Salbutamol MDI Dose in Asthma Exacerbation
For adults and children ≥4 years with moderate-to-severe acute asthma exacerbation, administer 4–8 puffs (360–720 mcg) of salbutamol via metered-dose inhaler with spacer every 20 minutes for three doses during the first hour, then every 1–4 hours as needed based on clinical response. 1, 2, 3
Initial Treatment Protocol (First Hour)
Deliver 4–8 puffs every 20 minutes for three consecutive treatment sessions to achieve maximal bronchodilation when airways are most constricted. 1, 2 Each puff delivers 90 mcg of salbutamol base (108 mcg salbutamol sulfate from the actuator). 3
- Adults: 4–8 puffs (360–720 mcg) per treatment session 1, 2
- Children ≥4 years: 4–8 puffs per treatment session 1, 2
- Children <4 years: Use spacer with face mask; same dosing applies 1, 4
Administer all 4–8 puffs rapidly in succession (within 1–2 minutes) using proper spacer technique: actuate one puff at a time into the spacer, have the patient perform a slow deep inhalation immediately after each actuation, followed by a 10-second breath-hold. 2 The 20-minute interval refers to the time between complete treatment sessions, not between individual puffs. 2
Maintenance Phase (After First Hour)
Continue salbutamol 4–8 puffs every 1–4 hours as needed, with the specific interval determined by severity of ongoing symptoms and observed response. 1, 2, 3 Gradually decrease frequency as clinical improvement occurs. 2
Equivalence to Nebulizer Therapy
MDI with spacer is equally effective as nebulized therapy for mild-to-moderate exacerbations when proper technique is used and coaching is provided. 1, 2 However, nebulized therapy remains preferred for severe exacerbations because it provides more reliable drug delivery when airways are severely constricted and allows simultaneous oxygen administration. 2
- Nebulizer equivalent: 2.5–5 mg salbutamol every 20 minutes for three doses 5, 1
- MDI dose range: 4–8 puffs delivers 360–720 mcg, which is lower than nebulizer dosing but achieves comparable bronchodilation in mild-to-moderate cases 1, 2
Critical Adjunctive Therapy
Add ipratropium bromide 8 puffs (or 0.5 mg nebulized) to salbutamol every 20 minutes for three doses in all moderate-to-severe exacerbations. 1, 2 This combination significantly reduces hospitalization rates, particularly in patients with severe airflow obstruction. 1, 2
Administer systemic corticosteroids immediately without delaying while "trying bronchodilators first"—prednisolone 40–60 mg orally for adults or 1–2 mg/kg (maximum 60 mg) for children. 1, 2 Clinical benefits require 6–12 hours minimum to manifest. 1
Reassessment & Escalation
Measure peak expiratory flow (PEF) or FEV₁ before treatment and 15–30 minutes after the first bronchodilator dose to objectively assess severity and response. 1, 2 The 30-minute response is the most important predictor of outcome—not the initial severity. 6
Response-Based Management:
- Good response (PEF >75% predicted): Continue maintenance therapy every 1–4 hours as needed 1
- Incomplete response (PEF 50–75% predicted): Continue intensive treatment every 1–2 hours; consider hospital admission 1
- Poor response (PEF <50% predicted): Increase frequency to every 15–30 minutes or switch to continuous nebulization; arrange immediate hospital admission 1, 2
Life-Threatening Features Requiring Immediate Escalation
Transfer immediately to emergency department if any of the following are present: 1, 2
- PEF <33% predicted
- Silent chest, cyanosis, or feeble respiratory effort
- Altered mental status (confusion, drowsiness, exhaustion)
- Bradycardia or hypotension
- Normal or elevated PaCO₂ ≥42 mmHg in a breathless patient
Critical Pitfalls to Avoid
Never administer sedatives to patients with acute asthma—this is absolutely contraindicated. 1, 2
Do not underestimate severity—objective PEF/FEV₁ measurement is mandatory; failure to obtain objective measurements is the most common preventable cause of asthma death. 1, 2
Do not use only 2 puffs as recommended for stable asthma maintenance—this dose is inadequate for acute exacerbations. 2, 3
Ensure proper spacer use—failure to use a spacer dramatically reduces drug delivery, and improper technique (actuating multiple puffs into the spacer at once) significantly decreases lung deposition. 2, 4, 7
Special Populations
Children <4 years: Use valved holding chamber with face mask; same 4–8 puff dosing applies. 1, 4 For children weighing <15 kg, consider using the lower end of the dosing range (4 puffs) initially. 1
Severe refractory cases: Consider intravenous magnesium sulfate 2 g over 20 minutes for life-threatening features or severe exacerbations not responding after 1 hour of intensive treatment. 1, 2