CETIRIZINE HYDROCHLORIDE
Clinical safety rating: safe
No significant drug interactions at recommended doses May cause somnolence although less than first-generation antihistamines.
Selective histamine H1-receptor antagonist; inhibits histamine-mediated allergic and inflammatory responses.
| Metabolism | Minimal hepatic metabolism; primarily excreted unchanged in urine (60%) and feces (10%); a small fraction undergoes oxidative metabolism via CYP3A4. |
| Excretion | Primarily renal (approximately 70% as unchanged drug via glomerular filtration and tubular secretion); minor biliary/fecal elimination (<10%). |
| Half-life | Terminal elimination half-life is approximately 8-11 hours in healthy adults; prolonged in renal impairment (up to 20-30 hours in moderate to severe impairment). |
| Protein binding | 93% bound primarily to albumin. |
| Volume of Distribution | 0.5-0.8 L/kg; distributes into peripheral tissues but limited CNS penetration. |
| Bioavailability | Oral bioavailability is approximately 70% (not significantly affected by food). |
| Onset of Action | Oral: antihistaminic effect begins within 1-2 hours; peak effect at 4-8 hours. |
| Duration of Action | Duration of action is approximately 24 hours for antihistaminic effect; supports once-daily dosing. |
| Molecular Weight | 461.82 |
| Action Class | Second-generation antihistamine (piperazine derivative) |
5-10 mg orally once daily; maximum 10 mg per day.
| Dosage form | SOLUTION |
| Renal impairment | CrCl 30-49 mL/min: 5 mg orally once daily. CrCl 10-29 mL/min: 5 mg orally every other day. CrCl <10 mL/min or hemodialysis: contraindicated. |
| Liver impairment | Child-Pugh A or B: no adjustment required. Child-Pugh C: 5 mg orally once daily due to reduced clearance. |
| Pediatric use | 6-12 months: 2.5 mg orally once daily. 12 months-2 years: 2.5 mg orally once daily, may increase to 2.5 mg twice daily if needed. 2-6 years: 2.5 mg orally once daily, may increase to 2.5 mg twice daily. 6-12 years: 5 mg orally once daily. >12 years: 5-10 mg orally once daily. |
| Geriatric use | Initiate at 5 mg orally once daily; titrate cautiously due to potential renal impairment and increased risk of anticholinergic effects. |
| 1st trimester | Limited human data; animal studies show no evidence of teratogenicity. Use only if clearly needed. |
| 2nd trimester | Considered safe; no known association with congenital malformations. |
| 3rd trimester | Use with caution near term; may cause sedation in neonate or withdrawal symptoms after birth. |
Clinical note
No significant drug interactions at recommended doses May cause somnolence although less than first-generation antihistamines.
| FDA category | Animal |
| Placental transfer | Cetirizine crosses the placenta; extent is unknown but likely low due to moderate molecular weight and protein binding. |
| Breastfeeding |
■ FDA Black Box Warning
None
| Common Effects | urticaria |
| Serious Effects | Anaphylaxis, Angioedema, Severe hypotension, Seizures, Acute generalized exanthematous pustulosis (AGEP), Hepatotoxicity, Thrombocytopenia |
Hypersensitivity to cetirizine or hydroxyzineSevere renal impairment (CrCl <10 mL/min) for oral formulation not recommended
| Precautions | Use with caution in patients with renal impairment (dose adjustment required), Avoid concurrent use with alcohol or CNS depressants, May cause drowsiness; caution when driving or operating machinery |
| Food/Dietary | None significant. Cetirizine absorption is unaffected by food. Avoid concurrent use with alcohol due to additive CNS depression. |
Loading safety data…
| Enters breast milk in low concentrations; unlikely to cause adverse effects in infants. However, use lowest effective dose and monitor for drowsiness, irritability, or feeding difficulties. |
| Lactation Rating | L2 (Limited data - probably compatible) |
| Teratogenic Risk | Cetirizine hydrochloride is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies exist. First trimester: Risk is low based on limited data; no known teratogenicity. Second and third trimesters: Considered safe; however, use only if clearly needed. |
| Fetal Monitoring | No specific routine monitoring required. Observe for maternal adverse effects such as sedation or dry mouth. In neonates exposed near delivery, monitor for potential CNS depression or paradoxical excitation. No fetal monitoring indicated. |
| Fertility Effects | No adverse effects on fertility reported in animal studies. Human data are lacking. Cetirizine is not known to impair fertility in men or women. |
| Clinical Pearls | Cetirizine is a second-generation antihistamine; it is less sedating than first-generation agents but can still cause drowsiness in some patients. Onset of action is within 1 hour; duration is 24 hours. May cause anticholinergic effects (dry mouth, urinary retention) at high doses. Monitor renal function; dose adjustment needed for CrCl <30 mL/min (5 mg daily). Avoid in patients with severe hepatic impairment. Not effective for asthma or anaphylaxis. |
| Patient Advice | Take once daily as directed; may be taken with or without food. · Avoid alcohol and other CNS depressants as they may increase drowsiness. · Report severe drowsiness, confusion, or difficulty urinating to your doctor. · Do not chew or crush the tablet; swallow whole (for tablet form). · May cause dry mouth; use sugar-free gum or candy for relief. · If pregnant or breastfeeding, consult your doctor before use. · Do not exceed recommended dose; overdose may cause severe drowsiness and fast heart rate. |