ALLER-TEC (Generic for ZYRTEC)

General Administration Information
For storage information, see the specific product information within the How Supplied section.

Route-Specific Administration

Oral Administration
-The time of cetirizine administration (morning or evening) can be adjusted to meet individual patient needs.
-May be administered without regard to meals.
Oral Solid Formulations
-Capsules: Swallow whole, do not cut, chew, or crush.
-Orally disintegrating tablets: Tablet melts in mouth. May be taken with or without water.
-Chewable tablets: Chew tablet before swallowing. May be taken with or without water.

Oral Liquid Formulations
-Administer using a calibrated measuring device.



Injectable Administration
-Cetirizine injection is for intravenous administration only.
-Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit.
Intravenous Administration
IV Push
-Dilution is not necessary.
-Administer cetirizine injection as an intravenous push over a period of 1 to 2 minutes.
-The vial is for single-use only; discard any unused portion.



Ophthalmic Administration
-Instruct patient on proper instillation of the ophthalmic solution.
-Wash hands before and after use.
-Remove contact lenses prior to instillation of the dose. Contact lenses may be reinserted 10 minutes after the dose has been administered.
-Tilt the head back slightly and pull the lower eyelid down with the index finger to form a pouch. Squeeze 1 drop into the pouch and gently close eyes. Do not blink.
-Take care to avoid contamination. Do not touch the tip of the dropper to the eye, fingertips, or other surface.
-Keep the bottle closed when not in use.

During clinical trials of cetirizine in adults and children 12 years of age and older, the following centrally-mediated effects occurred in at least 2% of patients receiving cetirizine and at an incidence more frequently than with placebo: somnolence/drowsiness (13.7%), fatigue (5.9%), and dizziness (2%). Fatigue and drowsiness were found to be dose-related. The incidence of drowsiness was 11% at a dose of 5 mg/day; with a 10 mg/day dose, the incidence increased to about 14%. In patients 6 to 11 years of age, the following CNS effects occurred more frequently with cetirizine than with placebo: headache (11% to 14%) and drowsiness (1.9% to 4.2%). Adverse effects reported in pediatric patients 2 to 5 years in clinical trials were similar to those reported in older children. CNS effects observed in less than 2% of adult or pediatric patients during clinical trial evaluations of oral cetirizine included abnormal coordination, ataxia, dysphonia, hyperesthesia, hyperkinesis, hypertonia, hypoesthesia, insomnia, migraine, myelitis, paralysis, paresthesias, ptosis, syncope, tremor, twitching, and vertigo. A causal relationship between cetirizine and these infrequent effects has not been established. Paresthesias, headache, and presyncope were reported in less than 1% of patients receiving cetirizine injection. Insomnia (waking up and restlessness) was reported in a 23-month-old child receiving cetirizine 2.5 mg at bedtime for allergic rhinitis; sleep patterns returned to normal within 48 hours of discontinuing the medication. A dystonic reaction was reported in a 6 year-old boy (cetirizine 5 mg/day); he experienced involuntary deviation of the jaw to the left side and inability to swallow. After treatment, all symptoms abated and did not return after discontinuation of cetirizine. During postmarketing use of oral cetirizine, seizures, orofacial dyskinesia, tics, myoclonia, and extrapyramidal symptoms have been reported rarely. The incidence of cetirizine-induced sedation compared with other antihistamines and placebo has been studied. Overall results suggest that cetirizine may be more sedating than fexofenadine, loratadine, terfenadine, or placebo but that the drug is less sedating than older antihistamines. In a clinical trial, patients receiving cetitizine injection reported less sedation at all time points compared to patients treated with diphenhydramine.

During clinical trials of cetirizine in adults and children 12 years of age and older, the following gastrointestinal (GI) effects occurred in at least 2% of patients receiving cetirizine and more frequently than placebo: xerostomia (5% vs. 2.3%). In patients 6 to 11 years of age receiving a dose of 5 mg or 10 mg, the following GI effects occurred more frequently with cetirizine than placebo: abdominal pain (4.4% to 5.6%), diarrhea (1.9% to 3.1%), nausea (1.9% to 2.8%), and vomiting (2.3% to 2.5%). Adverse effects reported in pediatric patients 2 to 5 years of age in clinical trials were similar to those reported in older children. GI effects observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine included aggravated dental caries, anorexia, constipation, dyspepsia, eructation, flatulence, gastritis, hemorrhoids, hypersalivation, appetite stimulation, melena, rectal hemorrhage, stomatitis, ulcerative stomatitis, tongue discoloration, tongue swelling, and weight gain. A causal relationship between cetirizine and these infrequent effects has not been established. Dyspepsia was reported in less than 1% of patients receiving cetirizine injection.

Abnormal hepatic function (unspecified) was observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine; however, a causal relationship to the drug has not been established. In addition, there have been a few reports of transient abnormalities in liver function tests (elevated hepatic enzymes) with use of cetirizine. Most of these events resolved spontaneously. Hepatitis with significant changes in LFTs and hyperbilirubinemia has been reported rarely. Cholestasis has been reported during postmarketing use.

The following dermatologic and/or hypersensitivity effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: acne vulgaris, angioedema, bullous eruption, dermatitis, xerosis, atopic dermatitis, erythematous rash, furunculosis, hyperkeratosis, hypertrichosis, hyperhidrosis, maculopapular rash, photosensitivity, photosensitivity toxic reaction, pruritus, purpura, rash (unspecified), seborrhea, skin disorder (unspecified), skin nodule, and urticaria. A causal relationship between cetirizine and these infrequent effects has not been established. Anaphylactoid reactions have been reported rarely during postmarketing use. Hyperhidrosis was reported in less than 1% of patients receiving cetirizine injection.

During clinical trials of cetirizine in adults and children 12 years of age and older, pharyngitis occurred in 2% of patients receiving cetirizine and 1.9% of patients receiving placebo. In patients 6 to 11 years of age receiving a dose of 5 mg or 10 mg, the following respiratory effects occurred more frequently with cetirizine than placebo: pharyngitis (2.8% to 6.2%), cough (2.8% to 4.4%), bronchospasm (1.9% to 3.1%), and epistaxis (1.9% to 3.7%). Adverse effects reported in pediatric patients 2 to 5 years of age in clinical trials were similar to those reported in children 6 to 11 years. Respiratory effects observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine included bronchitis, dyspnea, hyperventilation, increased sputum, pneumonia, respiratory disorder, rhinitis, sinusitis, and upper respiratory tract infection. A causal relationship between cetirizine and these infrequent effects has not been established.

The following cardiac effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: heart failure, hypertension, palpitations, chest pain (unspecified), and sinus tachycardia. A causal relationship between cetirizine and these infrequent effects has not been established. Severe hypotension has been reported during postmarketing use. In pediatric patients, oral doses of cetirizine 10 mg or less do not increase the QTc interval compared with placebo; doses more than 10 mg/day have not been studied in children for effect on the QTC interval.

The following genitourinary effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: cystitis, dysuria, hematuria, micturition frequency (increased urinary frequency), polyuria, urinary incontinence, urinary tract infection, and urinary retention. A causal relationship between cetirizine and these infrequent effects has not been established. Glomerulonephritis has been reported rarely during postmarketing use.

The following ophthalmic effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of orally administered cetirizine: blindness (visual impairment), conjunctivitis, ocular pain, glaucoma (ocular hypertension), loss of accommodation with blurred vision, ocular hemorrhage, xerophthalmia, and visual field defect. A causal relationship between oral cetirizine and these infrequent effects has not been established. Ocular conjunctival hyperemia, instillation site pain, and visual acuity reduced were reported by 1% to 7% of patients receiving cetirizine ophthalmic solution during clinical trials.

The following otic effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: deafness (hearing loss), earache (otalgia), ototoxicity, and tinnitus. A causal relationship between cetirizine and these infrequent effects has not been established.

The following metabolic effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: dehydration, diabetes mellitus, and thirst (polydipsia). A causal relationship between cetirizine and these infrequent effects has not been established.

The following musculoskeletal effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: arthralgia, arthritis, arthrosis (arthropathy), myasthenia, myalgia, and muscle cramps (leg cramps). A causal relationship between cetirizine and these infrequent effects has not been established.

The following psychiatric effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: abnormal thinking, agitation, amnesia, anxiety, depersonalization, depression, emotional lability, euphoria, impaired concentration, nervousness, paroniria (abnormal dreams or nightmares), and sleep disorder (unspecified). A causal relationship between cetirizine and these infrequent effects has not been established. Aggressive reaction, hallucinations, suicidal ideation, and suicide have been reported rarely during postmarketing use.

The following reproductive effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: dysmenorrhea, female breast pain (mastalgia), intermenstrual bleeding (menstrual irregularity), leukorrhea, menorrhagia, and vaginitis. A causal relationship between cetirizine and these infrequent effects has not been established.

Lymphadenopathy, fever, rigors, and malaise were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine. A causal relationship between cetirizine and these infrequent effects has not been established.

The following special senses effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: parosmia, taste loss, and taste perversion (dysgeusia). A causal relationship between cetirizine and these infrequent effects has not been established. Dysgeusia was reported in less than 1% of patients receiving cetirizine injection.

Flushing was observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine. A causal relationship between cetirizine and this infrequent effect has not been established. Hot flashes have been reported during postmarketing use. Hot flashes were reported in less than 1% of patients receiving cetirizine injection.

Hemolytic anemia and thrombocytopenia have been reported rarely during postmarketing use of cetirizine. Causality to the drug has not been established.

The following general effects were observed in less than 2% of adult or pediatric patients during clinical trial evaluations of cetirizine: accidental injury, asthenia, back pain, enlarged abdomen, face edema, generalized edema, leg edema, nasal polyp, pain (unspecified), periorbital edema, peripheral edema, and pallor. A causal relationship between cetirizine and these infrequent effects has not been established. Stillbirth (fetal death) has been reported rarely during postmarketing use.

Cetirizine is contraindicated for use in patients with a known hypersensitivity to the drug or to any of the formulation components or who have known hydroxyzine hypersensitivity or levocetirizine hypersensitivity. Cetirizine is a known human metabolite of hydroxyzine, and levocetirizine is an enantiomer of cetirizine.

Although cetirizine causes less sedation than first-generation antihistamines, drowsiness has been reported in some patients taking cetirizine in clinical trials. Patients receiving cetirizine should not perform activities requiring coordination and concentration, such as gymnastics, riding a bicycle or for older adolescents, driving or operating machinery, until they are aware of how this medication affects them. Because the effects of alcohol or coadministration with other CNS depressants may be additive with antihistamines, counsel adolescents who could be at risk to avoid ethanol ingestion while taking cetrizine.

In patients with moderate to severe renal impairment (CrCl 31 mL/minute or less) or renal failure, oral cetirizine dosage reduction is recommended. The manufacturer recommends against use in children younger than 6 years of age with any degree of renal impairment due to a lack of data; however, other sources suggest that oral cetirizine can be used at reduced doses in children with a CrCl of at least 10 mL/minute/1.73 m2. No dosage adjustment of cetirizine injection for acute urticaria is required in patients with moderate and severe renal impairment and in patients on dialysis; however, these patients should be monitored for antihistaminic side effects.



Dosage adjustments of oral cetirizine are suggested for patients with hepatic disease as exposure is increased in hepatically impaired patients and the drug clearance rate is reduced. Cetirizine is not recommended for use in children younger than 6 years with hepatic impairment due to a lack of data. No dosage adjustment of intravenous cetirizine is required in patients with hepatic impairment; however these patients should be monitored for antihistaminic side effects.

Use cetirizine with caution in patients with predisposing factors for urinary retention (e.g. spinal cord lesion, urethral stricture). Urinary retention has been reported with cetirizine use and may be exacerbated by the drug.

Instruct patients to remove contact lenses prior to ophthalmic administration of cetirizine. The preservative, benzalkonium chloride, may be absorbed by soft contact lenses. Contact lenses may be reinserted 10 minutes after dose administration; however, advise patients not to wear contact lenses if their eyes are red.

Description: Cetirizine is the active metabolite of hydroxyzine, a piperazine antihistamine or H1-receptor antagonist (H1-blocker). Cetirizine differs from the parent compound by having greater affinity for the H1-receptor. Cetirizine is commercially available as oral, ophthalmic, and injectable formulations. The ophthalmic solution is indicated to treat ocular pruritus associated with allergic conjunctivitis. Oral cetirizine is approved for allergic rhinitis and chronic spontaneous urticaria. In addition, oral cetirizine has been used off-label in pediatric patients for symptomatic treatment of atopic dermatitis. Cetirizine intravenous injection is used to treat acute urticaria. At recommended doses, cetirizine may cause a higher incidence of somnolence than the non-sedating antihistamines (e.g., loratadine), although to a much lesser degree than older antihistamines. Like loratadine, the cardiovascular safety of cetirizine has been demonstrated in drug-interaction studies, elevated-dose studies, and clinical trials. It also appears well-tolerated by pediatric patients. Oral cetirizine is FDA-approved in pediatric patients as young as 6 months. The ophthalmic solution is FDA-approved in pediatric patients as young as 2 years. The injection is FDA-approved in pediatric patients 6 months of age and older.

For the management of symptoms of seasonal allergies or perennial allergies, including allergic rhinitis:
Oral dosage (syrup and solution):
Infants 6 months and older: 2.5 mg PO once daily; prescription use only for perennial allergic rhinitis.
Children under 2 years of age: 2.5 mg PO once daily; prescription use only for perennial allergic rhinitis. If needed, may increase to 2.5 mg every 12 hours.
Children 2 to 5 years: 2.5 mg PO once daily. If needed, may increase to 5 mg PO once daily or 2.5 mg PO twice daily.
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms.
Oral dosage (chewable tablets):
Children 2 to 5 years: Chewable tablets generally not recommended as initial therapy. Initial dose is 2.5 mg PO once daily given as liquid formulation. If needed, the dose may be increased to 5 mg once daily using the chewable tablet.
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms.
Oral dosage (tablets, orally disintegrating tablets, and liquid gels):
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms. Alternatively, 5 mg PO twice daily may better maintain symptom control for some patients. A multicenter double-blind clinical trial was conducted in pediatric patients (6 to 12 years old, n = 124) receiving 5 mg PO twice daily of cetirizine or placebo for allergic rhino-conjunctivitis. Patients receiving cetirizine had more symptom-free or mild symptom days compared to the placebo group (56.2% vs. 29.7%). In clinical trials, most patients older than 12 years started with the 10 mg dose.

For the treatment of symptoms of chronic spontaneous urticaria (e.g., relief of pruritus, reduction in the size and number of hives):
Oral dosage (syrup and solution):
Infants 6 months and older: 2.5 mg PO once daily.
Children under 2 years of age: 2.5 mg PO once daily. If needed, may increase to 2.5 mg every 12 hours.
Children 2 to 5 years: 2.5 mg PO once daily. If needed, may increase to 5 mg PO once daily or 2.5 mg PO twice daily.
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms.
Oral dosage (chewable tablets):
Children 2 to 5 years: Chewable tablets generally not recommended as initial therapy. Initial dose is 2.5 mg PO once daily given as liquid formulation. If needed, the dose may be increased to 5 mg once daily using the chewable tablet.
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms.
Oral dosage (tablets):
Children and Adolescents 6 years and older: 5 to 10 mg PO once daily, depending on severity of symptoms.

For the symptomatic treatment of atopic dermatitis*:
Oral dosage:
Children 1 to 2 years: 0.25 mg/kg/dose PO twice daily.
Children 3 to 5 years: Specific dosing recommendations are not available for children 3 to 5 years old; based on dosing used for allergic rhinitis, consider 2.5 mg PO once daily. May increase to 5 mg once daily or 2.5 mg every 12 hours if needed.
Children 6 to 12 years: 5 to 10 mg PO once daily may be beneficial. In one small study (n = 23), cetirizine 5 mg/day for patients weighing 30 kg or less and 10 mg/day for those weighing more than 30 kg was associated with a more rapid resolution of pruritus, a significant clearing of all atopic dermatitis manifestations, and a significant reduction in the use of concurrent topical medications when compared to placebo.

For the treatment of ocular pruritus associated with allergic conjunctivitis:
Ophthalmic dosage:
Children and Adolescents 2 to 17 years: 1 drop in the affected eye(s) twice daily (approximately 8 hours apart).

For the treatment of acute urticaria:
Intravenous dosage:
Infants 6 months and older: 2.5 mg IV once every 24 hours as needed.
Children 1 to 5 years: 2.5 mg IV once every 24 hours as needed.
Children 6 to 11 years: 5 mg or 10 mg IV (depending on symptom severity) once every 24 hours as needed.
Children and Adolescents 12 years and older: 10 mg IV once every 24 hours as needed.

Maximum Dosage Limits:
-Neonates
Safety and efficacy have not been established.
-Infants
Younger than 6 months: Safety and efficacy have not been established.
6 months and older: 2.5 mg/day PO; 2.5 mg/day IV. Safety and efficacy of ophthalmic solution have not been established.
-Children
1 year: 5 mg/day PO (FDA-approved); 0.25 mg/kg/dose PO twice daily has been used off-label for atopic dermatitis; 2.5 mg/day IV. Safety and efficacy of ophthalmic solution have not been established.
2 years: 5 mg/day PO (FDA-approved); 0.25 mg/kg/dose PO twice daily has been used off-label for atopic dermatitis; 2.5 mg/day IV. 2 drops/day per affected eye for ophthalmic solution.
3 to 5 years: 5 mg/day PO; 2.5 mg/day IV. 2 drops/day per affected eye for ophthalmic solution.
6 years and older: 10 mg/day PO; 10 mg/day IV. 2 drops/day per affected eye for ophthalmic solution.
-Adolescents
10 mg/day PO; 10 mg/day IV. 2 drops/day per affected eye for ophthalmic solution.

Patients with Hepatic Impairment Dosing
Oral Dosage forms
Children less than 6 years: Use is not recommended due to lack of data in hepatically-impaired pediatric patients in this age group.
Children 6 years and older and Adolescents: No more than 5 mg PO once daily.

Intravenous Injection
No dosage adjustment is required in patients with hepatic impairment; however these patients should be monitored for antihistaminic side effects.

Patients with Renal Impairment Dosing
Oral Dosage Forms
FDA-approved recommendations for patients with renal impairment :
Children less than 6 years: Use not recommended due to a lack of data.
Children 6 years and older and Adolescents:
CrCl more than 31 mL/minute: No dosage adjustment needed.
CrCl 31 mL/minute or less: No more than 5 mg PO once daily.

Alternative recommendations for pediatric patients with renal impairment :
CrCl 30 mL/minute/1.73 m2 or more: No dosage adjustment needed.
CrCl 10 to 29 mL/minute/1.73 m2: Administer 50% of the usual dosage.
CrCl less than 10 mL/minute/1.73 m2: Not recommended.

Intravenous Injection
No dosage adjustment is required in patients with moderate and severe renal impairment; however these patients should be monitored for antihistaminic side effects.

Intermittent hemodialysis
Oral Dosage Forms: Follow dosage recommendations as for CrCl 31 mL/minute or less; cetirizine is not removed by hemodialysis.
Intravenous Injection: No dosage adjustment is required.

*non-FDA-approved indication

Monograph content under development

Mechanism of Action: Cetirizine has high affinity for histamine H1-receptors. Unlike cromolyn and nedocromil which block histamine release, H1-antagonists compete with free histamine for binding at H1-receptor sites. In both atopic and normal human volunteers, cetirizine reduction of histamine wheal and flare is similar to that of clemastine, hydroxyzine, and terfenadine. The addition of the less lipophilic carboxyl group to the ethylamine side chain reduces the penetration of cetirizine into the CNS. Consequently, cetirizine produces a low incidence of sedation compared with older antihistamines. Drowsiness may, nevertheless, be dose-related.

In patients with allergic rhinitis, the inflammatory response plays a prominent role in the development of nasal obstruction and involves a number of mediators. Initial release of histamine from mast cells is followed by late-phase reactions involving a number of other cells, such as fibroblasts, epithelial cells, neutrophils, eosinophils (especially in conditions with raised IgE levels), macrophages, platelets, and lymphocytes. Cell adhesion can also be part of the inflammatory process. The action of cetirizine appears to involve a number of these mediators. Cetirizine's effect on mast cells has generated conflicting reports. Some investigators have found that cetirizine decreases prostaglandin D2, while others did not. Similarly, cetirizine may decrease leukotriene C4 production. Cetirizine plays a part in suppressing neutrophil migration in IgE-mediated reactions. Cetirizine reduces eosinophil infiltration to nasal mucosa in patients with seasonal allergic rhinitis. A similar effect is seen in patients with delayed-pressure urticaria. Cetirizine is not believed to affect the immune response, but it might affect cell adhesion. The mechanism of action may involve the inhibition of platelet-activating factor (PAF)-induced influx of eosinophils.

Pharmacokinetics: Cetirizine is administered orally, topically via the ophthalmic route, and as an intravenous injection. It is 93% protein-bound. Cetirizine undergoes a low degree of first-pass metabolism. It is metabolized to limited extent via O-dealkylation to a metabolite with negligible activity; the enzyme(s) responsible for metabolism have not been determined. Overall recovery of an administered dose is roughly 70% in the urine; approximately 50% of a dose is excreted as unchanged drug. Overall recovery from the feces is roughly 10%. The elimination half-life of cetirizine in healthy adult volunteers ranges 6.5 to 10 hours (mean 8.3 hours).

Affected cytochrome P450 (CYP450) isoenzymes and drug transporters: None


-Route-Specific Pharmacokinetics
Oral Route
The oral tablets and oral syrup have comparable bioavailability. Cetirizine is rapidly absorbed from the GI tract with peak plasma concentrations reached approximately 1 hour after administration in adults. The overall bioavailability of cetirizine is not altered by the presence of food, although the rate of absorption can be slightly reduced.

Other Route(s)
Ophthalmic Route
Peak plasma concentrations (Cmax) obtained after administration of cetirizine ophthalmic solution are significantly lower than those achieved by the oral formulations. In a study of healthy subjects, twice daily administration of the ophthalmic solution for 1 week resulted in a Cmax of 3.1 ng/mL. By comparison, the mean Cmax observed in healthy subjects receiving 10 mg tablets once daily for 10 days was 311 ng/mL. The mean terminal half-life was 8.2 hours after twice-daily dosing of ophthalmic cetirizine for 1 week.


-Special Populations
Pediatrics
Infants and Children
Based on cross study comparisons, children exhibit greater weight-normalized apparent body clearances, with a 33% to 63% reduction in elimination half-life when compared to adults. The total body clearance is 33% to 304% greater in pediatric patients than in adults.

Reduction in half-life and increases in total body clearance (CL) in pediatric patients compared to adults :
Infants and Children 6 to 23 months: Half-life = 63% shorter than adults; CL = 304% greater than adults
Children 2 to 5 years: Half-life = 33% to 41% shorter than adults; CL = 81% to 111% greater than adults
Children 7 to 12 years: Half-life = 33% shorter than adults; CL = 33% greater than adults
Note: Pharmacokinetic data in children 6 years of age and adolescents were not included.

Children 4 years and younger
In a pharmacokinetic study, 8 children (29 to 45 months of age) hospitalized with suspected allergic respiratory problems or recurrent respiratory tract infection received a single dose of cetirizine 5 mg PO. The findings were compared to those of healthy young adults who received a single 20 mg dose. Cetirizine was absorbed more slowly in children (1.44 +/- 1.12 hours) than in adults (0.62 +/- 0.22 hours). The half-life of cetirizine was shorter in children (4.91 +/- 0.6 hours) than in adults (8.6 +/- 2.1 hours), and the clearance was faster in children (1.48 +/- 0.41 mL/kg/minute) than in adults (0.8 +/- 0.17 mL/kg/minute). Urinary excretion of unchanged cetirizine was lower in children (37.8% +/- 5.2%; n = 5) than in adults (57.7% +/- 11.8%).

Children 5 years and older
In a pharmacokinetic study, 19 children (5 to 12 years of age) with allergic rhinitis received cetirizine 5 or 10 mg/dose PO once daily for 5 weeks. The following mean pharmacokinetic parameters were calculated for the 5 mg dose: Tmax = 1.4 +/- 1.1 hours, Vd = 0.7 +/- 0.2 L/kg, CL = 1.04 +/- 0.2 mL/kg/minute, and t1/2 = 7.1 +/- 1.6 hours. The following parameters were calculated for the 10 mg dose: Tmax = 0.8 +/- 0.4 hours, Vd = 0.7 +/- 0.1 L/kg, CL = 1.10 +/- 0.13 mL/kg/minute, and t1/2 = 6.9 +/- 1.6 hours.

Hepatic Impairment
Pharmacokinetic parameters of cetirizine have been investigated adult patients with impaired hepatic function. Despite limited hepatic metabolism of cetirizine, patients with chronic liver disease (hepatocellular, cholestatic or biliary cirrhosis) have an altered pharmacokinetic profile, with a 50% increase in half-life along with a corresponding 40% decrease in clearance compared to healthy subjects. The pharmacokinetics of cetirizine in pediatric patients with hepatic impairment have not been studied.

Renal Impairment
Pharmacokinetic parameters of cetirizine have been studied in adult patients with impaired renal function. Adults with renal impairment exhibit a longer time to Cmax, decreased rates of clearance, and an increase in half-life up to 20 hours. Pharmacokinetic parameters in pediatric patients with renal impairment are not known. Hemodialysis removes less than 10% of cetirizine from the blood. Dosing adjustment is necessary in patients with moderate or severe renal impairment (i.e., CrCl 30 mL/minute or less) and in those on dialysis.