[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) › Loratadine # Loratadine ## H1 antihistamines? H1 antihistamines A once-daily second-generation antihistamine for hay fever and allergic itch that rarely causes drowsiness. Updated Nov 1, 2026 ## Quick facts **Group** [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) **Target** Histamine H1 receptor **Used for** Allergic rhinitis · Itchy · Hives **Key effects** Headache · Mild drowsiness or tiredness · Dry mouth **Monitor** Symptom relief · Drowsiness in sensitive patients **ATC** R06AX13 No doses: the clinician sets them by the current guideline. On this page - The basics Mechanism of action - Indications - Adverse effects - Pharmacokinetics - Memory aid - Safety Contraindications - Key interactions - What is monitored - Administration and safety - Pregnancy and breastfeeding - Nursing care - Study Test yourself - Connections Connections ## Mechanism of action ◎**Histamine H1 receptor**Loratadine ⓘ The figure shows desloratadine bound to the human histamine H1 receptor (cryo-electron microscopy); desloratadine is the active metabolite of loratadine. **Target in 3D:** Histamine H1 receptor. PDB structure 8X64 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8X64) · Drag to rotate · pinch to zoom Loratadine is a long-acting second-generation H1 antihistamine. It and its active metabolite desloratadine act as inverse agonists at peripheral H1 receptors, blocking histamine-driven sneezing, itching, runny nose, watery eyes and wheals. Because it is poorly able to cross the blood–brain barrier, it has little sedative or anticholinergic effect at usual doses. - Loratadine is absorbed and converted in the liver to desloratadine - Both bind peripheral H1 receptors and keep them inactive - Histamine can no longer cause itch, sneezing and leaky vessels - Little reaches the brain, so sedation is rare ## Indications - Allergic rhinitis (sneezing, runny and itchy nose) [Allergic rhinitis →](https://durgical.com/en/conditions/allergic-rhinitis/) - Itchy, watery eyes of allergic conjunctivitis [Conjunctivitis →](https://durgical.com/en/conditions/conjunctivitis/) - Hives (urticaria) [Urticaria and angioedema →](https://durgical.com/en/conditions/urticaria-and-angioedema/) ## Adverse effects ### Common - Headache - Mild drowsiness or tiredness in some people - Dry mouth ### Serious (rare, important) - Allergic reactions to the drug (rash, swelling, difficulty breathing): rare ## Contraindications - Hypersensitivity to loratadine or desloratadine - Caution in significant liver or kidney disease ## Key interactions **Desloratadine and other H1 antihistamines** Duplicate H1 blockade (desloratadine is the same active substance): not combined **Alcohol, benzodiazepines, opioids and other CNS depressants** Additive sedation and slowed breathing ## What is monitored - Symptom relief - Drowsiness in sensitive patients ## Administration and safety - Oral tablets, orally disintegrating tablets or syrup, once a day - Combination products with pseudoephedrine exist: check the label so the decongestant is not taken by someone who should avoid it ## Pregnancy and breastfeeding Loratadine is one of the antihistamines with the most pregnancy experience; whether to use it is decided with the clinician. ## Nursing care - Ask about allergy triggers and other antihistamines or cold products already used - Explain that it does not replace epinephrine in a severe allergic reaction - Teach that drowsiness is uncommon but possible ## Pharmacokinetics **Absorption** Well absorbed by mouth **Metabolism** Extensive first-pass metabolism in the liver (CYP3A4, CYP2D6) to the active metabolite desloratadine **Elimination** As metabolites in urine and faeces **Onset and duration** Relief within hours, lasting about a day ## Memory aid LORatadine: LOng-acting, Rarely sedating, once a day. ## Test yourself Think of the answer, then tap the question to see it. ## What is the active metabolite of loratadine? Desloratadine. ## Why does loratadine cause less sedation than diphenhydramine? It crosses the blood–brain barrier poorly, so it blocks few central H1 receptors. ## A patient with anaphylaxis has taken loratadine. Is that enough treatment? No; intramuscular epinephrine is the first treatment, antihistamines only help the skin symptoms. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/loratadine/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Connections ## Related drugs 3 - [Desloratadine](https://durgical.com/en/pharmacology/desloratadine/) - [Cetirizine](https://durgical.com/en/pharmacology/cetirizine/) - [Fexofenadine](https://durgical.com/en/pharmacology/fexofenadine/) ## Related conditions 3 - [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/) - [Conjunctivitis](https://durgical.com/en/conditions/conjunctivitis/) - [Urticaria and angioedema](https://durgical.com/en/conditions/urticaria-and-angioedema/) [← Back to the class: H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Loratadine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a697038.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - DESLORATADINE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2a90b899-7746-43dc-ac8a-e754428eb30c) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=R06AX13) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=loratadine) (World Health Organization, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/loratadine/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/loratadine/