LEVOCETIRIZINE DIHYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Levocetirizine is a selective antagonist of peripheral histamine H1 receptors, blocking histamine-induced allergic responses by inhibiting H1 receptor activation in the gastrointestinal tract, blood vessels, and respiratory tract.
| Metabolism | Levocetirizine undergoes limited hepatic metabolism via CYP450 isoenzymes (primarily CYP3A4) to form an O-glucuronide conjugate; the majority (approximately 85%) is excreted unchanged in urine. |
| Excretion | Renal: 85% as unchanged drug (70%) and metabolites (15%); fecal: 13%; biliary: minimal (<2%). |
| Half-life | Terminal elimination half-life: 7-11 hours in adults. Clinically, this supports once-daily dosing; may be prolonged in renal impairment (creatinine clearance <30 mL/min). |
| Protein binding | Plasma protein binding: 91-92%, primarily to albumin. |
| Volume of Distribution | Vd: 0.3-0.4 L/kg (about 21-28 L in 70 kg adult), indicating distribution predominantly into extracellular fluid. |
| Bioavailability | Oral: approximately 100% (completely absorbed; food does not affect absorption). |
| Onset of Action | Oral: Within 1 hour for symptom relief (peak effect at 2-4 hours). |
| Duration of Action | 24 hours, allowing once-daily dosing. Clinical note: symptom suppression persists for 24 hours in allergic rhinitis and urticaria. |
5 mg orally once daily in the evening.
| Dosage form | TABLET |
| Renal impairment | CrCl 50-79 mL/min: 2.5 mg once daily; CrCl 30-49 mL/min: 2.5 mg every other day; CrCl <30 mL/min or ESRD: contraindicated. |
| Liver impairment | No dosage adjustment required for mild to moderate hepatic impairment. Not studied in severe impairment. |
| Pediatric use | 6-11 years: 2.5 mg orally once daily in the evening; 12 years and older: 5 mg orally once daily in the evening. |
| Geriatric use | No specific adjustment required; however, renal function should be assessed and dosing adjusted based on creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions at recommended doses Rarely may cause somnolence.
| Breastfeeding | Levocetirizine is excreted into human breast milk. The milk-to-plasma (M/P) ratio is approximately 0.3. After a single 5 mg oral dose, the estimated daily infant dose via breast milk is about 0.5-1.3% of the maternal weight-adjusted dose. This is considered low and unlikely to cause adverse effects in a nursing infant. However, caution is advised, particularly in premature infants or those with renal impairment. The American Academy of Pediatrics categorizes cetirizine (the racemic mixture) as compatible with breastfeeding. |
| Teratogenic Risk | Levocetirizine dihydrochloride is classified as FDA Pregnancy Category B. Animal studies in rats and rabbits at doses up to 200 mg/kg/day (approximately 200 and 100 times the maximum recommended human daily oral dose, respectively) revealed no evidence of teratogenicity or embryotoxicity. However, adequate and well-controlled studies in pregnant women are lacking. During the first trimester, the risk of major congenital malformations is not increased based on limited human data. During the second and third trimesters, no specific fetal risks have been identified. However, as with all medications, use during pregnancy should be only if clearly needed. |
■ FDA Black Box Warning
None.
| Common Effects | Rash Nausea Diarrhea Dryness in mouth Fatigue Headache Skin rash Sleepiness Vomiting |
| Serious Effects |
["Hypersensitivity to levocetirizine or any excipients","End-stage renal disease (creatinine clearance <10 mL/min)","Children aged <2 years for PAR/SAR, <6 months for CIU"]
| Precautions | ["Urinary retention: Use with caution in patients with predisposing factors (e.g., spinal cord lesion, prostatic hyperplasia) due to anticholinergic effects","Renal impairment: Dosage adjustment required for creatinine clearance <50 mL/min","CNS effects: May cause drowsiness, fatigue; caution when driving or operating machinery","Not recommended for use in lactating women"] |
Loading safety data…
| Fetal Monitoring | No specific maternal or fetal monitoring is routinely required for levocetirizine use during pregnancy. Standard prenatal care, including ultrasound monitoring for fetal growth if indicated, is sufficient. No increased surveillance for adverse effects is necessary. |
| Fertility Effects | In animal studies, levocetirizine had no effect on fertility in rats at oral doses up to 200 mg/kg/day (approximately 200 times the maximum recommended human daily oral dose). There are no adequate human data on fertility effects. Levocetirizine is not expected to impair fertility in humans. However, as with all antihistamines, caution is advised in men with impaired spermatogenesis due to potential anticholinergic effects, though no evidence exists. |