Xopenex HFA
Xopenex HFA
Generic Name
Xopenex HFA
Mechanism
- β₂‑adrenergic agonist: Selective stimulation of β₂‑adrenergic receptors on airway smooth muscle.
- cAMP cascade activation: β₂ stimulation → adenylyl‑cyclase ↑ → cyclic AMP ↑ → protein kinase A (PKA) activation.
- Vesicular chloride secretion & smooth‑muscle relaxation: PKA phosphorylates L-type Ca²⁺ channels and myosin light‑chain kinase → ↓ intracellular Ca²⁺, leading to bronchodilation.
- Additional effects: Inhibits inflammatory mediator release from mast cells and eosinophils, and reduces mucus secretion.
Pharmacokinetics
| Parameter | Typical Value | Comments |
| Absorption | Rapid pulmonary absorption; <1 % reaches systemic circulation via the inhaled dose. | Most drug exerts action locally. |
| Distribution | Extensive tissue distribution, high lipid solubility. | Pulmonary and systemic β₂ sites. |
| Metabolism | Hydrolyzed by hepatic esterases; conjugated (glucuronidation) in the liver. | Short half‑life due to rapid clearance. |
| Half‑life | ~4 h (inhaled); systemic <3 h. | Supports short‑acting profile. |
| Excretion | Renal (~50%), biliary (~30%), residual exhaled. | No accumulation with intermittent use. |
Indications
- Acute bronchospasm (asthma, COPD) – rescue inhaler.
- Pre‑exercise bronchodilation for patients with exercise‑induced bronchospasm.
- Emergency treatment of acute asthma attack (when delivered via nebulizer or MDI).
Contraindications
- Contraindications: Severe hypotension, uncontrolled cardiac arrhythmias, concurrent use of beta‑agonist antiarrhythmics.
- Warnings:
- Cardiac: May precipitate tachycardia, palpitations, arrhythmias.
- Metabolic: Hyperglycemia in diabetic patients.
- CNS: Anxiety, tremor, tremulousness.
Dosing
*Standard adult dosing (MDI 200 µg per actuation).*
| Condition | Dose | Frequency | Notes |
| Acute bronchospasm | 2–4 puffs (800–1 600 µg) every 15 min up to 4 puffs | Max 30 puffs in 24 h | Use spacer if coordination difficult. |
| Exercise‑induced | 1–2 puffs 15 min before exercise | Once nightly in the evening | Continue rescue dosing as needed. |
| Maintenance | *Not indicated* | — | Use as prescribed for rescue, not chronic. |
• Spacers: Reduce oral deposition and improve lung deposition.
• Nebulisation: For patients unable to use MDI; 0.05 mg/mL salbutamol, 4–5 mL per dose.
Adverse Effects
- Common: Tremor, palpitations, tachycardia, headache, throat irritation, coughing.
- Serious (rare): Severe arrhythmias, significant electrolyte disturbances, paradoxical bronchoconstriction (especially with inappropriate use).
- Allergic reactions: Rash, pruritus, anaphylaxis (extremely rare).
Monitoring
- Respiratory: Peak expiratory flow (PEF) or spirometry baseline & post‑dose.
- Cardiac: Pulse, blood pressure, ECG in patients with cardiac risk.
- Metabolic: Blood glucose in diabetics; electrolyte panel if prolonged use.
- Drug compliance: Metered‑dose counter checks; adherence counseling.
Clinical Pearls
- Use a spacer: Improves delivery to lower airways, especially in children or during an acute attack.
- Avoid over‑use: >30 puffs/day → risk of systemic effects and tachyphylaxis.
- Spiracular use: A single rescue puff (200 µg) can relieve mild symptoms; reserve multiple puffs for moderate‑severe exacerbations.
- Exercise timing: Administer 15 min before activity; for athletes, a single dose suffices.
- Check drug synergy: β₂‑agonists and inhaled corticosteroids should be used together for optimal outcome; Xopenex alone is not suitable for chronic control.
- Contraindication vigilance: A patient with recent myocardial infarction may experience arrhythmia; evaluate cardiac status before initiating therapy.
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• *This drug card is intended for educational use and does not replace individualized medical judgment or official prescribing guidelines.*