ProAir HFA
ProAir HFA
Generic Name
ProAir HFA
Mechanism
ProAir HFA delivers the short‑acting sympathomimetic bronchodilator albuterol (salbutamol) via a metered‑dose inhaler.
* Albuterol binds selectively to β₂‑adrenergic receptors on bronchial smooth‑muscle.
* Activation of the receptor stimulates Gs protein → adenylyl cyclase → ↑cAMP → activation of protein kinase A → phosphorylation of ion channels and phospholipase.
* The net result is relaxation of airway smooth muscle, dilation of the bronchi, and fast relief of bronchospasm.
* The drug also exhibits modest vasodilation and minimal systemic effects at therapeutic doses.
Pharmacokinetics
| Parameter | Description |
| Absorption | Rapid lung deposition; systemic absorption ~10–15 % of inhaled dose. |
| Onset | 2–5 min; peak bronchodilation at 5–10 min. |
| Half‑life | Plasma ~4–6 h; airway activity lasts 4–6 h. |
| Distribution | Widely distributed via lung and peripheral tissues; protein binding ~5 %. |
| Metabolism | Oxidative deamination to inactive metabolites. |
| Excretion | Renal (~70 %) and urinary (~20 %) excretion. |
| Cautions | Renal impairment may prolong plasma concentration slightly; no dose adjustment needed. |
Indications
* Acute asthma exacerbations – rescue bronchodilation.
* Chronic obstructive pulmonary disease (COPD) – relief of acute bronchospasm.
* Exercise‑induced bronchospasm – pre‑exercise administration.
* Pre‑operative management of bronchoconstriction in at‑risk patients.
Contraindications
| Category | Detail |
| Contraindications | Hypersensitivity to albuterol or any inhaler component; severe uncontrolled tachyarrhythmias (e.g., atrial fibrillation > 140 bpm). |
| Warnings | *Cardiovascular:* significant tachycardia, palpitations, hypertension. *Pulmonary:* paradoxical bronchospasm. |
| Precautions | Use with caution in diabetes (glucose metabolism changes), thyrotoxicosis, and neuroleptic medication usage. |
| Drug Interactions | Caution when combined with other β₂‑agonists, propranolol (non‑selective β‑blocker), or high‑dose methylxanthines (e.g., theophylline) due to potential synergistic cardiac effects. |
Dosing
* Age ≥ 6 yrs: 2–4 puffs per inhalation (≈ 90–180 µg per puff).
* Maximum daily dose: Up to 12 puffs (≈ 1 200 µg) over 24 h unless otherwise directed.
* Administration: Hold breath for 5–10 s after each puff; repeat if symptoms persist.
* Asthma attack: 1–4 puffs every 20 min for the first 2 h, then reduce as symptoms improve.
* Pre‑operative: 30–60 min before surgery to mitigate peri‑operative bronchospasm.
* Special populations: Pediatric < 6 yrs – < 2 puffs; geriatric – follow standard dosing unless adverse events occur.
Adverse Effects
| Common (≥ 1 %) | Serious (≤ 1 %) |
| Tremor | Anaphylaxis |
| Palpitations | Severe cardiac arrhythmias |
| Headache | Hypotension |
| Ataxia | Paradoxical bronchospasm |
| Palpitations, tachycardia | Severe hyperglycemia (rare) |
| Dry mouth | Severe bronchoconstriction refractory to therapy |
Monitoring
* Vital signs – heart rate, blood pressure, O₂ saturation during and after rescue doses.
* Peak expiratory flow (PEF) or spirometry in outpatient settings.
* Blood glucose if patient is diabetic and on rescue β₂‑agonist.
* Symptom diary for early detection of paradoxical bronchospasm.
Clinical Pearls
1. Inhaler Technique Matters – Instruct patients to rinse mouth after each use to reduce candidiasis risk and to ensure proper deposition.
2. First‑Dose Watch – The first inhalation often produces the largest systemic effect; monitor vitals during initial use in high‑risk patients.
3. Avoid β₂‑blocking Medications – Non‑selective β‑blockers (e.g., propranolol) blunt bronchodilation and should be avoided; if needed, use inhaled selective β₁‑blockers with caution.
4. Safe Combination with Systemic Steroids – Supportive rescue therapy can be safely paired with oral/IV corticosteroids; no dose adjustment needed.
5. Dose‑Escalation Strategy – If symptoms persist after 4 puffs, increase to 8 puffs only if not exceeding the 12‑puff limit; do not exceed more than 12 puffs in 24 h without medical review.
--
• ProAir HFA remains a cornerstone for rapid relief of bronchospasm, offering fast onset and ease of use for both patients and caregivers in acute settings.