Salbutamol inhalers

Generic Name: Salbutamol (INN)
United States Adopted Name (USAN): Albuterol
Common Brand Names: Ventolin, ProAir, Proventil, Airomir, Salamol
Drug Class: Short-Acting Beta-2 Adrenergic Receptor Agonist (SABA)
Formulations Available:

• Metered-Dose Inhaler (MDI): 100 micrograms (mcg) per actuation

• Dry Powder Inhaler (DPI): e.g., Accuhaler/Diskus 200 mcg per dose

• Nebulizer Solution: 2.5 mg/2.5 mL, 5 mg/2.5 mL

• Oral forms and injectable forms exist but are not first-line

Route of Administration: Inhaled (oral via MDI, DPI, or nebulization)

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Approved Therapeutic Indications

Salbutamol inhalers are first-line agents for rapid relief of bronchospasm in various respiratory disorders. They are not designed for long-term disease control but for acute symptom relief.

Primary Indications:

1. Asthma

   • Relief of acute asthma symptoms (wheezing, breathlessness)

   • Prevention of exercise-induced bronchospasm (EIB)

   • Management of exacerbations in children and adults

   • As-needed use in mild intermittent asthma

   • Rescue therapy in moderate to severe asthma

2. Chronic Obstructive Pulmonary Disease (COPD)

   • Relief of reversible bronchospasm

   • Acute symptom relief or pre-exercise use in combination with maintenance therapy

3. Exercise-Induced Bronchoconstriction (EIB)

   • Used 15–30 minutes before exercise to prevent bronchospasm

4. Anaphylaxis/Severe Allergic Reactions (adjunctive)

   • For bronchospasm when intramuscular epinephrine is not sufficient

5. Hyperkalemia (off-label, nebulized form)

   • Facilitates potassium uptake into cells via β2 receptor stimulation

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Mechanism of Action

Salbutamol is a selective β2-adrenergic receptor agonist that primarily targets receptors in bronchial smooth muscle.

Primary Pharmacological Effects:

• Stimulates adenylate cyclase → increases intracellular cAMP

• Activates protein kinase A → inhibits phosphorylation of myosin and reduces intracellular calcium

• Result: relaxation of bronchial smooth muscle → bronchodilation

Secondary Effects:

• Enhances mucociliary clearance

• Mild vasodilation in bronchial vessels

• Promotes movement of potassium into cells (basis for hyperkalemia management)

Onset and Duration:

• Inhaled: onset within 5 minutes, peak at ~30 minutes, duration ~4 hours

• Nebulized: faster systemic absorption, greater side effect risk

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Dosage and Administration

Inhaled (MDI or DPI):

Adults and Children ≥4 years:

• Acute relief: 100–200 mcg (1–2 puffs) every 4–6 hours as needed

• Pre-exercise (EIB): 200 mcg 15–30 minutes before activity

• Max dose: Generally up to 800 mcg/day (4 doses), higher under medical supervision during exacerbations

Children <4 years:

• Not typically MDI; use spacer or nebulizer

• Consult pediatric respiratory protocol

Nebulized Solution:

• 2.5–5 mg every 4–6 hours

• Severe exacerbations: every 20 minutes for 3 doses, then PRN

Spacer Devices:

• Highly recommended, especially in children and the elderly

• Improve drug delivery and reduce oropharyngeal deposition

Important:

• Always rinse mouth after use to prevent irritation

• Shake inhaler before use (if MDI)

• Prime inhaler before first use or if not used for ≥2 weeks

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Pharmacokinetics

• Absorption: Rapid via lungs, minimal oral systemic absorption (via swallowed fraction)

• Bioavailability (inhaled): 10–20% reaches lungs

• Metabolism: Hepatic via sulfation

• Half-life: 3–6 hours

• Excretion: Renal (primarily as metabolites), ~80–90% in urine

• Onset: <5 minutes

• Peak effect: 30 minutes

• Duration of action: 4–6 hours

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Contraindications

• Hypersensitivity to salbutamol or any excipient in the inhaler

• Severe tachyarrhythmias not related to reversible airway disease

• Use in labor to delay delivery (tocolysis) is contraindicated in some regions due to cardiovascular risks

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Precautions and Warnings

1. Paradoxical bronchospasm: Rare but life-threatening; discontinue immediately

2. Frequent use as rescue therapy: Suggests poor asthma control – reevaluate maintenance therapy

3. Cardiovascular risks: Use cautiously in patients with cardiac arrhythmias, hypertension, or ischemic heart disease

4. Hypokalemia: β2 stimulation promotes intracellular potassium shift

5. Hyperglycemia: Especially in high doses

6. Seizures: Rare neurological adverse effects reported

7. Overuse leading to tolerance: May reduce efficacy over time

8. Pregnancy and Lactation: Considered generally safe; use only if benefit outweighs potential risk

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Adverse Effects

Common (1–10%):

• Tremor (hands, especially in elderly or high doses)

• Palpitations

• Tachycardia

• Nervousness or restlessness

• Headache

• Muscle cramps

Less Common (<1%):

• Nausea

• Chest pain

• Dizziness

• Hypokalemia

• Insomnia

• Paradoxical bronchospasm

Rare/Serious:

• Cardiac arrhythmias

• Severe hypokalemia

• Anaphylaxis

• Hyperactivity in children

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Drug Interactions

1. Non-selective β-blockers (e.g., propranolol):

   • Antagonize bronchodilation effect; contraindicated in asthma

2. Diuretics (loop and thiazide):

   • May enhance hypokalemia

3. MAO inhibitors and tricyclic antidepressants:

   • Potentiate cardiovascular side effects; avoid co-use

4. Digoxin:

   • May decrease serum levels; monitor effectiveness

5. Other sympathomimetics (e.g., epinephrine):

   • Additive cardiovascular effects

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Monitoring Parameters

• Clinical symptom relief (cough, wheezing, dyspnea)

• Frequency of use (excessive reliance indicates uncontrolled disease)

• Heart rate and rhythm

• Serum potassium in high-dose use or with diuretics

• Inhaler technique (regular reassessment recommended)

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Comparative Notes

Medication	Class	Onset	Duration	Use
Salbutamol	SABA	~5 mins	~4–6 hrs	Acute relief (rescue)
Formoterol	LABA	~3 mins	~12 hrs	Maintenance + rapid relief
Salmeterol	LABA	~10–20 min	~12 hrs	Maintenance only (no rescue)

Salbutamol is not suitable as monotherapy for persistent asthma or as a maintenance drug in COPD. Long-term controller medications (inhaled corticosteroids, LABAs, LAMAs) must be considered.

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Patient Counseling Points

• Use only as needed for symptom relief or before exercise

• Inform healthcare provider if you need the inhaler more than twice weekly

• Shake well before each use (if MDI)

• Rinse mouth after inhalation to prevent throat irritation

• Clean spacer/inhaler regularly as per manufacturer instructions

• Keep track of inhaler doses if using a dose counter

• Inform provider of side effects like tremors, heart racing, or chest discomfort

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Storage and Stability

• Store at room temperature (15–25°C)

• Keep away from heat and direct sunlight

• Avoid freezing

• Do not puncture or incinerate pressurized canisters

• Check expiry and number of doses remaining if device has counter

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Availability and Regulation

• Prescription status:

  • UK, US, EU: Prescription-only

  • In some regions, may be OTC in low-dose forms

• Global brands:

  • Ventolin (GSK)

  • ProAir, Proventil (US)

  • Salamol, Airomir

• Combination products:

• Salbutamol + ipratropium (Combivent)

• Salbutamol + corticosteroids (less common, not preferred)