Combining Claritin (Loratadine) and Hydroxyzine
Yes, it is safe and clinically appropriate to combine Claritin (loratadine) with hydroxyzine, particularly when using loratadine during the day and hydroxyzine at night for conditions like urticaria or allergic rhinitis. 1
Clinical Rationale for Combination Therapy
The British Journal of Dermatology guidelines explicitly support this combination strategy, recommending the addition of a sedating antihistamine like hydroxyzine (10-50 mg) at night to a non-sedating antihistamine during the day for patients with urticaria who have sleep disturbances. 1 This approach leverages the complementary properties of both medications:
- Loratadine provides daytime coverage without sedation or performance impairment at recommended doses 1, 2
- Hydroxyzine at bedtime addresses nighttime symptoms and helps patients sleep better 1
Important Caveats About This Combination
Limited Additional Antihistamine Effect
The guidelines note that adding hydroxyzine at night "probably has little additional clinical effect on urticaria if the H1 receptor is already saturated" by the daytime non-sedating antihistamine. 1 The primary benefit is improved sleep quality rather than enhanced histamine blockade.
Sedation and Performance Concerns
Hydroxyzine causes significant sedation that can persist into the next day despite bedtime dosing. 3, 4 Key safety considerations include:
- Performance impairment can occur without subjective awareness of drowsiness, affecting driving ability and work performance 3
- Drivers taking first-generation antihistamines like hydroxyzine are 1.5 times more likely to be involved in fatal accidents 3
- Even with bedtime dosing, some subjective symptoms (drowsiness, dry mouth, irritability) persist the following day 4
Comparative Safety Profile
Direct comparative studies demonstrate that loratadine and hydroxyzine are clinically comparable in efficacy for urticaria, but loratadine has significantly less sedation and dry mouth compared to hydroxyzine (similar to placebo levels). 5 When both drugs were compared head-to-head:
- Both were significantly more effective than placebo 5
- Sedation with loratadine was comparable to placebo and significantly less than hydroxyzine 5
- Hydroxyzine caused significantly more drowsiness (p=0.001) and dry mouth compared to placebo 6
Special Population Considerations
Renal Impairment
- Hydroxyzine dose should be halved in moderate renal impairment 1
- Loratadine should be used with caution in severe renal impairment 1
Hepatic Impairment
- Hydroxyzine should be avoided in severe liver disease because its sedating effect is inappropriate 1
Pregnancy
- Hydroxyzine is specifically contraindicated during early pregnancy 1, 3
- Loratadine is FDA Pregnancy Category B (no evidence of harm, though well-controlled human studies are lacking) 1
Elderly Patients
- Older adults are more sensitive to psychomotor impairment from hydroxyzine and at increased risk for falls, fractures, and anticholinergic effects 1, 3
- Start with lower doses and monitor closely 3
Practical Dosing Algorithm
For patients requiring combination therapy:
- Loratadine 10 mg once daily in the morning for daytime symptom control without sedation 2, 5
- Hydroxyzine 10-50 mg at bedtime if sleep disturbance is present or additional symptom control is needed 1, 3
- Adjust hydroxyzine dose based on tolerability and renal function 1
Clinical Pearls
- Second-generation antihistamines like loratadine are generally preferred for daytime use due to reduced sedative effects 3
- The combination is most useful when sleep disturbance is a significant problem, not primarily for enhanced antihistamine effect 1
- Warn patients about next-day drowsiness risk even with bedtime hydroxyzine dosing, particularly regarding driving and operating machinery 3, 4
- Consider alternative strategies (increasing loratadine dose, adding H2 antihistamines, or using other second-generation agents) before adding hydroxyzine if sedation is problematic 1