Ventolin HFA
Ventolin HFA
Generic Name
Ventolin HFA
Mechanism
- Selective β₂‑adrenergic stimulation in airway smooth muscle → cAMP ↑ → protein kinase A activation → phosphorylation of myosin light‑chain kinase → relaxation.
- Rapid onset (≤5 min) and short duration (≈4–6 h) due to rapid receptor desensitization and drug clearance.
Pharmacokinetics
| Parameter | Typical Value (oral/sublingual – not recommended) |
| Absorption | Immediate after pulmonary delivery; 95 % bioavailability via inhalation. |
| Distribution | Volume of distribution ≈ 5 L /m²; highly lipophilic. |
| Metabolism | Liver (cytochrome P450 3A4) → active sulfate conjugate. |
| Elimination | Renal excretion; half‑life ≈ 4 h (inhaled). |
> *Note:* Systemic absorption is low with standard inhalation, but higher doses (≥ 30 µg) can cause measurable plasma levels.
Indications
- Acute relief of bronchospasm in asthma.
- Emergency treatment of acute exacerbations of COPD.
- Used as a rapid‑onset rescue inhaler; not for long‑term maintenance.
Contraindications
- Contraindications: Severe cardiac arrhythmia, severe hypotension, uncontrolled tachycardia, known hypersensitivity to β‑agonists.
- Warnings:
- Use with caution in patients with cardiovascular disease: potential for tachycardia, palpitations, QT prolongation.
- May mask worsening asthma or COPD if used excessively; monitor for “rebound” symptoms.
- Pregnancy category: C; use only when benefits outweigh risks.
Dosing
| Population | Dose | Frequency | Route | Notes |
| Adults/Adolescents | 2–4 puffs per actuation (30 µg) | Every 4–6 h as needed | MDI or Diskus® | Do not exceed 12 puffs per day (360 µg). |
| Children (≥12 y) | 1–2 puffs | Every 4–6 h | MDI | Careful with dose; peak bronchodilation 5–10 min. |
| Children (5–11 y) | 1 puff | Every 4–6 h | MDI | Use spacer for optimal deposition. |
| Infants/Young Children | 1/2 puff | Every 4–6 h | MDI | Spacer or nebulizer may be preferable. |
• Technique: Shake, prime, inhale slowly while exhaling, hold breath 5 s, then repeat if needed.
• Reconstitution: Never mix with other solutions; keep in original plastic tube to prevent degradation.
Monitoring
- Vital signs: heart rate, blood pressure, ECG if tachycardia risk.
- Serum potassium: baseline and repeat when high‑dose is used.
- Respiratory: peak expiratory flow rate (PEFR) ≥ 80 % predicted as a response marker.
- Adherence & technique: periodic review to prevent over‑use.
Clinical Pearls
- Spacer use cuts systemic side‑effects by up to 50 %—essential for children and patients with poor inhaler technique.
- Dose‑sparingly: Rescue inhalers are for acute symptoms; if “over‑use” (> 12 puffs/day) is frequent, refer for asthma control review.
- Rebound asthma: The 4–6 h window may precipitate a “rebound” bronchospasm if the drug is stopped abruptly; advise gradual tapering if long‑term use is anticipated.
- Contra‑indications in pregnancy: Use only in life‐threatening asthma or COPD; counsel on risks versus benefits.
- Drug interactions: β₂‑agonists potentiate the cardiovascular effects of catecholamines and monoamine oxidase inhibitors—avoid concurrent use unless monitored.
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• *Prepared for medical students and practising clinicians – reference‑ready with key pharmacological highlights and practical dosing details.*