What is the recommended dose conversion from salbutamol (albuterol) to levosalbutamol (levalbuterol)?

Salbutamol to Levosalbutamol Dose Conversion

Levosalbutamol should be administered at half the milligram dose of racemic salbutamol to achieve equivalent bronchodilation. 1

Conversion Ratios by Formulation

Nebulized Solutions

For children:

• Salbutamol: 0.15 mg/kg (minimum 2.5 mg) converts to Levosalbutamol: 0.075 mg/kg (minimum 1.25 mg) 1, 2
• This 2:1 conversion ratio applies across all pediatric dosing scenarios 1

For adults:

• Salbutamol: 2.5-5 mg converts to Levosalbutamol: 1.25-2.5 mg 1, 3
• Standard adult salbutamol dose of 5 mg equals levosalbutamol 2.5 mg 3

Metered-Dose Inhalers (MDI)

The conversion ratio is also 2:1 for MDI formulations:

• Salbutamol MDI: 90 mcg/puff converts to Levosalbutamol MDI: 45 mcg/puff 1
• For acute exacerbations: 4-8 puffs of either formulation every 20 minutes for 3 doses, then every 1-4 hours as needed 1, 2

Pharmacologic Basis for Conversion

The 2:1 ratio exists because racemic salbutamol contains equal amounts of R-enantiomer (active levosalbutamol) and S-enantiomer (therapeutically inactive). 4, 5

• Beta2-agonist activity resides almost exclusively in the R-enantiomer 4
• Clinical studies demonstrate that 100 mcg levosalbutamol produces equivalent bronchodilation to 200 mcg racemic salbutamol 6
• The relative dose potency has been confirmed as approximately 2:1 across multiple formulations 1, 5

Acute Exacerbation Dosing Schedules

Initial treatment protocol (both formulations):

• Administer every 20 minutes for 3 doses 1, 2, 7
• Then adjust to every 1-4 hours based on severity and clinical response 1, 2

For severe exacerbations:

• Consider hourly or continuous nebulization 1, 7
• Add ipratropium bromide (0.25-0.5 mg for children, 500 mcg for adults) to enhance bronchodilation 1, 2, 3

Administration Technique Considerations

Proper dilution is essential for optimal drug delivery:

• Dilute nebulizer solutions to a minimum of 3-4 mL with normal saline 2, 3
• Use gas flow of 6-8 L/min for nebulization 1, 2
• Continue nebulization until approximately one minute after "spluttering" occurs (typically 5-10 minutes) 3

Clinical Equivalence and Safety

Levosalbutamol at half the dose demonstrates equivalent or slightly superior efficacy compared to racemic salbutamol: 1, 8

• One pediatric study showed levosalbutamol produced better improvement in respiratory rate (24.4 vs 27.6/min), heart rate (115.5 vs 124.5/min), and oxygen saturation (97.2% vs 95.0%) compared to racemic salbutamol 8
• Racemic salbutamol causes more tachycardia due to the S-enantiomer 8
• However, well-designed clinical studies have not found significant toxicity from S-salbutamol in racemic formulations 4

Common Pitfalls to Avoid

Do not use equal milligram doses of levosalbutamol and salbutamol - this would result in double the intended beta-agonist effect and increased adverse effects 1, 2

Always use minimum doses even when weight-based calculations suggest lower amounts:

• Children: minimum 1.25 mg levosalbutamol (vs 2.5 mg salbutamol) 1, 2
• Adults: minimum 1.25 mg levosalbutamol (vs 2.5 mg salbutamol) 1, 3

Monitor for adverse effects with both formulations:

• Tachycardia, tremor, and hypokalemia require monitoring, especially with frequent dosing 2, 7, 3
• Use caution in patients with cardiovascular disorders, hyperthyroidism, and diabetes 2