Levalbuterol

INDICATIONS AND USAGE Levalbuterol inhalation solution (concentrate) is indicated for the treatment or prevention of bronchospasm in adults, adolescents, and children 6 years of age and older with reversible obstructive airway disease. Levalbuterol inhalation solution (concentrate) is a beta 2 -adrenergic agonist indicated for: • Treatment or prevention of bronchospasm in adults, adolescents, and children 6 years of age and older with reversible obstructive airway disease. ( 1 )

DOSAGE AND ADMINISTRATION Levalbuterol inhalation solution (concentrate) is for oral inhalation only. Dilute with sterile normal saline before administration. Administer by nebulization using with a standard jet nebulizer (with a face mask or mouthpiece) connected to an air compressor. Do not exceed recommended dose. For dosages less than 1.25 mg, the non-concentrate (i.e., levalbuterol inhalation solution, 3 mL) formulation must be used. Children 6 to 11 Years Old: The recommended dosage of levalbuterol inhalation solution for patients 6 to 11 years old is 0.31 mg administered three times a day, by nebulization. Routine dosing should not exceed 0.63 mg three times a day. Adults and Adolescents ≥ 12 Years Old: The recommended starting dosage of levalbuterol inhalation solution for patients 12 years of age and older is 0.63 mg administered three times a day, every 6 to 8 hours, by nebulization. Patients 12 years of age and older with more severe asthma or patients who do not respond adequately to a dose of 0.63 mg of levalbuterol inhalation solution may benefit from a dosage of 1.25 mg three times a day. Patients receiving the highest dose of levalbuterol inhalation solution should be monitored closely for adverse systemic effects, and the risks of such effects should be balanced against the potential for improved efficacy. The use of levalbuterol inhalation solution can be continued as medically indicated to help control recurring bouts of bronchospasm. During this time, most patients gain optimal benefit from regular use of the inhalation solution. If a previously effective dosage regimen fails to provide the usual response this may be a marker of destabilization of asthma and requires reevaluation of the patient and the treatment regimen, giving special consideration to the possible need for anti-inflammatory treatment, e.g., corticosteroids. The drug compatibility (physical and chemical), efficacy, and safety of levalbuterol inhalation solution when mixed with other drugs in a nebulizer have not been established. The safety and efficacy of levalbuterol inhalation solution have been established in clinical trials when administered using the PARI LC Jet™ and PARI LC Plus™ nebulizers, and the PARI Master ® Dura-Neb ® 2000 and Dura-Neb ® 3000 compressors. The safety and efficacy of levalbuterol inhalation solution when administered using other nebulizer systems have not been established. • FOR ORAL INHALATION ONLY ( 2 ) • Dilute levalbuterol inhalation solution (concentrate) with sterile normal saline before administration by nebulization. • Children 6 to 11 Years Old: 0.31 mg administered three times a day, by nebulization. Routine dosing should not exceed 0.63 mg three times a day. ( 2 ) • Adults and Adolescents ≥ 12 Years Old: 0.63 mg administered three times a day, every 6 to 8 hours, by nebulization. The maximum recommended dose is 1.25 mg three times a day. ( 2 ) • For use with a standard jet nebulizer (with a face mask or mouthpiece) connected to an air compressor. ( 2 )

WARNINGS AND PRECAUTIONS • Life-threatening paradoxical bronchospasm may occur. Discontinue Levalbuterol Inhalation Solution, USP immediately and treat with alternative therapy. ( 5.1 ) • Need for more doses of Levalbuterol Inhalation Solution, USP than usual may be a sign of deterioration of asthma and requires reevaluation of treatment. ( 5.2 ) • Levalbuterol Inhalation Solution, USP is not a substitute for corticosteroids. ( 5.3 ) • Cardiovascular effects may occur. Consider discontinuation of Levalbuterol Inhalation Solution, USP if these effects occur. Use with caution in patients with underlying cardiovascular disorders. ( 5.4 ) • Excessive use may be fatal. Do not exceed recommended dose. ( 5.5 ) • Immediate hypersensitivity reactions may occur. Discontinue Levalbuterol Inhalation Solution, USP immediately. ( 5.6 ) • Hypokalemia and changes in blood glucose may occur. ( 5.7 , 5.8 ) 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.

CONTRAINDICATIONS Levalbuterol tartrate HFA inhalation aerosol is contraindicated in patients with a history of hypersensitivity to levalbuterol, racemic albuterol, or any other component of Levalbuterol tartrate HFA inhalation aerosol. Reactions have included urticaria, angioedema, rash, bronchospasm, anaphylaxis, and oropharyngeal edema. Hypersensitivity to levalbuterol, racemic albuterol or any other component of Levalbuterol tartrate HFA inhalation aerosol. ( 4 )

DRUG INTERACTIONS Other short-acting sympathomimetic aerosol bronchodilators or epinephrine should not be used concomitantly with Levalbuterol tartrate HFA inhalation aerosol. If additional adrenergic drugs are to be administered by any route, they should be used with caution to avoid deleterious cardiovascular effects. Other short-acting sympathomimetic aerosol bronchodilators and adrenergic drugs : May potentiate effect. ( 7 ) Beta-blockers : May block bronchodilatory effects of beta-agonists and produce severe bronchospasm. Patients with asthma should not normally be treated with beta-blockers. ( 7.1 ) Diuretics : May worsen electrocardiographic changes or hypokalemia associated with diuretics may worsen. Consider monitoring potassium levels. ( 7.2 ) Digoxin : May decrease serum digoxin levels. Consider monitoring digoxin levels. ( 7.3 ) Monoamine oxidase inhibitors (MAOs) or tricyclic antidepressants : May potentiate effect of albuterol on the cardiovascular system. Consider alternative therapy in patients taking MAO inhibitors or tricyclic antidepressants. ( 7.4 ) 7.1 Beta-blockers Beta-blockers: Beta-adrenergic receptor blocking agents not only block the pulmonary effect of beta-adrenergic agonists, such as Levalbuterol tartrate HFA inhalation aerosol, 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., as 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. 7.2 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. 7.3 Digoxin Mean decreases of 16% to 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 tartrate HFA inhalation aerosol 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 tartrate HFA inhalation aerosol. 7.4 Monoamine Oxidase Inhibitors or Tricyclic Antidepressants Levalbuterol tartrate HFA inhalation aerosol 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 albuterol on the vascular system may be potentiated. Consider alternative therapy in patients taking MAO inhibitors or tricyclic antidepressants.

ADVERSE REACTIONS The following serious adverse reactions are described below and elsewhere in the labeling: • Paradoxical bronchospasm [see Warnings and Precautions (5.1) ] • Cardiovascular effects [see Warnings and Precautions (5.4) ] • Immediate hypersensitivity reactions [see Warnings and Precautions (5.6) ] • Hypokalemia [see Warnings and Precautions (5.8) ] Most common adverse reactions are: palpitations, chest pain, tachycardia, headache, dizziness, tremor and nervousness. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 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 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 or racemic albuterol and more frequently than in patients receiving placebo are listed in Table 1. Table 1: Adverse Reactions Reported in a 4-Week, Controlled Clinical Trial in Adults and Adolescents ≥ 12 Years Old Body System Preferred Term Percent of Patients One treatment group, racemic albuterol 1.25 mg, with 68 subjects is omitted. Placebo (n = 75) Levalbuterol Inhalation Solution 1.25 mg (n = 73) Levalbuterol Inhalation Solution 0.63 mg (n = 72) Racemic Albuterol 2.5 mg (n = 74) Body as a Whole Allergic reaction 1.3 0 0 2.7 Flu syndrome 0 1.4 4.2 2.7 Accidental injury 0 2.7 0 0 Pain 1.3 1.4 2.8 2.7 Back pain 0 0 0 2.7 Cardiovascular System Tachycardia 0 2.7 2.8 2.7 Migraine 0 2.7 0 0 Digestive System Dyspepsia 1.3 2.7 1.4 1.4 Musculoskeletal System Leg cramps 1.3 2.7 0 1.4 Central Nervous System Dizziness 1.3 2.7 1.4 0 Hypertonia 0 0 0 2.7 Nervousness 0 9.6 2.8 8.1 Tremor 0 6.8 0 2.7 Anxiety 0 2.7 0 0 Respiratory System Cough increased 2.7 4.1 1.4 2.7 Infection viral 9.3 12.3 6.9 12.2 Rhinitis 2.7 2.7 11.1 6.8 Sinusitis 2.7 1.4 4.2 2.7 Turbinate edema 0 1.4 2.8 0 The incidence of certain systemic beta-adrenergic adverse reactions (e.g., tremor, nervousness) was slightly less in the levalbuterol inhalation solution 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 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 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. Table 2: Mean Changes from Baseline Heart Rate at 15 Minutes and Glucose and Potassium at 1 Hour after First Dose (Day 1) in Adults and Adolescents ≥ 12 Years Old Treatment Mean Changes (Day 1) Heart Rate (bpm) Glucose (mg/dL) Potassium (mEq/L) Levalbuterol Inhalation Solution 0.63 mg, n = 72 2.4 4.6 -0.2 Levalbuterol Inhalation Solution 1.25 mg, n = 73 6.9 10.3 -0.3 Racemic Albuterol 2.5 mg, n = 74 5.7 8.2 -0.3 Placebo, n = 75 -2.8 -0.2 -0.2 No other clinically relevant laboratory abnormalities related to administration of levalbuterol inhalation solution 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 1.25 mg compared with the other active treatment groups. The following adverse reactions, considered potentially related to levalbuterol inhalation solution, occurred in less than 2% of the 292 subjects who received levalbuterol inhalation solution and more frequently than in patients who received placebo in any clinical trial: Body as a Whole: chills, pain, chest pain Cardiovascular System: ECG abnormal, ECG change, hypertension, hypotension, syncope Digestive System: diarrhea, dry mouth, dry throat, dyspepsia, gastroenteritis, nausea Hemic and Lymphatic System: lymphadenopathy Musculoskeletal System: leg cramps, myalgia Nervous System: anxiety, hyperesthesia of the hand, insomnia, paresthesia, tremor Special Senses: eye itch The following reactions, considered potentially related to levalbuterol inhalation solution, 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 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. Table 3: Most Frequently Reported Adverse Reactions (≥ 2% in Any Treatment Group) and Those Reported More Frequently Than in Placebo during the Double-Blind Period (ITT Population, 6 to 11 Years Old) Body System Preferred Term Percent of Patients Placebo (n = 59) Levalbuterol Inhalation Solution 0.31 mg (n = 66) Levalbuterol Inhalation Solution 0.63 mg (n = 67) Racemic Albuterol 1.25 mg (n = 64) Racemic Albuterol 2.5 mg (n = 60) Body as a Whole Abdominal pain 3.4 0 1.5 3.1 6.7 Accidental injury 3.4 6.1 4.5 3.1 5.0 Asthenia 0 3.0 3.0 1.6 1.7 Fever 5.1 9.1 3.0 1.6 6.7 Headache 8.5 7.6 11.9 9.4 3.3 Pain 3.4 3.0 1.5 4.7 6.7 Viral infection 5.1 7.6 9.0 4.7 8.3 Digestive System Diarrhea 0 1.5 6.0 1.6 0 Hemic and Lymphatic Lymphadenopathy 0 3.0 0 1.6 0 Musculoskeletal System Myalgia 0 0 1.5 1.6 3.3 Respiratory System Asthma 5.1 9.1 9.0 6.3 10.0 Pharyngitis 6.8 3.0 10.4 0 6.7 Rhinitis 1.7 6.1 10.4 3.1 5.0 Skin and Appendages Eczema 0 0 0 0 3.3 Rash 0 0 7.5 1.6 0 Urticaria 0 0 3.0 0 0 Special Senses Otitis media 1.7 0 0 0 3.3 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. Table 4: Mean Changes from Baseline Heart Rate at 30 Minutes and Glucose and Potassium at 1 Hour after First Dose (Day 1) and Last Dose (Day 21) in Children 6 to 11 Years Old Treatment Mean Changes (Day 1) Heart Rate (bpm) Glucose (mg/dL) Potassium (mEq/L) Levalbuterol Inhalation Solution 0.31 mg, n = 66 0.8 4.9 -0.31 Levalbuterol Inhalation Solution 0.63 mg, n = 67 6.7 5.2 -0.36 Racemic Albuterol 1.25 mg, n = 64 6.4 8.0 -0.27 Racemic Albuterol 2.5 mg, n = 60 10.9 10.8 -0.56 Placebo, n = 59 -1.8 0.6 -0.05 Treatment Mean Changes (Day 21) Heart Rate (bpm) Glucose (mg/dL) Potassium (mEq/L) Levalbuterol Inhalation Solution 0.31 mg, n = 60 0 2.6 -0.32 Levalbuterol Inhalation Solution 0.63 mg, n = 66 3.8 5.8 -0.34 Racemic Albuterol 1.25 mg, n = 62 5.8 1.7 -0.18 Racemic Albuterol 2.5 mg, n = 54 5.7 11.8 -0.26 Placebo, n = 55 -1.7 1.1 -0.04 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. Because these reactions are reported voluntarily f

Clinical Pharmacology 12.1 Mechanism of Action Activation of beta 2 -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 beta 2 -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 beta 2 -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 FEV 1 ) 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 FEV 1 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 FEV 1 ) 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), C max and AUC of (R)-albuterol were comparable (see Table 6). Table 6 - Mean (SD) Values for Pharmacokinetic Parameters in Healthy Adults Single Dose Cumulative Dose Levalbuterol Inhalation Solution, USP 1.25 mg Racemic albuterol sulfate 2.5 mg Levalbuterol Inhalation Solution, USP 5 mg Racemic albuterol sulfate 10 mg C max (ng/mL) (R)-albuterol 1.1 (0.45) 0.8 (0.41)** 4.5 (2.20) 4.2 (1.51)** T max (h) γ (R)-albuterol 0.2 (0.17, 0.37) 0.2 (0.17, 1.50) 0.2 (-0.18*, 1.25) 0.2 (-0.28*, 1.00) AUC (ng•h/mL) (R)-albuterol 3.3 (1.58) 1.7 (0.99)** 17.4 (8.56) 16.0 (7.12)** T½ (h) (R)-albuterol 3.3 (2.48) 1.5 (0.61) 4.0 (1.05) 4.1 (0.97) γ Median (Min, Max) reported for T max . *A negative T max indicates C max 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 C max 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 C max 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 ) ]. Table 7 - (R)-Albuterol Exposure in Adults and Pediatric Subjects (6-11 years) Children 6- 11 years Adults ≥ 12 years Treatment Levalbuterol Inhalation Solution, USP 0.31 mg Levalbuterol Inhalation Solution, USP 0.63 mg Racemic albuterol 1.25 mg Racemic albuterol 2.5 mg Levalbuterol Inhalation Solution, USP 0.63 mg Levalbuterol Inhalation Solution,USP 1.25 mg AUC0-∞ (ng•hr/mL) c 1.36 2.55 2.65 5.02 1.65 a 3.3 b C max (ng/mL) d 0.303 0.521 0.553 1.08 0.56 a 1.1 b 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, the