LORATADINE
Clinical safety rating: safe
No significant drug interactions at recommended doses Rarely may cause headache or somnolence.
Loratadine is a long-acting tricyclic antihistamine with selective peripheral H1-receptor antagonist activity. It inhibits histamine-induced vasodilation and bronchoconstriction.
| Metabolism | Loratadine is extensively metabolized in the liver via CYP3A4 and to a lesser extent CYP2D6 to its active metabolite desloratadine. |
| Excretion | Approximately 40% excreted in urine as metabolites (primarily descarboethoxyloratadine) and 40% in feces as metabolites; <1% excreted unchanged. |
| Half-life | Loratadine: 8-14 hours (mean ~10 hours). Active metabolite descarboethoxyloratadine: 17-24 hours (mean ~20 hours). Clinically, duration supports once-daily dosing. |
| Protein binding | Loratadine: 97-99% bound to plasma proteins (albumin and alpha-1-acid glycoprotein). Metabolite: 73-76% bound. |
| Volume of Distribution | Approximately 119 L/kg (range 80-150 L/kg). High Vd indicates extensive tissue distribution, likely due to lipophilicity. |
| Bioavailability | Oral bioavailability is high but variable; absolute bioavailability ~70-90% (first-pass metabolism limited). |
| Onset of Action | Oral: 1-3 hours (symptom relief begins). Peak effect at 2-4 hours. |
| Duration of Action | >24 hours for symptomatic control of allergic rhinitis. Duration allows once-daily dosing. |
| Molecular Weight | 382.88 |
| Action Class | Second-generation antihistamine (piperidine class) |
10 mg orally once daily
| Dosage form | TABLET |
| Renal impairment | No adjustment required for GFR ≥10 mL/min; avoid use in patients with GFR <10 mL/min due to lack of data |
| Liver impairment | Child-Pugh Class A: 10 mg orally once daily; Child-Pugh Class B or C: 10 mg orally every other day |
| Pediatric use | 2-5 years: 5 mg orally once daily; 6 years and older: 10 mg orally once daily |
| Geriatric use | No specific dose adjustment; use with caution due to potential age-related renal impairment |
| 1st trimester | Limited human data; animal studies show no teratogenic effects at clinically relevant doses. Generally considered low risk, but use only if clearly needed. |
| 2nd trimester | No known fetal risk; preferred antihistamine in pregnancy due to safety profile. |
| 3rd trimester | No known risk; can be used near term as needed. |
Clinical note
No significant drug interactions at recommended doses Rarely may cause headache or somnolence.
| FDA category | Animal |
| Placental transfer | Placental transfer occurs; data suggest limited transfer to fetus, but exact extent not well defined. |
| Breastfeeding | Excreted into breast milk in low amounts (approx. 0.029% of maternal dose). Not expected to cause adverse effects in infants. Monitor for irritability or drowsiness. |
■ FDA Black Box Warning
None.
| Common Effects | urticaria |
| Serious Effects | Anaphylaxis, Angioedema, Hepatotoxicity, Seizures, Cardiac arrhythmias (rare, primarily with overdose) |
Hypersensitivity to loratadine or any component of formulation
| Precautions | Use with caution in patients with severe hepatic impairment (dose reduction recommended), May cause drowsiness in some patients; avoid driving or operating machinery if affected, Avoid use in patients with history of hypersensitivity to loratadine or any component, Concomitant use with CYP3A4 or CYP2D6 inhibitors may increase loratadine levels |
| Food/Dietary | No significant food interactions. Loratadine absorption is not affected by food. Grapefruit juice may slightly decrease the active metabolite concentration but this is not clinically significant. Avoid high-fat meals if using the rapidly disintegrating tablet (ODT) as it may reduce absorption. No restriction on alcohol, but caution due to potential additive CNS effects. |
Loading safety data…
| Lactation Rating | L1 |
| Teratogenic Risk | Loratadine is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and adequate well-controlled studies in pregnant women are lacking. First trimester: no evidence of teratogenicity in epidemiologic studies; second and third trimesters: no known fetal risks. |
| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for maternal adverse effects such as sedation (rare) and potential antihistamine effects. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies have not shown impaired fertility. |
| Clinical Pearls | Loratadine is a second-generation antihistamine with minimal anticholinergic and sedative effects due to its limited CNS penetration. It is a prodrug that is rapidly converted to its active metabolite desloratadine. Onset of action is within 1-3 hours, and duration is approximately 24 hours. Dose adjustment is recommended for patients with severe hepatic impairment (e.g., Child-Pugh score >10) or renal impairment (CrCl <30 mL/min) with a starting dose of 10 mg every other day. It does not interact significantly with CYP3A4 inhibitors like ketoconazole or erythromycin, unlike many other antihistamines. For chronic urticaria, it is first-line therapy. It may be less effective for nasal congestion compared to intranasal corticosteroids. |
| Patient Advice | Take one 10 mg tablet or 10 mg oral solution once daily with or without food. · Do not exceed 10 mg in 24 hours; do not take more than directed. · Avoid alcohol consumption as it may increase drowsiness, though loratadine is less sedating than older antihistamines. · If you have severe liver or kidney disease, consult your doctor for dose adjustment. · Store at room temperature away from moisture and heat. · Do not use for rapid relief of acute allergic reactions; seek emergency care for breathing difficulty or throat swelling. · If you miss a dose, skip it and take the next dose at the regular time. Do not double the dose. · Pregnant or breastfeeding patients should consult a healthcare provider before use. · Loratadine may cause dry mouth; sugar-free gum or candy can help. · Children under 2 years of age: do not use without physician advice. · Antihistamines can cause allergic skin rashes rarely; stop use and seek medical attention if you develop hives or swelling. |