatric population and in children older than 2. The drug was involved in controversy as 1 of the first direct-to-consumer advertised drugs, leading to further FDA clarification on required drug advertising content.[7] The drug was petitioned for OTC availability in 1998, and the FDA granted the petition. The original manufacturer made their product available OTC in 2002.[8] According to the American Academy of Allergy, Asthma & Immunology, second-generation antihistamines, such as loratadine, are considered the initial treatment of choice for chronic urticaria.[9] The American Academy of Otolaryngology-Head and Neck Surgery endorses the use of loratadine for allergic rhinitis (seasonal and perennial).[10] The FDA has also approved loratadine-pseudoephedrine, a fixed-dose combination of loratadine and pseudoephedrine, which is a nasal decongestant. A single dose of loratadine-pseudoephedrine rapidly and significantly improves nasal airflow in allergic rhinitis due to the decongestant effect of pseudoephedrine.[11] However, intranasal corticosteroids remain the cornerstone of long-term therapy.[12][13]

Off-Label Uses

Eczema/atopic  dermatitis (adjunct): The safety, availability, and affordability of oral antihistamines, whether OTC or prescription, have contributed to their popularity for treating pruritus associated with atopic dermatitis. Nonetheless, the pathophysiology of itch in atopic dermatitis is predominantly non-histaminergic, indicating that antihistaminergic agents may have limited efficacy. Furthermore, a systematic review of second-generation antihistamines, such as fexofenadine, cetirizine, and loratadine, found no evidence supporting their effectiveness in alleviating itching associated with atopic dermatitis.[14] However, if the patient has coexisting pathologies, such as allergic rhinitis and eczema, then antihistamines can be a valuable option.[15]

Vancomycin-induced flushing: A case report describes the off-label use of loratadine to control histamine-mediated flushing in vancomycin-induced red-man syndrome. However, symptom resolution typically requires prompt discontinuation of vancomycin.[16]

Filgrastim-induced bone pain: Bone pain is the most common adverse effect in cancer patients receiving granulocyte colony-stimulating factor (G-CSF) to prevent febrile neutropenia. The study evaluated the use of combined H1- and H2-receptor blockers (loratadine and famotidine) to prevent G-CSF–induced bone pain, which is thought to arise from histamine release and its effects on bone marrow nociceptors. Adult female patients with solid tumors who developed significant bone pain while receiving filgrastim were treated with dual histamine blockade before subsequent doses, resulting in notable pain relief. This suggests that blocking histamine receptors may mitigate G-CSF–induced bone pain. Larger randomized trials are needed to validate these findings.[17][18][19][20]

Mechanism of Action

Loratadine is a long-acting, second-generation, nonsedating tricyclic antihistamine (piperidine derivative) with selective antagonistic properties to peripheral histamine H1 receptors. Loratadine selectively inhibits H1 receptors primarily on respiratory smooth muscle cells, vascular endothelial cells, gastrointestinal tract cells, and immune cells. Unlike first-generation antihistamines such as diphenhydramine, loratadine is a competitive histamine antagonist that crosses the blood-brain barrier only minimally due to the P-glycoprotein–mediated efflux.[21] Therefore, it minimally affects central nervous system (CNS) neurons, thereby preventing daytime somnolence or sedation.[22][23]

Loratadine binds to H1 receptors in different cells and reduces vascular permeability (prevents edema and flushing), lowers smooth muscle tone (bronchodilation), and decreases the activation of peripheral nociceptive receptors (decreases pain and pruritus). At high concentrations, second-generation antihistamines such as loratadine can inhibit histamine release from mast cells and basophils, thereby reducing ICAM-1 expression in epithelial cells and inhibiting type 1 hypersensitivity reactions (eg, hay fever, urticaria, pruritus, edema).[24] There is also evidence of anti-inflammatory properties with second-generation antihistamines.[25] 

Pharmacokinetics

Absorption: After oral administration, loratadine is rapidly absorbed and undergoes extensive first-pass metabolism. Loratadine has a fast onset of action, usually within 1 to 3 hours, with peak effects occurring between 8 and 12 hours.

Distribution: Loratadine is highly bound to plasma proteins, with 97% to 99% binding affinity. Its active metabolite, desloratadine, is moderately bound, with 73% to 76% binding. The volume of distribution of loratadine is approximately 120 L/kg.[PubChem. Access date 12.4.25] The affinity of second-generation antihistamines for P-glycoprotein (P-gp) at the blood-brain barrier may explain the lack of CNS adverse effects.[26][21]

Metabolism: Loratadine undergoes oxidative metabolism primarily via cytochrome P450 enzymes CYP3A4 and CYP2D6, producing its active metabolite, desloratadine. The metabolic process involves oxidation, forming desloratadine, which accounts for most of the drug’s pharmacological activity. Subsequently, desloratadine is further metabolized by CYP2C8 after UGT2B10-mediated glucuronidation, resulting in 3-hydroxydesloratadine.[27][28]

Excretion: Approximately 40% of the dose is recovered in the urine and 42% in feces, predominantly as conjugated metabolites. About 27% of the dose is eliminated in urine within the first 24 hours. Less than 1% of the active compound is excreted unchanged, either as loratadine or desloratadine. The half-life of loratadine is approximately 8 hours, while that of desloratadine is approximately 28 hours. [PubChem. Access date 12.4.25]

Administration

Available Dosage Forms and Strength

Loratadine is available as tablets (chewable or orally disintegrating tablets [ODTs]), liquid-filled capsules, or a syrup (1 mg/mL solution). The medication can be administered orally with or without meals, though it is generally recommended to take it on an empty stomach. The dispersible tablet is placed in the mouth and allowed to dissolve. The patient may swallow it with or without water. Research is underway for other formulations designed to increase bioavailability.[29]

Adult and Pediatric Dosing

Allergic rhinitis:

• In adolescents, adults, and geriatrics: 10 mg orally once daily or 5 mg twice daily; do not exceed 10 mg in 24 hours.
• In pediatrics: 5 mg orally once daily (in children aged 2 to 5); 10 mg once daily (in children aged 6 and older). The ODT formulation is not recommended for younger children.

Urticaria:

• In adolescents, adults, and geriatrics: 10 mg orally once daily; generally, dosing should not exceed 10 mg in 24 hours. However, some patients may benefit from higher doses. Clinicians should weigh the risks against the benefits.
• In pediatrics: 10 mg orally daily as needed (in children aged 6 and older).

Specific Patient Populations

Renal impairment (creatinine clearance of less than 30 mL/min): In both renal and hepatic insufficiency, the recommendation is to increase the dosing interval to 48 hours, as follows:

• In adults: 10 mg orally every other day.
• In children aged 2 to 6: 5 mg orally every other day.
• In children older than 6: 10 mg orally every other day.
• Patients on peritoneal or hemodialysis should be dosed every 48 hours; no supplemental dose is required after dialysis.

Hepatic impairment: The drug's half-life increases with the increasing severity of the hepatic disease. Therefore, dosing requires careful adjustment.

• In adults: 10 mg by mouth every other day.
• In children aged 2 to 6: 5 mg by mouth every other day.
• In children older than 6: 10 mg by mouth every other day.

Pregnancy considerations: Loratadine should be safe for use during pregnancy; the risk of harm to the fetus is not expected based on limited human data; however, risk-benefit evaluation and counseling of the mother is required. There is no known risk of infant harm based on the drug's properties and currently limited data in humans. Loratadine and cetirizine are among the best-studied second-generation antihistamines and are generally considered safe for the control of allergic rhinitis during pregnancy.[30][31] The results of meta-analysis indicate that the use of loratadine during pregnancy does not significantly increase the risk of hypospadias.[32]

Breastfeeding considerations: Caution is advised; nursing mothers may use the medication for a short time. Both loratadine and its active metabolite pass readily into breast milk. There is no known risk of infant harm based on the drug's properties and the currently limited human data. Loratadine has minimal sedative effects and low concentrations in breast milk, and its use in breastfeeding women is not generally expected to cause adverse effects in breastfed infants. However, potential effects on lactation should be considered, particularly when loratadine is administered in combination with sympathomimetic agents such as pseudoephedrine. The British Society for Allergy and Clinical Immunology advises using the lowest effective dose of either chlorphenamine or loratadine when an antihistamine is indicated during breastfeeding. The administration of high-dose antihistamines by the parenteral route may reduce basal serum prolactin levels in nonlactating and early postpartum women; however, antihistamine pretreatment does not appear to affect suckling-induced prolactin secretion in postpartum women. Data regarding whether lower oral doses of antihistamines exert similar effects on serum prolactin or impact breastfeeding outcomes are lacking. In women with established lactation, prolactin levels may not influence breastfeeding capability.[33][34] 

Pediatric patients: Loratadine dosing in pediatric patients is outlined above.[35]

Older patients: Loratadine is subject to half-life variability in older patients, and clinicians should be mindful of this factor when initiating therapy in this age group. However, according to the American Geriatrics Society (AGS) Beers Criteria 2025, first-generation antihistamines should be avoided. For older patients, second-generation antihistamines such as loratadine are preferred.[36]

Adverse Effects

Although loratadine is a relatively safe and effective medication for treating allergic rhinitis, its primary adverse effects include headaches, dizziness, and gastrointestinal distress (diarrhea, abdominal pain, nausea, and vomiting). Loratadine may also cause sedation (a rare adverse effect), mydriasis, and xerostomia. These effects are primarily due to the drug's anticholinergic properties; anticholinergic adverse effects are minimal at therapeutic dosage.[37][38][39] In a patient undergoing long-term loratadine treatment, a rare case of bilateral cystoid macular edema has been described, which resolved after discontinuation of loratadine. The potential pathophysiology remains unclear. It may involve dysfunction of H1-receptor–expressing retinal neurons and associated signal transduction, toxicity affecting Müller cells or retinal pigment epithelium cells, and intracellular fluid accumulation.[40]

Drug-Drug Interactions 

CNS depressants: Concurrent use of CNS depressants, such as diphenhydramine, dextromethorphan, opioids, or benzodiazepines, with loratadine may increase the risk of sedation.

Pitolisant: Pitolisant is a histamine-H3 receptor antagonist and inverse agonist that increases histamine release in the brain, promoting wakefulness. H1 antihistamines block histamine's action at postsynaptic receptors, potentially reducing Pitolisant's effectiveness and causing sedation. Concurrent use may blunt Pitolisant's benefits in narcolepsy. Avoid or monitor this combination closely.[41]

Betahistine: Betahistine is an analog of histamine, and it may have interactions with other antihistamine drugs; therefore, combinations of betahistine with antihistamines are not advisable. 

Amiodarone: Loratadine has been reported to cause torsades de pointes in rare cases by prolonging the QT interval. TdP associated with chronic amiodarone treatment may occur when amiodarone is coadministered with loratadine, which may potentially prolong the QT interval.[42][43][44]

CYP450-mediated interactions: While loratadine has no dangerously significant drug-drug interactions, as with any drug, thorough medication reconciliation is necessary. Drugs that affect the CYP450 enzyme system may have interactions that require therapy modification.[45] Loratadine is principally metabolized by CYP3A4 and CYP2D6, which may result in pharmacokinetic interactions with CYP3A4 inhibitors such as azole antifungals, clarithromycin, and erythromycin, as well as grapefruit juice.[46]

Contraindications

Contraindications to loratadine include patients with documented hypersensitivity to the drug or components of the formulation, with strong contraindications in children younger than 2 due to its antihistamine properties, which may cause CNS stimulation or seizures in young patients.

Warnings and Precautions

Though the medication is generally nonsedating, patients who perform activities requiring concentration, such as driving a motor vehicle, should be advised to use caution, as it may cause mild drowsiness. Patients diagnosed with phenylketonuria should speak with their primary care physician before taking loratadine. Some of its formulations (eg, ODTs) may contain phenylalanine, which may exacerbate the symptoms of phenylketonuria. 

Patients with liver disease or hepatic impairment are advised to exercise caution as the liver extensively metabolizes loratadine, and dose adjustments may be necessary per healthcare guidelines. Similarly, individuals with kidney failure or renal impairment should be cautious, as such patients may have elevated loratadine concentrations, requiring dose adjustments.[47][48]

Monitoring

Patients taking loratadine require monitoring for symptomatic relief, sedation, and potential anticholinergic effects, including mydriasis and dry oral mucosa (which are infrequent at therapeutic doses). Renal and hepatic function should also be closely monitored by the primary care physician in patients with kidney or liver impairment, with appropriate dose adjustments made accordingly. Cardiac function should also be observed in individuals with a history of cardiac arrhythmias to prevent loratadine toxicity. Loratadine should be stored in a cool, dry place between 68 °F and 77 °F.[4]

Toxicity

Signs and Symptoms of Overdose

Loratadine-induced cardiotoxicity, including cardiac arrhythmias and QT-interval prolongation, is possible in patients, particularly in older patients, who take more than the recommended daily dose. Though rare, overdosing on loratadine may cause significant toxicity, including agitation and symptoms of anticholinergic syndrome. Symptoms include, but are not limited to, mydriasis, urinary retention, tachycardia, and skin flushing.[49][50][51] 

Management of Overdose

Treatment protocol for loratadine toxicity involves supportive care, supplemental oxygen, and cardiac monitoring. Standard ACLS guidelines should be followed. If the patient develops torsades de pointes, loratadine should be discontinued. The management of patients with drug-induced TdP includes identifying and withdrawing the offending drug, replenishing the electrolytes, and infusing intravenous (IV) magnesium. In resistant cases, temporary cardiac pacing may be required to increase the heart rate.[52] The ingestion of 300 mg of loratadine by a child aged 6 resulted in a slight increase in blood pressure and heart rate, which has been managed with supportive care.[53] Adults with symptoms of anticholinergic poisoning due to loratadine toxicity may receive physostigmine antidote therapy (recommended dose is between 0.5 and 2 mg IV). Antidote therapy should be supervised exclusively by a medical toxicologist. There is no evidence of abuse potential or dependency with loratadine.

Enhancing Healthcare Team Outcomes

Loratadine is an effective and safe medication for alleviating symptoms of allergic rhinitis and treating urticaria. The drug is available OTC; therefore, it is essential for pharmacists to educate patients on the therapeutic dose and review their medication profile for potential interactions. The primary care clinician (MD, DO, PA, NP) must counsel the patient on the importance of reading labels to avoid taking more than the recommended dose to reduce the risk of drug-related toxicities. Although loratadine is a relatively safe drug, healthcare providers should inform patients of all potential adverse drug reactions associated with the medication, and medication reconciliation is necessary when adding or discontinuing any drug. A pragmatic trial showed that medication reconciliation, even when done as part of routine clinical practice, significantly reduces the risk of clinically significant medication errors at hospital discharge.[54] 

Healthcare providers should also assess liver and kidney function before prescribing medication to individuals with hepatic or renal impairment. Nurses should take a complete medication history from the patient at each visit, including OTC agents and supplements, and chart these so all interprofessional healthcare team members have comprehensive patient information. Nursing staff can also reinforce counseling to the patient on proper dosing and administration of loratadine, as well as watch for adverse effects and patient compliance. Pharmacists can reinforce dosing and administration parameters and check for drug-drug interactions. In an overdose, emergency physicians should rapidly stabilize the patient. A psychiatric consultation is required if the overdose is intentional.[55] An interprofessional team approach and effective communication among physicians, advanced practice providers, pharmacists, and nurses are crucial to minimizing potential adverse effects and enhancing patient outcomes related to loratadine therapy.

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Disclosure: Preeti Patel declares no relevant financial relationships with ineligible companies.

Disclosure: Hossein Akhondi declares no relevant financial relationships with ineligible companies.