CATEGORIES: Rhinitis, allergic; Urticaria, chronic idiopathic; Pregnancy Category B; FDA Approved December 1995
Drug Classes: Antihistamines, H1
BRAND NAMES: Zyrtec
FOREIGN BRAND AVAILABILITY:
Alercet (Colombia, Peru);
Alerid (Israel, China);
Cetrine (China, Singapore, Thailand);
Incidal-OD (Indonesia, Thailand);
Razene (New Zealand);
Virlix (France, Italy, Mexico, Philippines, Portugal, Spain);
Zeran (South Africa);
COST OF THERAPY:
For Oral Use.
Cetirizine hydrochloride is an orally active and selective H1-receptor antagonist. The chemical name is (±)-[2-[4-[(4-chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]acetic acid, dihydrochloride. Cetirizine hydrochloride is a racemic compound with an empirical formula of C21H25ClN2O3·2HCl. The molecular weight is 461.82.
Cetirizine hydrochloride is a white, crystalline powder and is water soluble. Zyrtec tablets are formulated as white, film-coated, rounded-off rectangular shaped tablets for oral administration and are available in 5 and 10 mg strengths.
Inactive Ingredients: Lactose, magnesium stearate, povidone, titanium dioxide, hypromellose, polyethylene glycol, and corn starch.
Zyrtec Chewable Tablets
Zyrtec chewable tablets are formulated as purple round tablets for oral administration and are available in 5 and 10 mg strengths.
Inactive Ingredients: Acesulfame potassium, artificial grape flavor, betadex, blue dye, colloidal silicon dioxide, lactose monohydrate, magnesium stearate, mannitol, microcrystalline cellulose, natural flavor, red dye (carmine).
Zyrtec syrup is a colorless to slightly yellow syrup containing cetirizine hydrochloride at a concentration of 1 mg/ml (5 mg/5 ml) for oral administration. The pH is between 4 and 5.
Inactive Ingredients: Banana flavor, glacial acetic acid, glycerin, grape flavor, methylparaben, propylene glycol, propylparaben, sodium acetate, sugar syrup, and water.
Mechanism of Action
Cetirizine, a human metabolite of hydroxyzine, is an antihistamine; its principal effects are mediated via selective inhibition of peripheral H1 receptors. The antihistaminic activity of cetirizine has been clearly documented in a variety of animal and human models. In vivo and ex vivo animal models have shown negligible anticholinergic and antiserotonergic activity. In clinical studies, however, dry mouth was more common with cetirizine than with placebo. In vitro receptor binding studies have shown no measurable affinity for other than H1 receptors. Autoradiographic studies with radiolabeled cetirizine in the rat have shown negligible penetration into the brain. Ex vivo experiments in the mouse have shown that systemically administered cetirizine does not significantly occupy cerebral H1 receptors.
Cetirizine was rapidly absorbed with a time to maximum concentration (Tmax) of approximately 1 hour following oral administration of tablets, chewable tablets, or syrup in adults. Comparable bioavailability was found between the tablet and syrup dosage forms. Comparable bioavailability was also found between the cetirizine HCl tablet and chewable tablet taken with or without water. When healthy volunteers were administered multiple doses of cetirizine (10-mg tablets once daily for 10 days), a mean peak plasma concentration (Cmax) of 311 ng/ml was observed. No accumulation was observed. Cetirizine pharmacokinetics were linear for oral doses ranging from 5-60 mg. Food had no effect on the extent of exposure (AUC) of the cetirizine tablet or chewable tablet, but Tmax was delayed by 1.7 hours and 2.8 hours, respectively, and Cmax was decreased by 23% and 37%, respectively, in the presence of food.
The mean plasma protein binding of cetirizine is 93%, independent of concentration in the range of 25-1000 ng/ml, which includes the therapeutic plasma levels observed.
A mass balance study in 6 healthy male volunteers indicated that 70% of the administered radioactivity was recovered in the urine and 10% in the feces. Approximately 50% of the radioactivity was identified in the urine as unchanged drug. Most of the rapid increase in peak plasma radioactivity was associated with parent drug, suggesting a low degree of first-pass metabolism. Cetirizine is metabolized to a limited extent by oxidative O-dealkylation to a metabolite with negligible antihistaminic activity. The enzyme or enzymes responsible for this metabolism have not been identified.
The mean elimination half-life in 146 healthy volunteers across multiple pharmacokinetic studies was 8.3 hours and the apparent total body clearance for cetirizine was approximately 53 ml/min.
Pharmacokinetic interaction studies with cetirizine in adults were conducted with pseudoephedrine, antipyrine, ketoconazole, erythromycin, and azithromycin. No interactions were observed. In a multiple dose study of theophylline (400 mg once daily for 3 days) and cetirizine (20 mg once daily for 3 days), a 16% decrease in the clearance of cetirizine was observed. The disposition of theophylline was not altered by concomitant cetirizine administration.
When pediatric patients aged 7-12 years received a single, 5-mg oral cetirizine capsule, the mean Cmax was 275 ng/ml. Based on cross-study comparisons, the weight-normalized, apparent total body clearance was 33% greater and the elimination half-life was 33% shorter in this pediatric population than in adults. In pediatric patients aged 2-5 years who received 5 mg of cetirizine, the mean Cmax was 660 ng/ml. Based on cross-study comparisons, the weight-normalized apparent total body clearance was 81-111% greater and the elimination half-life was 33-41% shorter in this pediatric population than in adults. In pediatric patients aged 6-23 months who received a single dose of 0.25 mg/kg cetirizine oral solution (mean dose 2.3 mg), the mean Cmax was 390 ng/ml. Based on cross-study comparisons, the weight-normalized, apparent total body clearance was 304% greater and the elimination half-life was 63% shorter in this pediatric population compared to adults. The average AUC(0-t) in children 6 months to <2 years of age receiving the maximum dose of cetirizine solution (2.5 mg twice a day) is expected to be 2-fold higher than that observed in adults receiving a dose of 10-mg cetirizine tablets once a day.
Following a single, 10-mg oral dose, the elimination half-life was prolonged by 50% and the apparent total body clearance was 40% lower in 16 geriatric subjects with a mean age of 77 years compared to 14 adult subjects with a mean age of 53 years. The decrease in cetirizine clearance in these elderly volunteers may be related to decreased renal function.
A dosing adjustment may be necessary in patients 77 years of age and older (see DOSAGE AND ADMINISTRATION).
Effect of Gender
The effect of gender on cetirizine pharmacokinetics has not been adequately studied.
Effect of Race
No race-related differences in the kinetics of cetirizine have been observed.
The kinetics of cetirizine were studied following multiple, oral, 10-mg daily doses of cetirizine for 7 days in 7 normal volunteers (creatinine clearance 89-128 ml/min), 8 patients with mild renal function impairment (creatinine clearance 42-77 ml/min) and 7 patients with moderate renal function impairment (creatinine clearance 11-31 ml/min). The pharmacokinetics of cetirizine were similar in patients with mild impairment and normal volunteers. Moderately impaired patients had a 3-fold increase in half-life and a 70% decrease in clearance compared to normal volunteers.
Patients on hemodialysis (n=5) given a single, 10-mg dose of cetirizine had a 3-fold increase in half-life and a 70% decrease in clearance compared to normal volunteers. Less than 10% of the administered dose was removed during the single dialysis session.
Dosing adjustment is necessary in patients with moderate or severe renal impairment and in patients on dialysis (see DOSAGE AND ADMINISTRATION).
Sixteen (16) patients with chronic liver diseases (hepatocellular, cholestatic, and biliary cirrhosis), given 10 or 20 mg of cetirizine as a single, oral dose had a 50% increase in half-life along with a corresponding 40% decrease in clearance compared to 16 healthy subjects.
Dosing adjustment may be necessary in patients with hepatic impairment (see DOSAGE AND ADMINISTRATION).
Studies in 69 adult normal volunteers (aged 20-61 years) showed that cetirizine HCl at doses of 5 and 10 mg strongly inhibited the skin wheal and flare caused by the intradermal injection of histamine. The onset of this activity after a single 10-mg dose occurred within 20 minutes in 50% of subjects and within 1 hour in 95% of subjects; this activity persisted for at least 24 hours. Cetirizine HCl at doses of 5 and 10 mg also strongly inhibited the wheal and flare caused by intradermal injection of histamine in 19 pediatric volunteers (aged 5-12 years) and the activity persisted for at least 24 hours. In a 35-day study in children aged 5-12, no tolerance to the antihistaminic (suppression of wheal and flare response) effects of cetirizine HCl was found. In 10 infants 7-25 months of age who received 4-9 days of cetirizine in an oral solution (0.25 mg/kg bid), there was a 90% inhibition of histamine-induced (10 mg/ml) cutaneous wheal and 87% inhibition of the flare 12 hours after administration of the last dose. The clinical relevance of this suppression of histamine-induced wheal and flare response on skin testing is unknown.
The effects of intradermal injection of various other mediators or histamine releasers were also inhibited by cetirizine, as was response to a cold challenge in patients with cold-induced urticaria. In mildly asthmatic subjects, cetirizine HCl at 5-20 mg blocked bronchoconstriction due to nebulized histamine, with virtually total blockade after a 20-mg dose. In studies conducted for up to 12 hours following cutaneous antigen challenge, the late phase recruitment of eosinophils, neutrophils and basophils, components of the allergic inflammatory response, was inhibited by cetirizine HCl at a dose of 20 mg.
In four clinical studies in healthy adult males, no clinically significant mean increases in QTc were observed in cetirizine HCl treated subjects. In the first study, a placebo-controlled crossover trial, cetirizine HCl was given at doses up to 60 mg/day, 6 times the maximum clinical dose, for 1 week, and no significant mean QTc prolongation occurred. In the second study, a crossover trial, cetirizine HCl 20 mg and erythromycin (500 mg every 8 hours) were given alone and in combination. There was no significant effect on QTc with the combination or with cetirizine HCl alone. In the third trial, also a crossover study, cetirizine HCl 20 mg and ketoconazole (400 mg/day) were given alone and in combination. Cetirizine HCl caused a mean increase in QTc of 9.1 msec from baseline after 10 days of therapy. Ketoconazole also increased QTc by 8.3 msec. The combination caused an increase of 17.4 msec, equal to the sum of the individual effects. Thus, there was no significant drug interaction on QTc with the combination of cetirizine HCl and ketoconazole. In the fourth study, a placebo-controlled parallel trial, cetirizine HCl 20 mg was given alone or in combination with azithromycin (500 mg as a single dose on the first day followed by 250 mg once daily). There was no significant increase in QTc with cetirizine HCl 20 mg alone or in combination with azithromycin.
In a 4-week clinical trial in pediatric patients aged 6-11 years, results of randomly obtained ECG measurements before treatment and after 2 weeks of treatment showed that cetirizine HCl 5 or 10 mg did not increase QTc versus placebo. In a 1-week clinical trial (n=86) of cetirizine HCl syrup (0.25 mg/kg bid) compared with placebo in pediatric patients 6-11 months of age, ECG measurements taken within 3 hours of the last dose did not show any ECG abnormalities or increases in QTc interval in either group compared to baseline assessments. Data from other studies where cetirizine HCl was administered to patients 6-23 months of age were consistent with the findings in this study.
The effects of cetirizine HCl on the QTc interval at doses higher than 10 mg have not been studied in children less than 12 years of age.
In a 6-week, placebo-controlled study of 186 patients (aged 12-64 years) with allergic rhinitis and mild to moderate asthma, cetirizine HCl 10 mg once daily improved rhinitis symptoms and did not alter pulmonary function. In a 2-week, placebo-controlled clinical trial, a subset analysis of 65 pediatric (aged 6-11 years) allergic rhinitis patients with asthma showed cetirizine HCl did not alter pulmonary function. These studies support the safety of administering cetirizine HCl to pediatric and adult allergic rhinitis patients with mild to moderate asthma.
Nine multicenter, randomized, double-blind, clinical trials comparing cetirizine 5-20 mg to placebo in patients 12 years and older with seasonal or perennial allergic rhinitis were conducted in the US. Five (5) of these showed significant reductions in symptoms of allergic rhinitis, 3 in seasonal allergic rhinitis (1-4 weeks in duration) and 2 in perennial allergic rhinitis for up to 8 weeks in duration. Two 4-week multicenter, randomized, double-blind, clinical trials comparing cetirizine 5-20 mg to placebo in patients with chronic idiopathic urticaria were also conducted and showed significant improvement in symptoms of chronic idiopathic urticaria. In general, the 10-mg dose was more effective than the 5-mg dose and the 20-mg dose gave no added effect. Some of these trials included pediatric patients aged 12-16 years. In addition, four multicenter, randomized, placebo-controlled, double-blind 2- to 4-week trials in 534 pediatric patients aged 6-11 years with seasonal allergic rhinitis were conducted in the US at doses up to 10 mg.
Seasonal Allergic Rhinitis
Cetirizine HCl is indicated for the relief of symptoms associated with seasonal allergic rhinitis due to allergens such as ragweed, grass and tree pollens in adults and children 2 years of age and older. Symptoms treated effectively include sneezing, rhinorrhea, nasal pruritus, ocular pruritus, tearing, and redness of the eyes.
Perennial Allergic Rhinitis
Cetirizine HCl is indicated for the relief of symptoms associated with perennial allergic rhinitis due to allergens such as dust mites, animal dander and molds in adults and children 6 months of age and older. Symptoms treated effectively include sneezing, rhinorrhea, postnasal discharge, nasal pruritus, ocular pruritus, and tearing.
Cetirizine HCl is indicated for the treatment of the uncomplicated skin manifestations of chronic idiopathic urticaria in adults and children 6 months of age and older. It significantly reduces the occurrence, severity, and duration of hives and significantly reduces pruritus.
Zyrtec is contraindicated in those patients with a known hypersensitivity to it or any of its ingredients or hydroxyzine.
Activities Requiring Mental Alertness
In clinical trials, the occurrence of somnolence has been reported in some patients taking cetirizine HCl; due caution should therefore be exercised when driving a car or operating potentially dangerous machinery. Concurrent use of cetirizine HCl with alcohol or other CNS depressants should be avoided because additional reductions in alertness and additional impairment of CNS performance may occur.
Carcinogenesis, Mutagenesis, and Impairment of Fertility
In a 2-year carcinogenicity study in rats, cetirizine was not carcinogenic at dietary doses up to 20 mg/kg (approximately 15 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately 7 times the maximum recommended daily oral dose in infants on a mg/m2 basis). In a 2-year carcinogenicity study in mice, cetirizine caused an increased incidence of benign liver tumors in males at a dietary dose of 16 mg/kg (approximately 6 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately 3 times the maximum recommended daily oral dose in infants on a mg/m2 basis). No increase in the incidence of liver tumors was observed in mice at a dietary dose of 4 mg/kg (approximately 2 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately equivalent to the maximum recommended daily oral dose in infants on a mg/m2 basis). The clinical significance of these findings during long-term use of cetirizine HCl is not known.
Cetirizine was not mutagenic in the Ames test, and not clastogenic in the human lymphocyte assay, the mouse lymphoma assay, and in vivo micronucleus test in rats.
In a fertility and general reproductive performance study in mice, cetirizine did not impair fertility at an oral dose of 64 mg/kg (approximately 25 times the maximum recommended daily oral dose in adults on a mg/m2 basis).
Pregnancy Category B
In mice, rats, and rabbits, cetirizine was not teratogenic at oral doses up to 96, 225, and 135 mg/kg, respectively (approximately 40, 180, and 220 times the maximum recommended daily oral dose in adults on a mg/m2 basis). There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, cetirizine HCl should be used during pregnancy only if clearly needed.
In mice, cetirizine caused retarded pup weight gain during lactation at an oral dose in dams of 96 mg/kg (approximately 40 times the maximum recommended daily oral dose in adults on a mg/m2 basis). Studies in beagle dogs indicated that approximately 3% of the dose was excreted in milk. Cetirizine has been reported to be excreted in human breast milk. Because many drugs are excreted in human milk, use of cetirizine HCl in nursing mothers is not recommended.
Of the total number of patients in clinical studies of cetirizine HCl, 186 patients were 65 years and older, and 39 patients were 75 years and older. No overall differences in safety were observed between these patients and younger patients, but greater sensitivity of some older individuals cannot be ruled out. With regard to efficacy, clinical studies of cetirizine HCl for each approved indication did not include sufficient numbers of patients aged 65 years and older to determine whether they respond differently than younger patients.
Cetirizine HCl is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function. (See CLINICAL PHARMACOLOGY, Special Populations: Geriatric Patients and Renal Impairment.)
The safety of cetirizine HCl has been demonstrated in pediatric patients aged 6 months to 11 years. The safety of cetirizine HCl, at daily doses of 5 or 10 mg, has been demonstrated in 376 pediatric patients aged 6-11 years in placebo-controlled trials lasting up to 4 weeks and in 254 patients in a non-placebo-controlled 12-week trial. The safety of cetirizine has been demonstrated in 168 patients aged 2-5 years in placebo-controlled trials of up to 4 weeks duration. On a mg/kg basis, most of the 168 patients received between 0.2 and 0.4 mg/kg of cetirizine HCl. The safety of cetirizine in 399 patients aged 12-24 months has been demonstrated in a placebo-controlled 18-month trial, in which the average dose was 0.25 mg/kg bid, corresponding to a range of 4-11 mg/day. The safety of cetirizine HCl syrup has been demonstrated in 42 patients aged 6-11 months in a placebo-controlled 7-day trial. The prescribed dose was 0.25 mg/kg bid, which corresponded to a mean of 4.5 mg/day, with a range of 3.4-6.2 mg/day.
The effectiveness of cetirizine HCl for the treatment of allergic rhinitis and chronic idiopathic urticaria in pediatric patients aged 6 months to 11 years is based on an extrapolation of the demonstrated efficacy of cetirizine HCl in adults with these conditions and the likelihood that the disease course, pathophysiology and the drug's effect are substantially similar between these two populations. Efficacy is extrapolated down to 6 months of age for perennial allergic rhinitis and down to 2 years of age for seasonal allergic rhinitis because these diseases are thought to occur down to these ages in children. The recommended doses for the pediatric population are based on cross-study comparisons of the pharmacokinetics and pharmacodynamics of cetirizine in adult and pediatric subjects and on the safety profile of cetirizine in both adult and pediatric patients at doses equal to or higher than the recommended doses. The cetirizine AUC and Cmax in pediatric subjects aged 6-23 months who received a mean of 2.3 mg in a single dose and in subjects aged 2-5 years who received a single dose of 5 mg of cetirizine syrup and in pediatric subjects aged 6-11 years who received a single dose of 10 mg of cetirizine syrup were estimated to be intermediate between that observed in adults who received a single dose of 10 mg of cetirizine tablets and those who received a single dose of 20 mg of cetirizine tablets.
The safety and effectiveness of cetirizine in pediatric patients under the age of 6 months have not been established.
No clinically significant drug interactions have been found with theophylline at a low dose, azithromycin, pseudoephedrine, ketoconazole, or erythromycin. There was a small decrease in the clearance of cetirizine caused by a 400-mg dose of theophylline; it is possible that larger theophylline doses could have a greater effect.
Controlled and uncontrolled clinical trials conducted in the US and Canada included more than 6000 patients aged 12 years and older, with more than 3900 receiving cetirizine HCl at doses of 5-20 mg/day. The duration of treatment ranged from 1 week to 6 months, with a mean exposure of 30 days.
Most adverse reactions reported during therapy with cetirizine HCl were mild or moderate. In placebo-controlled trials, the incidence of discontinuations due to adverse reactions in patients receiving cetirizine HCl 5 or 10 mg was not significantly different from placebo (2.9% vs 2.4%, respectively).
The most common adverse reaction in patients aged 12 years and older that occurred more frequently on cetirizine HCl than placebo was somnolence. The incidence of somnolence associated with cetirizine HCl was dose related, 6% in placebo, 11% at 5 mg and 14% at 10 mg. Discontinuations due to somnolence for cetirizine HCl were uncommon (1.0% on cetirizine HCl vs 0.6% on placebo). Fatigue and dry mouth also appeared to be treatment-related adverse reactions. There were no differences by age, race, gender, or by body weight with regard to the incidence of adverse reactions.
TABLE 1 lists adverse experiences in patients aged 12 years and older which were reported for cetirizine HCl 5 and 10 mg in controlled clinical trials in the US and that were more common with cetirizine HCl than placebo.
In addition, headache and nausea occurred in more than 2% of the patients, but were more common in placebo patients.
Pediatric studies were also conducted with cetirizine HCl. More than 1300 pediatric patients aged 6-11 years with more than 900 treated with cetirizine HCl at doses of 1.25-10 mg/day were included in controlled and uncontrolled clinical trials conducted in the US. The duration of treatment ranged from 2-12 weeks. Placebo-controlled trials up to 4 weeks duration included 168 pediatric patients aged 2-5 years who received cetirizine, the majority of whom received single daily doses of 5 mg. A placebo-controlled trial 18 months in duration included 399 patients aged 12-24 months treated with cetirizine (0.25 mg/kg bid), and another placebo-controlled trial of 7 days duration included 42 patients aged 6-11 months who were treated with cetirizine (0.25 mg/kg bid).
The majority of adverse reactions reported in pediatric patients aged 2-11 years with cetirizine HCl were mild or moderate. In placebo-controlled trials, the incidence of discontinuations due to adverse reactions in pediatric patients receiving up to 10 mg of cetirizine HCl was uncommon (0.4% on cetirizine HCl vs 1.0% on placebo).
TABLE 2 lists adverse experiences which were reported for cetirizine HCl 5 and 10 mg in pediatric patients aged 6-11 years in placebo-controlled clinical trials in the US and were more common with cetirizine HCl than placebo. Of these, abdominal pain was considered treatment-related and somnolence appeared to be dose-related, 1.3% in placebo, 1.9% at 5 mg, and 4.2% at 10 mg. The adverse experiences reported in pediatric patients aged 2-5 years in placebo-controlled trials were qualitatively similar in nature and generally similar in frequency to those reported in trials with children aged 6-11 years.
In the placebo-controlled trials of pediatric patients 6-24 months of age, the incidences of adverse experiences were similar in the cetirizine and placebo treatment groups in each study. Somnolence occurred with essentially the same frequency in patients who received cetirizine and patients who received placebo. In a study of 1 week duration in children 6-11 months of age, patients who received cetirizine exhibited greater irritability/fussiness than patients on placebo. In a study of 18 months duration in patients 12 months and older, insomnia occurred more frequently in patients who received cetirizine compared to patients who received placebo (9.0% vs 5.3%). In those patients who received 5 mg or more per day of cetirizine as compared to patients who received placebo, fatigue (3.6% vs 1.3%) and malaise (3.6% vs 1.8%) occurred more frequently.
The following events were observed infrequently (less than 2%), in either 3982 adults and children 12 years and older or in 659 pediatric patients aged 6-11 years who received cetirizine HCl in US trials, including an open adult study of 6 months duration. A causal relationship of these infrequent events with cetirizine HCl administration has not been established.
Occasional instances of transient, reversible hepatic transaminase elevations have occurred during cetirizine therapy. Hepatitis with significant transaminase elevation and elevated bilirubin in association with the use of cetirizine HCl has been reported.
In the postmarketing period, the following additional rare, but potentially severe adverse events have been reported: aggressive reaction, anaphylaxis, cholestasis, convulsions, glomerulonephritis, hallucinations, hemolytic anemia, hepatitis, orofacial dyskinesia, severe hypotension, stillbirth, suicidal ideation, suicide and thrombocytopenia.
There is no information to indicate that abuse or dependency occurs with cetirizine HCl.
Overdosage has been reported with cetirizine HCl. In 1 adult patient who took 150 mg of cetirizine HCl, the patient was somnolent but did not display any other clinical signs or abnormal blood chemistry or hematology results. In an 18-month-old pediatric patient who took an overdose of cetirizine HCl (approximately 180 mg), restlessness and irritability were observed initially; this was followed by drowsiness. Should overdose occur, treatment should be symptomatic or supportive, taking into account any concomitantly ingested medications. There is no known specific antidote to cetirizine HCl. Cetirizine HCl is not effectively removed by dialysis, and dialysis will be ineffective unless a dialyzable agent has been concomitantly ingested. The acute minimal lethal oral doses were 237 mg/kg in mice (approximately 95 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately 40 times the maximum recommended daily oral dose in infants on a mg/m2 basis) and 562 mg/kg in rats (approximately 460 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately 190 times the maximum recommended daily oral dose in infants on a mg/m2 basis). In rodents, the target of acute toxicity was the central nervous system, and the target of multiple-dose toxicity was the liver.
Cetirizine HCl can be taken without regard to food consumption. Cetirizine HCl is available as 5- and 10-mg tablets, 1 mg/ml syrup, and 5- and 10-mg chewable tablets which can be taken with or without water.
Adults and Children 12 Years and Older
The recommended initial dose of cetirizine HCl is 5 or 10 mg/day in adults and children 12 years and older, depending on symptom severity. Most patients in clinical trials started at 10 mg. Cetirizine HCl is given as a single daily dose. The time of administration may be varied to suit individual patient needs.
Children 6-11 Years
The recommended initial dose of cetirizine HCl in children aged 6-11 years is 5 or 10 mg once daily depending on symptom severity. The time of administration may be varied to suit individual patient needs.
Children 2-5 Years
The recommended initial dose of cetirizine HCl in children aged 2-5 years is 2.5 mg (½ teaspoon) syrup once daily. The dosage in this age group can be increased to a maximum dose of 5 mg/day given as 1 teaspoon once a day or one ½ teaspoon syrup given every 12 hours, or one 5-mg chewable tablet once a day.
Children 6 Months to <2 Years
The recommended dose of cetirizine HCl syrup in children 6-23 months of age is 2.5 mg (½ teaspoon) once daily. The dose in children 12-23 months of age can be increased to a maximum dose of 5 mg/day, given as ½ teaspoon (2.5 mg) every 12 hours. Syrup is recommended for children under the age of 2 years.
Dose Adjustment for Renal and Hepatic Impairment
In patients 12 years of age and older with decreased renal function (creatinine clearance 11-31 ml/min), patients on hemodialysis (creatinine clearance less than 7 ml/min), and in hepatically impaired patients, a dose of 5 mg once daily is recommended. Similarly, pediatric patients aged 6-11 years with impaired renal or hepatic function should use the lower recommended dose. Because of the difficulty in reliably administering doses of less than 2.5 mg (½ teaspoon) of cetirizine HCl syrup and in the absence of pharmacokinetic and safety information for cetirizine in children below the age of 6 years with impaired renal or hepatic function, its use in this impaired patient population is not recommended.
Dose Adjustment for Geriatric Patients
In patients 77 years of age and older, a dose of 5 mg once daily is recommended.
Storage: Store at 20-25°C (68-77°F); excursions permitted to 15-30°C (59-86°F).
Zyrtec Chewable Tablets
Storage: Store at 20-25°C (68-77°F); excursions permitted to 15-30°C (59-86°F).
Zyrtec syrup is colorless to slightly yellow with a banana-grape flavor. Each teaspoon (5 ml) contains 5 mg cetirizine HCl.
Storage: Store at 20-25°C (68-77°F); excursions permitted to 15-30°C (59-86°F); or store refrigerated, 2-8°C (36-46°F).