Loratadine Clinical Guidelines
Standard Dosing and Administration
Loratadine is dosed at 10 mg once daily for adults and children ≥6 years, and 5 mg once daily for children 2 to under 6 years, with dose adjustments required for patients with liver or kidney disease. 1
Age-Based Dosing
- Adults and children ≥6 years: 10 mg (2 teaspoonfuls) once daily; maximum 10 mg in 24 hours 1
- Children 2 to under 6 years: 5 mg (1 teaspoonful) once daily; maximum 5 mg in 24 hours 1
- Children under 2 years: Consult physician before use 1
Pharmacokinetic Profile
- Onset of action: Within 1 hour, making it suitable for acute allergic reactions 2
- Peak plasma concentration: 1-2 hours for parent drug; 3-4 hours for active metabolite (descarboethoxyloratadine, which is 4 times more potent) 2
- Duration of action: At least 24 hours, supporting once-daily dosing 2
- Elimination half-life: Approximately 10 hours for loratadine; 20 hours for active metabolite 2
Special Populations
Hepatic Impairment
Patients with liver disease must consult a physician before using loratadine, as dose adjustment is necessary. 1 The FDA label specifically flags this population for medical consultation rather than providing specific dosing guidance, reflecting the need for individualized assessment based on severity of hepatic dysfunction 1
Renal Impairment
Patients with kidney disease require physician consultation before initiating loratadine. 1 While the British guidelines note that loratadine should be used with caution in severe renal impairment 3, the FDA label mandates medical evaluation for any degree of renal disease 1
Pregnancy
Loratadine is safe for use during pregnancy, including the first trimester, with large birth registries, case-control studies, and cohort studies confirming no significant increase in congenital malformations. 3
- Second-generation antihistamines like loratadine and cetirizine have been confirmed safe through extensive observational data 3
- Loratadine offers the advantage of less sedation compared to first-generation antihistamines like chlorpheniramine 3
- Critical caveat: Avoid combining loratadine with oral decongestants (phenylephrine, pseudoephedrine) during the first trimester due to associations with gastroschisis and small intestinal atresia 3
- Risk of malformations increases further when decongestants are combined with acetaminophen or salicylates 3
Breastfeeding
While the provided evidence does not contain specific guidance on loratadine use during breastfeeding, the safety profile established during pregnancy and its second-generation antihistamine classification suggest favorable characteristics for lactating women.
Clinical Indications and Efficacy
Allergic Rhinitis
Loratadine is highly effective for allergic rhinitis, with faster onset than astemizole and comparable efficacy to other second-generation antihistamines. 4
- In controlled studies of children aged 3-12 years with dust mite-induced allergic rhinitis, loratadine 5-10 mg daily significantly reduced total symptom scores at day 7 (p=0.003) and day 21 (p=0.06) compared to placebo 5
- Daily symptom scores were significantly lower in all three weeks of treatment (week 1: p=0.014; week 2: p=0.029; week 3: p=0.014) 5
- Loratadine demonstrated superiority to placebo and equivalent efficacy to azatadine, cetirizine, chlorpheniramine, clemastine, hydroxyzine, mequitazine, and terfenadine 4
- In pediatric studies, loratadine 0.11-0.24 mg/kg once daily showed substantial improvement in nasal and ocular symptoms by day 3, maintained throughout 14 days of treatment 6
Chronic Urticaria
Loratadine is as effective as other antihistamines for chronic idiopathic urticaria, with the advantage of once-daily dosing improving adherence. 4
Combination Therapy
For patients with urticaria and sleep disturbances, loratadine 10 mg in the morning can be combined with hydroxyzine 10-50 mg at bedtime. 7
- This AM/PM regimen provides daytime coverage without sedation while addressing nighttime symptoms and sleep disruption 7
- The combination is most useful when sleep disturbance is a significant problem, not primarily for enhanced antihistamine effect 7
- Important contraindication: Hydroxyzine is contraindicated in early pregnancy, so this combination should not be used in pregnant women 3, 7
Safety and Tolerability
Sedation Profile
Loratadine causes significantly less sedation than first-generation antihistamines, with sedation rates comparable to placebo. 4
- Sedation occurred less frequently with loratadine than with azatadine, cetirizine, chlorpheniramine, clemastine, and mequitazine 4
- Loratadine has threefold greater affinity for peripheral versus central histamine H1-receptors, with insignificant amounts entering the brain 2
- In pediatric studies, drowsiness was absent in loratadine-treated children, unlike dexchlorpheniramine-treated controls 6
Cardiovascular Safety
Serious ventricular arrhythmias have not been observed with loratadine, unlike some other second-generation antihistamines. 4 This distinguishes loratadine from terfenadine and astemizole, which have been associated with cardiac complications.
Overdose Experience
A case report of a 6-year-old child who ingested 300 mg loratadine (30 times the standard dose) resulted only in minor elevation of blood pressure and heart rate when managed with supportive care 8. This suggests a wide therapeutic margin, though the minimum toxic dose remains undefined 8.
Common Adverse Events
At standard 10 mg daily dosing, the most commonly reported adverse events are somnolence, fatigue, and headache, occurring at rates similar to placebo 4
Clinical Positioning
First-Line Therapy
Loratadine is an appropriate first-line agent for allergic rhinitis and urticaria due to its once-daily administration, fast onset of action, and essentially non-sedating properties. 4
Comparison with Other Antihistamines
- Versus terfenadine: Comparable therapeutic applications with quicker onset and longer duration of action 2
- Versus astemizole: Loratadine's rapid onset (within 1 hour) makes it more suitable for acute allergic reactions, whereas astemizole requires several days to reach therapeutic effect and is better for prophylactic seasonal allergy treatment 2
- Versus cetirizine: Cetirizine has the shortest time to maximum concentration among second-generation antihistamines, but loratadine offers comparable efficacy with potentially less drowsiness 9, 4
Drug Interaction Potential
Minimal potential for drug interactions exists based on animal data 2, and tachyphylaxis has not been noted in humans 2
Premedication Considerations
When loratadine is used for managing infusion reactions (such as with IV iron), it should be administered as a 10 mg oral dose for treating urticaria. 10 Second-generation antihistamines like loratadine are preferred over first-generation agents (diphenhydramine) for symptom-directed treatment of mild-to-moderate infusion reactions 10
Oral Food Challenge Testing
Loratadine must be discontinued 7 days before oral food challenge testing to avoid interference with interpretation of results. 10 This washout period is longer than many other antihistamines (cetirizine: 5-7 days; fexofenadine: 3 days; diphenhydramine: 3 days) due to loratadine's prolonged duration of action and active metabolite 10