5.1 Paradoxical Bronchospasm

Levalbuterol Inhalation Solution, USP can produce paradoxical bronchospasm, which may be life-threatening. If paradoxical bronchospasm occurs, Levalbuterol Inhalation Solution, USP should be discontinued immediately and alternative therapy instituted. It should be recognized that paradoxical bronchospasm, when associated with inhaled formulations, frequently occurs with the first use of a new vial.

5.2 Deterioration of Asthma

Asthma may deteriorate acutely over a period of hours or chronically over several days or longer. If the patient needs more doses of Levalbuterol Inhalation Solution, USP than usual, this may be a marker of destabilization of asthma and requires reevaluation of the patient and treatment regimen, giving special consideration to the possible need for anti-inflammatory treatment, e.g., corticosteroids.

5.3 Use of Anti-Inflammatory Agents

Levalbuterol Inhalation Solution, USP is not a substitute for corticosteroids. The use of beta-adrenergic agonist alone may not be adequate to control asthma in many patients. Early consideration should be given to adding anti-inflammatory agents, e.g., corticosteroids, to the therapeutic regimen.

5.4 Cardiovascular Effects

Levalbuterol Inhalation Solution, USP, like other beta-adrenergic agonists, can produce clinically significant cardiovascular effects in some patients, as measured by heart rate, blood pressure, and symptoms. Although such effects are uncommon after administration of Levalbuterol Inhalation Solution, USP at recommended doses, if they occur, the drug may need to be discontinued. In addition, beta-agonists have been reported to produce electrocardiogram (ECG) changes, such as flattening of the t-wave, prolongation of the QTc interval, and ST segment depression. The clinical significance of these findings is unknown. Therefore, Levalbuterol Inhalation Solution, USP, like all sympathomimetic amines, should be used with caution in patients with cardiovascular disorders, especially coronary insufficiency, cardiac arrhythmias, and hypertension.

5.5 Do Not Exceed Recommended Dose

Do not exceed the recommended dose. Fatalities have been reported in association with excessive use of inhaled sympathomimetic drugs in patients with asthma. The exact cause of death is unknown, but cardiac arrest following an unexpected development of a severe acute asthmatic crisis and subsequent hypoxia is suspected.

5.6 Immediate Hypersensitivity Reactions

Immediate hypersensitivity reactions may occur after administration of levalbuterol or racemic albuterol. Reactions have included urticaria, angioedema, rash, bronchospasm, anaphylaxis, and oropharyngeal edema. The potential for hypersensitivity must be considered in the clinical evaluation of patients who experience immediate hypersensitivity reactions while receiving Levalbuterol Inhalation Solution, USP.

5.7 Coexisting Conditions

Levalbuterol Inhalation Solution, USP, like all sympathomimetic amines, should be used with caution in patients with cardiovascular disorders, especially coronary insufficiency, hypertension, and cardiac arrhythmias; in patients with convulsive disorders, hyperthyroidism, or diabetes mellitus; and in patients who are unusually responsive to sympathomimetic amines. Clinically significant changes in systolic and diastolic blood pressure have been seen in individual patients and could be expected to occur in some patients after the use of any beta-adrenergic bronchodilator.

Changes in blood glucose may occur. Large doses of intravenous racemic albuterol have been reported to aggravate preexisting diabetes mellitus and ketoacidosis.

5.8 Hypokalemia

As with other beta-adrenergic agonist medications, Levalbuterol Inhalation Solution, USP may produce significant hypokalemia in some patients, possibly through intracellular shunting, which has the potential to produce adverse cardiovascular effects. The decrease is usually transient, not requiring supplementation.

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of the drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adults and Adolescents 12 Years of Age and Older

Adverse reaction information concerning Levalbuterol Inhalation Solution, USP in adults and adolescents is derived from one 4-week, multicenter, randomized, double-blind, active-, and placebo-controlled trial in 362 patients with asthma 12 years of age and older. Adverse reactions reported in ≥ 2% of patients receiving Levalbuterol Inhalation Solution, USP or racemic albuterol and more frequently than in patients receiving placebo are listed in Table 1.

a One treatment group, racemic albuterol 1.25 mg, with 68 subjects is omitted.

The incidence of certain systemic beta-adrenergic adverse reactions (e.g., tremor, nervousness) was slightly less in the Levalbuterol Inhalation Solution, USP 0.63 mg group compared with the other active treatment groups. The clinical significance of these small differences is unknown.

Changes in heart rate 15 minutes after drug administration and in plasma glucose and potassium 1 hour after drug administration on day 1 and day 29 were clinically comparable in the Levalbuterol Inhalation Solution, USP 1.25 mg and racemic albuterol 2.5 mg groups (see Table 2). Changes in heart rate and plasma glucose were slightly less in the Levalbuterol Inhalation Solution, USP 0.63 mg group compared with the other active treatment groups (see Table 2). The clinical significance of these small differences is unknown. After 4 weeks, effects on heart rate, plasma glucose, and plasma potassium were generally diminished compared with day 1 in all active treatment groups.

No other clinically relevant laboratory abnormalities related to administration of Levalbuterol Inhalation Solution, USP were observed in this study.

In the clinical trials, a slightly greater number of serious adverse events, discontinuations due to adverse events, and clinically significant ECG changes were reported in patients who received Levalbuterol Inhalation Solution, USP 1.25 mg compared with the other active treatment groups.

The following adverse reactions, considered potentially related to Levalbuterol Inhalation Solution, USP, occurred in less than 2% of the 292 subjects who received Levalbuterol Inhalation Solution, USP and more frequently than in patients who received placebo in any clinical trial:

 The following reactions, considered potentially related to Levalbuterol Inhalation Solution, USP, occurred in less than 2% of the treated subjects but at a frequency less than in patients who received placebo: asthma exacerbation, cough increased, wheezing, sweating, and vomiting.

Pediatric Patients 6 to 11 Years of Age

Adverse reaction information concerning Levalbuterol Inhalation Solution, USP in pediatric patients is derived from one 3-week, multicenter, randomized, double-blind, active-, and placebo-controlled trial in 316 pediatric patients 6 to 11 years of age. Adverse reactions reported in ≥ 2% of patients in any treatment group and more frequently than in patients receiving placebo are listed in Table 3.

 Note: Subjects may have more than one adverse event per body system and preferred term.

Changes in heart rate, plasma glucose, and serum potassium are shown in Table 4. The clinical significance of these small differences is unknown.

6.2 Post-marketing Experience

In addition to the adverse reactions reported in clinical trials, the following adverse reactions have been observed in postapproval use of Levalbuterol Inhalation Solution, USP. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These events have been chosen for inclusion due to their seriousness, their frequency of reporting, or their likely beta-mediated mechanism: angioedema, anaphylaxis, arrhythmias (including atrial fibrillation, supraventricular tachycardia, extrasystoles), asthma, chest pain, cough increased, dysphonia, dyspnea, gastroesophageal reflux disease (GERD), metabolic acidosis, nausea, nervousness, rash, tachycardia, tremor, urticaria.

In addition, Levalbuterol Inhalation Solution, USP, like other sympathomimetic agents, can cause adverse reactions such as hypertension, angina, vertigo, central nervous system stimulation, sleeplessness, headache, and drying or irritation of the oropharynx.

7.1 Short-Acting Bronchodilators

Avoid concomitant use of other short-acting sympathomimetic bronchodilators or epinephrine in patients being treated with Levalbuterol Inhalation Solution, USP. If additional adrenergic drugs are to be administered by any route, they should be used with caution to avoid deleterious cardiovascular effects.

7.2 Beta-blockers

Beta-adrenergic receptor blocking agents not only block the pulmonary effect of beta-adrenergic agonists such as Levalbuterol Inhalation Solution, USP, but may produce severe bronchospasm in asthmatic patients. Therefore, patients with asthma should not normally be treated with beta-blockers. However, under certain circumstances, e.g., prophylaxis after myocardial infarction, there may be no acceptable alternatives to the use of beta-adrenergic blocking agents in patients with asthma. In this setting, cardioselective beta-blockers should be considered, although they should be administered with caution.

7.3 Diuretics

The ECG changes or hypokalemia that may result from the administration of non-potassium-sparing diuretics (such as loop and thiazide diuretics) can be acutely worsened by beta-agonists, especially when the recommended dose of the beta-agonist is exceeded. Although the clinical significance of these effects is not known, caution is advised in the coadministration of beta-agonists with non-potassium-sparing diuretics. Consider monitoring potassium levels.

7.4 Digoxin

Mean decreases of 16% and 22% in serum digoxin levels were demonstrated after single-dose intravenous and oral administration of racemic albuterol, respectively, to normal volunteers who had received digoxin for 10 days. The clinical significance of these findings for patients with obstructive airway disease who are receiving Levalbuterol Inhalation Solution, USP and digoxin on a chronic basis is unclear. Nevertheless, it would be prudent to carefully evaluate the serum digoxin levels in patients who are currently receiving digoxin and Levalbuterol Inhalation Solution, USP.

7.5 Monoamine Oxidase Inhibitors or Tricyclic Antidepressants

Levalbuterol Inhalation Solution, USP should be administered with extreme caution to patients being treated with monoamine oxidase inhibitors or tricyclic antidepressants, or within 2 weeks of discontinuation of such agents, because the action of levalbuterol on the vascular system may be potentiated. Consider alternative therapy in patients taking MAO inhibitors or tricyclic antidepressants.

8.1 Pregnancy

Risk Summary

There are no adequate and well-controlled studies of Levalbuterol Inhalation Solution, USP in pregnant women. There are clinical considerations with the use of Levalbuterol Inhalation Solution, USP in pregnant women [see Clinical Considerations].

Following oral administration of levalbuterol HCl to pregnant rabbits, there was no evidence of teratogenicity at doses up to 25 mg/kg/day [approximately 108 times the maximum recommended human daily inhalation dose (MRHDID) of levalbuterol HCl for adults on a mg/m2 basis]; however, racemic albuterol sulfate was teratogenic in mice (cleft palate) and rabbits (cramioschisis) at doses slightly higher than the human therapeutic range (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated population(s) are unknown. In the U.S. general population, the estimated risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20% respectively.

Clinical Considerations

Disease-Associated Maternal and/or Embryo/Fetal Risk

In women with poorly or moderately controlled asthma, there is an increased risk of preeclampsia in the mother and prematurity, low birth weight, and small for gestational age in the neonate. Pregnant women should be closely monitored and medication adjusted as necessary to maintain optimal control.

Labor or Delivery

Because of the potential for beta-adrenergic agonists to interfere with uterine contractility, the use of Levalbuterol Inhalation Solution, USP for the treatment of bronchospasm during labor should be restricted to those patients for whom the benefits clearly outweigh the risk.

Levalbuterol Inhalation Solution, USP has not been approved for the management of preterm labor. The benefit-risk ratio when Levalbuterol Inhalation Solution, USP is administered for tocolysis has not been established. Serious adverse reactions, including maternal pulmonary edema, have been reported during or following treatment of premature labor with beta2-agonists, including racemic albuterol.

Data

Animal Data

The oral administration of levalbuterol HCl to pregnant New Zealand White rabbits during the period of organogenesis found no evidence of teratogenicity at doses up to 25 mg/kg/day (approximately 108 times the MRHDID of levalbuterol HCl for adults on a mg/m2 basis). In a rat developmental study, racemic albuterol sulfate administered by inhalation did not produce any teratogenic effects at exposures approximately 63 times the MRHDID (on a mg/m2 basis at a maternal dose of 10.5 mg/kg).

However, other developmental studies with the racemic albuterol sulfate, did result in teratogenic effects in mice and rabbits at doses slightly higher than the human therapeutic range. In a rabbit developmental study, orally administered albuterol sulfate induced cranioschisis in 7 of 19 fetuses (37%) at approximately 215 times the MRHDID for adults (on a mg/m2 basis at a maternal dose of 50 mg/kg). In a mouse developmental study, subcutaneously administered albuterol sulfate produced cleft palate formation in 5 of 111 (4.5%) fetuses at an exposure approximately 0.3 times the MRHDID for adults (on a mg/m2 basis at a maternal dose of 0.25 mg/kg/day) and in 10 of 108 (9.3%) fetuses at approximately 3 times the MRHDID (on a mg/m2 basis at a maternal dose of 2.5 mg/kg/day). Similar effects were not observed at approximately 0.03 times the MRHDID for adults on a mg/m2 basis at a maternal dose of 0.025 mg/kg/day (i.e., less than the therapeutic dose). Cleft palate also occurred in 22 of 72 (30.5%) fetuses from females treated subcutaneously with isoproterenol (positive control).

8.2 Lactation

Risk Summary

There are no available data on the presence of levalbuterol in human milk, the effects on the breastfed child, or the effects on milk production.

The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for Levalbuterol Inhalation Solution, USP and any potential adverse effects on the breastfed child from Levalbuterol Inhalation Solution, USP or from the underlying maternal condition.

8.4 Pediatric Use

Pediatric Patients 6 Years of Age and Older

The safety and efficacy of Levalbuterol Inhalation Solution, USP have been established in pediatric patients 6 years of age and older in an adequate and well-controlled clinical trial [see Adverse Reactions (6) and Clinical Studies (14)].

Pediatric Patients less than 6 Years of Age

Levalbuterol Inhalation Solution, USP is not indicated for pediatric patients less than 6 years of age.

Clinical trials with Levalbuterol Inhalation Solution, USP in this age group failed to meet the primary efficacy endpoint and demonstrated an increased number of asthma-related adverse reactions following chronic Levalbuterol Inhalation Solution, USP treatment.

Levalbuterol Inhalation Solution, USP was studied in 379 pediatric patients less than 6 years of age with asthma or reactive airway disease - (291 patients 2 to 5 years of age, and 88 patients from birth to less than 2 years of age). Efficacy and safety data for Levalbuterol Inhalation Solution, USP in this age group are primarily available from one 3-week, multicenter, randomized, double-blind, active and placebo-controlled study (Study 1) in 211 pediatric patients between the ages of 2 and 5 years, of whom 119 received Levalbuterol Inhalation Solution, USP. Over the 3 week treatment period, there were no significant treatment differences in the Pediatric Asthma Questionnaire (PAQ) total score between groups receiving Levalbuterol Inhalation Solution, USP 0.31 mg, Levalbuterol Inhalation Solution, USP 0.63 mg, racemic albuterol, and placebo. Additional safety data following chronic dosing is available from a 4-week, multicenter, randomized, modified-blind, placebo-controlled study (Study 2) of 196 patients between the ages of birth and 3 years, of whom 63 received open-label Levalbuterol Inhalation Solution, USP. In these two studies, treatment-emergent asthma exacerbations or asthma-related adverse reactions and treatment discontinuations due to asthma occurred at a higher frequency in Levalbuterol Inhalation-treated subjects compared to control (Table 5). Other adverse reactions were consistent with those observed in the clinical trial population of patients 6 years of age and older [see Adverse Reactions (6.1)].

 * Asthma exacerbation defined as worsening of asthma symptoms or pulmonary function that required any of the following: emergency department visit, hospitalization, therapeutic intervention with oral or parenteral steroids, unscheduled clinic visit to treat acute asthma symptoms.
** Includes the following Preferred Terms (whether considered by the investigator to be related or unrelated to drug): asthma, cough, hypoxia, status asthmaticus, tachypnea.

8.5 Geriatric Use

Clinical studies of Levalbuterol Inhalation Solution, USP did not include sufficient numbers of subjects aged 65 years and older to determine whether they respond differently from younger subjects. Only 5 patients 65 years of age and older were treated with Levalbuterol Inhalation Solution, USP in a 4-week clinical study [see Clinical Pharmacology (12) and Clinical Studies (14)] (n = 2 for 0.63 mg and n = 3 for 1.25 mg). In these patients, bronchodilation was observed after the first dose on day 1 and after 4 weeks of treatment. In general, patients 65 years of age and older should be started at a dose of 0.63 mg of Levalbuterol Inhalation Solution, USP. If clinically warranted due to insufficient bronchodilator response, the dose of Levalbuterol Inhalation Solution, USP may be increased in elderly patients as tolerated, in conjunction with frequent clinical and laboratory monitoring, to the maximum recommended daily dose [see Dosage and Administration (2)].

8.6 Renal Impairment

Albuterol is known to be substantially excreted by the kidney, and the risk of toxic reactions 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.

12.1 Mechanism of Action

Activation of beta2-adrenergic receptors on airway smooth muscle leads to the activation of adenylate cyclase and to an increase in the intracellular concentration of cyclic-3′, 5′-adenosine monophosphate (cyclic AMP). The increase in cyclic AMP is associated with the activation of protein kinase A, which in turn inhibits the phosphorylation of myosin and lowers intracellular ionic calcium concentrations, resulting in muscle relaxation. Levalbuterol relaxes the smooth muscles of all airways, from the trachea to the terminal bronchioles. Increased cyclic AMP concentrations are also associated with the inhibition of release of mediators from mast cells in the airway. Levalbuterol acts as a functional antagonist to relax the airway irrespective of the spasmogen involved, thus protecting against all bronchoconstrictor challenges. While it is recognized that beta2-adrenergic receptors are the predominant receptors on bronchial smooth muscle, data indicate that there are beta-receptors in the human heart, 10% to 50% of which are beta2-adrenergic receptors. The precise function of these receptors has not been established [see Warnings and Precautions (5.4)]. However, all beta-adrenergic agonist drugs can produce a significant cardiovascular effect in some patients, as measured by pulse rate, blood pressure, symptoms, and/or electrocardiographic changes.

12.2 Pharmacodynamics

Adults and Adolescents ≥ 12 Years Old

 In a randomized, double-blind, placebo-controlled, cross-over study, 20 adults with mild-to-moderate asthma received single doses of Levalbuterol Inhalation Solution, USP (0.31 mg, 0.63 mg, and 1.25 mg) and racemic albuterol sulfate inhalation solution (2.5 mg). All doses of active treatment produced a significantly greater degree of bronchodilation (as measured by percent change from pre-dose mean FEV1) than placebo, and there were no significant differences between any of the active treatment arms. The bronchodilator responses to 1.25 mg of Levalbuterol Inhalation Solution, USP and 2.5 mg of racemic albuterol sulfate inhalation solution were clinically comparable over the 6-hour evaluation period, except for a slightly longer duration of action (> 15% increase in FEV1 from baseline) after administration of 1.25 mg of Levalbuterol Inhalation Solution, USP. Systemic beta-adrenergic adverse effects were observed with all active doses and were generally dose-related for (R)-albuterol. Levalbuterol Inhalation Solution, USP at a dose of 1.25 mg produced a slightly higher rate of systemic beta-adrenergic adverse effects than the 2.5 mg dose of racemic albuterol sulfate inhalation solution.

In a randomized, double-blind, placebo-controlled, cross-over study, 12 adults with mild-to-moderate asthma were challenged with inhaled methacholine chloride 20 and 180 minutes following administration of a single dose of 2.5 mg of racemic albuterol sulfate, 1.25 mg of Levalbuterol Inhalation Solution, USP, 1.25 mg of (S)-albuterol, or placebo using a Pari LC Jet™ nebulizer. Racemic albuterol sulfate, Levalbuterol Inhalation Solution, USP, and (S)-albuterol had a protective effect against methacholine-induced bronchoconstriction 20 minutes after administration, although the effect of (S)-albuterol was minimal. At 180 minutes after administration, the bronchoprotective effect of 1.25 mg of Levalbuterol Inhalation Solution, USP was comparable to that of 2.5 mg of racemic albuterol sulfate. At 180 minutes after administration, 1.25 mg of (S)-albuterol had no bronchoprotective effect.

In a clinical study in adults with mild-to-moderate asthma, comparable efficacy (as measured by change from baseline FEV1) and safety (as measured by heart rate, blood pressure, ECG, serum potassium, and tremor) were demonstrated after a cumulative dose of 5 mg of Levalbuterol Inhalation Solution, USP (four consecutive doses of 1.25 mg administered every 30 minutes) and 10 mg of racemic albuterol sulfate inhalation solution (four consecutive doses of 2.5 mg administered every 30 minutes).

12.3 Pharmacokinetics

Adults and Adolescents ≥ 12 Years Old

The inhalation pharmacokinetics of Levalbuterol Inhalation Solution, USP were investigated in a randomized cross-over study in 30 healthy adults following administration of a single dose of 1.25 mg and a cumulative dose of 5 mg of Levalbuterol Inhalation Solution, USP and a single dose of 2.5 mg and a cumulative dose of 10 mg of racemic albuterol sulfate inhalation solution by nebulization using a PARI LC Jet™ nebulizer with a Dura-Neb® 2000 compressor.

Following administration of a single 1.25 mg dose of Levalbuterol Inhalation Solution, USP, exposure to (R)-albuterol (AUC of 3.3 ng•hr/mL) was approximately 2-fold higher than following administration of a single 2.5 mg dose of racemic albuterol inhalation solution (AUC of 1.7 ng•hr/mL) (see Table 6). Following administration of a cumulative 5 mg dose of Levalbuterol Inhalation Solution, USP (1.25 mg given every 30 minutes for a total of four doses) or a cumulative 10 mg dose of racemic albuterol inhalation solution (2.5 mg given every 30 minutes for a total of four doses), Cmax and AUC of (R)-albuterol were comparable (see Table 6).

γMedian (Min, Max) reported for Tmax.
*A negative Tmax  indicates Cmax occurred between first and last nebulizations.
**Values reflect only (R)-albuterol and do not include (S)-albuterol.

Children 6-11 Years Old

The pharmacokinetic parameters of (R)-and (S)-albuterol in children with asthma were obtained using population pharmacokinetic analysis. These data are presented in Table 7. For comparison, adult data obtained by conventional pharmacokinetic analysis from a different study also are presented in Table 7.

In children, AUC and Cmax of (R)-albuterol following administration of 0.63 mg Levalbuterol Inhalation Solution, USP were comparable to those following administration of 1.25 mg racemic albuterol sulfate inhalation solution.

When the same dose of 0.63 mg of Levalbuterol Inhalation Solution, USP was given to children and adults, the predicted Cmax of (R)-albuterol in children was similar to that in adults (0.52 vs. 0.56 ng/mL), while predicted AUC in children (2.55 ng•hr/mL) was about 1.5-fold higher than that in adults (1.65 ng•hr/mL). These data support lower doses for children 6-11 years old compared with the adult doses [see Dosage and Administration (2)].

a The values are predicted by assuming linear pharmacokinetics
b The data obtained from Table 6
c Area under the plasma concentration curve from time 0 to infinity
d Maximum plasma concentration

Metabolism and Elimination

Information available in the published literature suggests that the primary enzyme responsible for the metabolism of albuterol enantiomers in humans is SULT1A3 (sulfotransferase). When racemic albuterol was administered either intravenously or via inhalation after oral charcoal administration, there was a 3- to 4-fold difference in the area under the concentration-time curves between the (R)- and (S)-albuterol enantiomers, with (S)-albuterol concentrations being consistently higher. However, without charcoal pretreatment, after either oral or inhalation administration the differences were 8- to 24-fold, suggesting that (R)-albuterol is preferentially metabolized in the gastrointestinal tract, presumably by SULT1A3.

The primary route of elimination of albuterol enantiomers is through renal excretion (80% to 100%) of either the parent compound or the primary metabolite. Less than 20% of the drug is detected in the feces. Following intravenous administration of racemic albuterol, between 25% and 46% of the (R)-albuterol fraction of the dose was excreted as unchanged (R)-albuterol in the urine.

Special Populations

Hepatic Impairment

 The effect of hepatic impairment on the pharmacokinetics of Levalbuterol Inhalation Solution, USP has not been evaluated.

Renal Impairment

The effect of renal impairment on the pharmacokinetics of racemic albuterol was evaluated in 5 subjects with creatinine clearance of 7 to 53 mL/min, and the results were compared with those from healthy volunteers. Renal disease had no effect on the half-life, but there was a 67% decline in racemic albuterol clearance. Caution should be used when administering high doses of Levalbuterol Inhalation Solution, USP to patients with renal impairment [see Use in Specific Populations (8.6)].

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Although there have been no carcinogenesis studies with levalbuterol HCl, racemic albuterol sulfate has been evaluated for its carcinogenic potential.

In a 2-year study in Sprague-Dawley rats, dietary administration of racemic albuterol sulfate resulted in a significant dose-related increase in the incidence of benign leiomyomas of the mesovarium at doses of 2 mg/kg/day and greater (approximately 4 times the MRHDID of levalbuterol HCl for adults and approximately 5 times the MRHDID of levalbuterol HCl for children on a mg/m2 basis). In an 18-month study in CD-1 mice and a 22-month study in the golden hamster, dietary administration of racemic albuterol sulfate showed no evidence of tumorigenicity. Dietary doses in CD-1 mice were up to 500 mg/kg/day (approximately 540 times the MRHDID of levalbuterol HCl for adults and approximately 630 times the MRHDID of levalbuterol HCl for children on a mg/m2 basis) and doses in the golden hamster study were up to 50 mg/kg/day (approximately 90 times the MRHDID of levalbuterol HCl for adults on a mg/m2 basis and approximately 105 times the MRHDID of levalbuterol HCl for children on a mg/m2 basis).

Levalbuterol HCl was not mutagenic in the Ames test or the CHO/HPRT Mammalian Forward Gene Mutation Assay. Levalbuterol HCl was not clastogenic in the in vivo micronucleus test in mouse bone marrow. Racemic albuterol sulfate was not clastogenic in an in vitro chromosomal aberration assay in CHO cell cultures.

No fertility studies have been conducted with levalbuterol hydrochloride. Reproduction studies in rats using racemic albuterol sulfate demonstrated no evidence of impaired fertility at oral doses up to 50 mg/kg/day (approximately 108 times the maximum recommended daily inhalation dose of levalbuterol HCl for adults on a mg/m2 basis).