Xopenex (Levalbuterol)
levalbuterol tartrate (MDI) · levalbuterol HCl (nebulizer solution)
Indications for Levalbuterol
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Treatment or prevention of bronchospasm in reversible obstructive airway disease | ≥4 years (Xopenex HFA MDI); ≥6 years (Xopenex nebulizer solution) | PRN reliever / rescue | FDA Approved |
Levalbuterol is the purified (R)-enantiomer of racemic albuterol, which is the pharmacologically active isomer responsible for bronchodilation. The (S)-enantiomer present in racemic albuterol is inactive at the beta-2 receptor but is metabolized more slowly, potentially accumulating in lung tissue. Levalbuterol was developed with the rationale that removing the (S)-enantiomer might provide equivalent bronchodilation at lower doses with fewer systemic side effects. However, clinical data have not consistently demonstrated a clinically meaningful advantage over racemic albuterol at equivalent bronchodilating doses, and most guidelines treat them as therapeutically interchangeable for routine use.
Despite theoretical advantages, meta-analyses and systematic reviews have not established clear superiority of levalbuterol over racemic albuterol for acute asthma or routine bronchospasm at equipotent doses. The GINA and NAEPP guidelines do not preferentially recommend levalbuterol over racemic albuterol. Cost considerations often favor racemic albuterol, particularly for nebulized formulations. Levalbuterol may be considered in patients who report intolerable tremor or tachycardia with racemic albuterol, though evidence for this benefit is limited.
Dosing of Levalbuterol
MDI Dosing (Xopenex HFA)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Acute bronchospasm — adults and children ≥4 years | 2 puffs (90 mcg) PRN | 2 puffs q4–6h PRN | Not established; do not exceed recommended frequency | 1 puff (45 mcg) q4h may suffice in some patients Each actuation delivers 45 mcg levalbuterol base (= 59 mcg levalbuterol tartrate) (FDA PI) |
Nebulizer Dosing (Xopenex Inhalation Solution)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Bronchospasm — adults and adolescents ≥12 years | 0.63 mg nebulized TID | 0.63 mg q6–8h | 1.25 mg TID | Increase to 1.25 mg TID only with close monitoring for adverse effects Deliver via standard jet nebulizer over 5–15 min; do not mix with other drugs in nebulizer (FDA PI) |
| Bronchospasm — children 6–11 years | 0.31 mg nebulized TID | 0.31 mg q8h | 0.63 mg TID | Routine dosing should not exceed 0.63 mg TID Not indicated for children <6 years (nebulizer); clinical trials in <6 years failed primary efficacy endpoint (FDA PI) |
| Acute asthma exacerbation — ED (off-label dosing) | 1.25–2.5 mg nebulized q20min ×3 | 1.25–2.5 mg q1–4h PRN | Per clinical judgment | Equivalent to racemic albuterol 2.5–5 mg at ~half the dose for R-enantiomer content Most ED protocols use racemic albuterol; levalbuterol has no proven ED advantage |
Levalbuterol 0.63 mg delivers the same amount of active (R)-albuterol as racemic albuterol 1.25 mg (since racemic albuterol is a 50:50 mixture of R and S enantiomers). Similarly, levalbuterol 1.25 mg is equivalent in R-enantiomer content to racemic albuterol 2.5 mg. At these equivalent R-albuterol doses, the bronchodilatory efficacy is comparable. Any perceived clinical advantage of levalbuterol at the labeled doses largely reflects comparison with a higher total beta-agonist load from racemic albuterol.
Shake well before each use. Prime with 4 test sprays before first use or after >3 days of non-use. Clean the actuator weekly with warm water and air-dry thoroughly. Discard when dose indicator shows zero (200 actuations). Do not use with actuators from other products (FDA PI).
Pharmacology of Levalbuterol
Mechanism of Action
Levalbuterol is the isolated (R)-enantiomer of albuterol, which is the stereoisomer responsible for virtually all bronchodilatory activity. It activates beta-2 adrenergic receptors on airway smooth muscle, stimulating adenylate cyclase to increase intracellular cyclic AMP. This triggers protein kinase A activation, myosin dephosphorylation, and reduced intracellular calcium, leading to smooth muscle relaxation from the trachea to the terminal bronchioles. Levalbuterol also stabilizes mast cell membranes to inhibit mediator release and enhances mucociliary clearance. The (S)-enantiomer of albuterol, which is absent from levalbuterol preparations, has no bronchodilatory activity but undergoes slower metabolism and may accumulate in lung tissue, where it has been hypothesized to promote airway inflammation and hyperresponsiveness, though the clinical significance of this remains debated.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Inhaled: rapid pulmonary absorption; MDI Cmax ~199 pg/mL (90 mcg dose, adults); systemic exposure 13–16% less than equivalent racemic albuterol 180 mcg in adults, 30–32% less in children | Low systemic levels at standard inhaled doses minimize cardiovascular side effects; pulmonary Tmax within minutes |
| Distribution | Not extensively protein-bound; widely distributed; crosses the placenta | Low protein binding means displacement interactions are not a clinical concern |
| Metabolism | Primary enzyme SULT1A3 (sulfotransferase); metabolized to inactive 4′-O-sulfate; (R)-albuterol cleared faster than (S)-albuterol by 3–4 fold; minimal CYP involvement | Faster clearance of the active R-enantiomer means the inactive S-enantiomer from racemic albuterol accumulates preferentially; levalbuterol avoids this S-enantiomer load |
| Elimination | t½ 3.3 h (single nebulized 1.25 mg); 4.0 h (multiple nebulized doses); renally excreted as parent drug and sulfate metabolite | Short half-life supports q4–8h dosing; substantially excreted by kidneys — caution in renal impairment |
Side Effects of Levalbuterol
Adverse event data for Xopenex HFA are derived from two 8-week clinical trials in adults and adolescents (N=403 vs placebo N=166) and one 4-week trial in children aged 4–11 (N=76 vs placebo N=35). The side effect profile is generally comparable to racemic albuterol. The incidence of systemic beta-adrenergic effects (tremor, nervousness) was low and comparable across all treatment groups including placebo in the pediatric study (FDA PI).
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Vomiting (pediatric 4–11 years) | 11% vs 6% placebo | More common in pediatric population; usually self-limiting; consider relationship to swallowed drug fraction |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Asthma exacerbation | 9% (adults) vs 6% placebo | Likely reflects underlying disease rather than drug effect; if worsening, reassess controller therapy |
| Accidental injury (pediatric) | 9% (pediatric) vs 6% placebo | Not directly drug-related; reflects typical pediatric trial reporting |
| Pharyngitis | 8% (adults) vs 2% placebo; 7% (pediatric) vs 6% placebo | Local aerosol deposition effect; rinsing mouth after use may help |
| Rhinitis | 7% (adults) vs 3% placebo | Upper respiratory tract effect; differentiate from allergic rhinitis |
| Pain | 4% (adults) vs 4% placebo | Non-specific; not clearly drug-related given comparable placebo rate |
| Dizziness | 3% (adults) vs 2% placebo | Mild; likely beta-adrenergic mediated; advise caution with driving if affected |
| Bronchitis (pediatric) | 3% (pediatric) vs 0% placebo | May reflect intercurrent respiratory infection in pediatric population |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Paradoxical bronchospasm | Rare | During or immediately after inhalation; often with first use of new canister | Discontinue immediately; institute alternative bronchodilator; may be life-threatening |
| Anaphylaxis / angioedema | Rare (post-marketing) | During or shortly after administration | Discontinue immediately; treat with epinephrine; do not rechallenge; note cross-reactivity with racemic albuterol |
| Cardiac arrhythmias (AF, SVT, extrasystoles) | Rare (post-marketing) | Minutes to hours; dose-related | ECG monitoring; reduce dose or discontinue; caution in patients with cardiovascular disease or concurrent QT-prolonging drugs |
| Hypokalemia | Uncommon at standard doses | Within 1–2 hours of high-dose use | Transcellular shift mechanism; monitor K+ with high-dose use; exacerbated by diuretics and corticosteroids |
| Metabolic acidosis (lactic acidosis) | Rare (post-marketing) | Hours of high-dose therapy | Check ABG and lactate; compensatory tachypnea may mimic worsening asthma; reduce or stop beta-agonist |
| Cardiac arrest / death with excessive use | Very rare | Associated with chronic overuse | Do not exceed recommended dose; increasing SABA use signals need for controller escalation |
Drug Interactions with Levalbuterol
Levalbuterol shares the same drug interaction profile as racemic albuterol. Interactions are predominantly pharmacodynamic, involving other sympathomimetic agents, drugs that affect cardiac rhythm, and agents altering potassium balance. Levalbuterol is not a significant CYP substrate.
Monitoring for Levalbuterol
- SABA Use FrequencyEvery visit
RoutineIncreasing use of any SABA (including levalbuterol) is a marker of deteriorating asthma control. Reassess controller therapy, inhaler technique, and adherence if use exceeds 2 days/week or ≥3 canisters/year. - Heart Rate & Blood PressureDuring acute high-dose therapy
Trigger-basedCardiovascular effects are dose-related. Monitor continuously during frequent nebulized dosing in ED/ICU settings. Beta-agonists can produce ECG changes including QTc prolongation, T-wave flattening, and ST depression. - Serum PotassiumWith high-dose or continuous use
Trigger-basedIntracellular potassium shift may produce transient hypokalemia. Risk amplified by concurrent corticosteroids and diuretics. - Blood GlucoseIn diabetic patients; with high-dose use
Trigger-basedBeta-2 agonists stimulate hepatic gluconeogenesis. Usually clinically insignificant at standard doses but may be relevant in diabetic patients. - Respiratory ResponseDuring acute exacerbation
RoutineAssess FEV1 or PEF 15–30 min after each nebulizer treatment. Poor response should prompt escalation (ipratropium, systemic corticosteroids, magnesium sulfate). - Renal FunctionBaseline in elderly or renal impairment
Trigger-basedAlbuterol is substantially renally excreted. Risk of adverse effects may be greater in patients with impaired renal function (FDA PI).
Contraindications & Cautions for Levalbuterol
Absolute Contraindications
- Known hypersensitivity to levalbuterol, racemic albuterol, or any component of the formulation — reactions have included urticaria, angioedema, rash, bronchospasm, anaphylaxis, and oropharyngeal edema (FDA PI)
Relative Contraindications (Specialist Input Recommended)
- Cardiovascular disease: Patients with coronary insufficiency, cardiac arrhythmias, or hypertension should use levalbuterol with caution. ECG changes (QTc prolongation, T-wave flattening, ST depression) may occur.
- Concurrent non-selective beta-blocker use: May block bronchodilatory effect and provoke severe bronchospasm.
Use with Caution
- Convulsive disorders: Sympathomimetic stimulation may lower seizure threshold.
- Hyperthyroidism: Enhanced sympathomimetic sensitivity.
- Diabetes mellitus: May increase blood glucose.
- Pregnancy: No adequate controlled studies. Levalbuterol was not teratogenic in rabbits at up to 750 times MRHDID. Racemic albuterol caused cleft palate in mice and cranioschisis in rabbits at higher doses. Use only if benefit outweighs risk; poorly controlled asthma poses greater risk to mother and fetus.
- Lactation: Unknown whether excreted in human milk. Due to tumorigenicity of racemic albuterol in animal studies, weigh risks vs benefits for nursing mothers.
- Pediatric <4 years (MDI) / <6 years (nebulizer): Not indicated. Clinical trial in children <4 years failed to show efficacy and showed more asthma-related adverse events than placebo.
- Elderly: Use with caution, starting at the low end of the dosing range. Monitor renal function.
- Renal impairment: Albuterol is substantially excreted by kidneys; risk of toxic reactions may be greater.
Fatalities have been reported in association with excessive use of inhaled sympathomimetic drugs in patients with asthma. Cardiac arrest following severe acute asthmatic crisis and subsequent hypoxia is suspected. Patients should not exceed the recommended dose. Increasing SABA use signals deteriorating asthma requiring urgent reassessment and controller therapy escalation (FDA PI).
Patient Counselling for Levalbuterol
Purpose of Therapy
Levalbuterol is a quick-relief (“rescue”) bronchodilator that opens the airways rapidly during episodes of wheezing, shortness of breath, or chest tightness. It contains only the active form of albuterol, which may reduce some side effects such as shaking or rapid heartbeat in certain patients. Like all rescue inhalers, levalbuterol does not treat the underlying inflammation in asthma and should not be used as the sole long-term treatment.
How to Use
For the MDI: shake well, breathe out fully, seal lips around the mouthpiece, press the canister while breathing in slowly and deeply, and hold breath for up to 10 seconds. Wait at least 1 minute between puffs. A spacer may improve delivery. Prime with 4 sprays before first use or after >3 days of non-use. Discard when the dose counter shows zero.
Sources
- XOPENEX HFA (levalbuterol tartrate) Inhalation Aerosol. Full Prescribing Information. Sunovion Pharmaceuticals Inc. Revised 02/2017. FDA Label (PDF)Primary source for MDI dosing, adverse event tables (Tables 1–3), pharmacokinetic data, and contraindications.
- XOPENEX (levalbuterol HCl) Inhalation Solution. Full Prescribing Information. Sunovion Pharmaceuticals Inc. DailyMedSource for nebulizer solution dosing, PK data (half-life 3.3–4 h), duration of effect, and pediatric dosing for ages 6–11.
- XOPENEX (levalbuterol HCl) Inhalation Solution Concentrate. Full Prescribing Information. DailyMedSource for the 1.25 mg/0.5 mL concentrate formulation requiring dilution with sterile normal saline.
- Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention, 2024 Update. ginasthma.orgInternational asthma guideline; does not preferentially recommend levalbuterol over racemic albuterol for routine SABA use.
- National Asthma Education and Prevention Program (NAEPP). Expert Panel Report 4 (EPR-4), 2020. doi:10.1016/j.jaci.2020.10.003US guidelines treating levalbuterol and racemic albuterol as therapeutically interchangeable for stepwise asthma therapy.
- Hendeles L, Colice GL, Meyer RJ. Withdrawal of albuterol inhalers containing chlorofluorocarbon propellants. N Engl J Med. 2007;356(13):1344–1351. doi:10.1056/NEJMra050380Reviews the transition from CFC to HFA inhalers and positions levalbuterol in the context of available SABA formulations.
- Jat KR, Khairwa A. Levalbuterol versus albuterol for acute asthma: a systematic review and meta-analysis. Pulm Pharmacol Ther. 2013;26(2):239–248. doi:10.1016/j.pupt.2012.11.003Meta-analysis finding no significant clinical advantage of levalbuterol over racemic albuterol for acute asthma at equipotent doses.
- Carl JC, Myers TR, Kirchner HL, et al. Comparison of racemic albuterol and levalbuterol for treatment of acute asthma. J Pediatr. 2003;143(6):731–736. doi:10.1067/S0022-3476(03)00489-1Pediatric RCT comparing levalbuterol and racemic albuterol in the ED; showed reduced hospitalization with levalbuterol, but subsequent larger studies did not replicate this.
- Qureshi F, Zaritsky A, Welch C, et al. Clinical efficacy of racemic albuterol versus levalbuterol for the treatment of acute pediatric asthma. Ann Emerg Med. 2005;46(1):29–36. doi:10.1016/j.annemergmed.2005.02.006Large pediatric ED study finding no significant difference in hospitalization rates between levalbuterol and racemic albuterol.
- Nelson HS, Bensch G, Pleskow WW, et al. Improved bronchodilation with levalbuterol compared with racemic albuterol in patients with asthma. J Allergy Clin Immunol. 1998;102(6 Pt 1):943–952. doi:10.1016/S0091-6749(98)70333-7Early pivotal study supporting levalbuterol efficacy; demonstrated bronchodilation at half the racemic dose.
- Ameredes BT, Calhoun WJ. (R)-albuterol for asthma: pro (R vs S). Am J Respir Crit Care Med. 2006;174(9):965–969. doi:10.1164/rccm.2606003Review of the enantiomer debate, including the theoretical basis for removing the S-isomer and its clinical significance.
- Boulton DW, Fawcett JP. Enantioselective disposition of salbutamol in man following oral and intravenous administration. Br J Clin Pharmacol. 1996;41(1):35–40. doi:10.1111/j.1365-2125.1996.tb00154.xDemonstrates the 3–4 fold difference in clearance between R- and S-albuterol enantiomers in humans.