Long-Term Side Effects of Zyrtec (Cetirizine)
Zyrtec (cetirizine) can cause long-term side effects including somnolence (8%), fatigue (6%), dry mouth, and potential performance impairment, though it generally has a better safety profile than first-generation antihistamines. 1
Common Long-Term Side Effects
Cetirizine is a second-generation antihistamine with a selective H1-receptor antagonist action. While it's generally well-tolerated, several side effects may persist with long-term use:
Neurological Effects
- Somnolence/drowsiness: Affects approximately 8% of patients on long-term therapy 1
- Fatigue: Reported in about 6% of patients 1
- Performance impairment: Can affect driving and cognitive function even without subjective awareness of sedation 1
Other Common Effects
- Dry mouth
- Headache
- Anticholinergic effects (less pronounced than first-generation antihistamines) 1
Special Considerations for Long-Term Use
Drug Interactions
- CNS effects can be enhanced when combined with alcohol or other CNS depressants 1
- Unlike many other antihistamines, cetirizine has low potential for interaction with drugs metabolized by the hepatic cytochrome P450 system 2
Special Populations
- Elderly patients: Increased risk of adverse effects due to decreased renal clearance 1
- Patients with renal impairment: Dosage adjustment required; should be avoided in severe renal impairment 1
- Children: Generally well-tolerated in pediatric patients aged 2-11 years with a similar side effect profile to other second-generation antihistamines 2
Comparative Safety Profile
When comparing long-term safety:
- Cetirizine has a more sedating effect than fexofenadine in some clinical trials 2
- More sedating than loratadine or fexofenadine according to postmarketing surveillance 2
- Unlike some older antihistamines, cetirizine is not associated with cardiotoxicity 2
Important Precautions for Long-Term Users
- Patients should be warned about possible drowsiness and advised to avoid driving or operating machinery until they know how the medication affects them 1
- Avoid alcohol and other CNS depressants while taking cetirizine 1
- Monitor for increased sedation, particularly in elderly patients or those on other sedating medications 1
Clinical Significance
Despite these potential long-term side effects, cetirizine remains an effective option for managing allergic disorders with a favorable benefit-risk profile compared to first-generation antihistamines. Its once-daily dosing regimen may help improve patient compliance with long-term therapy 3.