No, you should not take loratadine twice in one day
The FDA-approved dosing for loratadine is 10 mg once daily for adults and children 6 years and older, and you should not exceed this dose in a 24-hour period 1. Taking more than the recommended dose may cause drowsiness 1.
Why Once-Daily Dosing is Standard
Loratadine is a second-generation antihistamine specifically designed for once-daily administration. The evidence supporting this dosing includes:
Guideline recommendations: Loratadine does not cause sedation at recommended doses, but may cause sedation at doses exceeding the recommended dose 2. This is a critical safety consideration that distinguishes it from fexofenadine, which maintains its non-sedating profile even at higher doses.
Clinical efficacy: Multiple studies demonstrate that loratadine 10 mg once daily is effective for both seasonal and perennial allergic rhinitis, with maintained efficacy throughout 14-28 day treatment courses 3, 4. There is no evidence that twice-daily dosing improves outcomes.
Pharmacokinetic profile: The drug is formulated for 24-hour coverage with a single dose, making additional doses unnecessary for symptom control.
Important Safety Considerations
Sedation Risk with Higher Doses
While loratadine is marketed as "non-sedating," this property only holds true at the recommended 10 mg daily dose. Exceeding the recommended dose introduces sedation risk that you may not subjectively perceive, yet can still impair your performance 2.
Special Populations
If you have liver or kidney disease, consult your doctor before taking loratadine, as you may need a different (likely lower) dose 1. Patients with low body mass may also be at higher risk for drowsiness and performance impairment even at standard doses 2.
What to Do If Symptoms Persist
If once-daily loratadine isn't adequately controlling your symptoms, do not simply double the dose. Instead, consider these evidence-based alternatives:
Switch to an intranasal antihistamine (azelastine or olopatadine), which are more effective than oral antihistamines for nasal symptoms, particularly congestion, and have rapid onset of action 5
Add or switch to an intranasal corticosteroid, which represents the most effective monotherapy for allergic rhinitis 2
Consult your healthcare provider about updosing strategies that are evidence-based (some guidelines support updosing certain antihistamines up to 4-fold for chronic urticaria, but this requires medical supervision)
Bottom Line
Stick to the once-daily dosing. The FDA labeling is clear: do not take more than 2 teaspoonfuls (10 mg) in 24 hours 1. If your symptoms require more aggressive management, the solution is switching to a more effective medication class or combination therapy, not exceeding the recommended loratadine dose.