Xopenex
Xopenex
Generic Name
Xopenex
Mechanism
- Selective activation of β₂‑adrenergic receptors on airway smooth muscle.
- Receptor stimulation triggers the Gs protein → ↑ adenylate cyclase → ↑ cyclic‑AMP.
- cAMP activates protein kinase A → phosphorylation of myosin light‑chain kinase → relaxation of smooth muscle.
- Rapid onset (< 5 min) and brief duration (~ 4–6 h).
Pharmacokinetics
| Parameter | Value |
| Absorption | Pulmonary delivery → > 80 % bioavailability; negligible oral absorption. |
| Onset | 3–5 min (nebulizer) |
| Peak effect | 15–30 min |
| Duration | 4–6 h |
| Metabolism | Hepatic via CYP3A4 → inactive metabolites. |
| Elimination | Renal (≈ 70 %) & hepatic (≈ 30 %). |
| Half‑life | 4–5 h (systemic exposure). |
> Tip: Nebulized administration bypasses first‑pass metabolism, providing rapid relief with lower systemic exposure.
Indications
- Acute asthma exacerbation (rescue bronchodilation).
- Acute COPD flare‑up (rescue bronchodilation).
- Pre‑operative bronchodilation for patients with reactive airway disease.
Contraindications
- Absolute contraindication: Severe hypotension or profound bradycardia.
- Relative contraindications:
- Known hypersensitivity to the drug or excipients.
- History of myocardial infarction within 6 months.
- Warnings:
- Cardiac arrhythmias, ischemia, hypertension.
- Serum potassium depletion, especially in patients on diuretics or steroids.
- Overdose → hepatic toxicity (rare).
Dosing
Nebulized Solution (recommended for acute episodes)
| Age Group | Dose | Frequency | Notes |
| Adults & adolescents (≥ 12 yrs) | 2.5 mg (in 5–10 mL NaCl 0.9 %) | 5–30 min, repeat every 20–30 min up to 4 doses | Use breath‑hold technique. |
| Children (2 – 11 yrs) | 1.25 mg | Same as above | Adjust volume per weight. |
| Infants (< 2 yrs) | 0.5 mg | Same | Primarily used with nebulizer; monitor carefully. |
Prophylactic Administration (once daily in high‑risk chronic users)
• 120 mg oral capsule (if formulation available).
• Adjunct to inhaled corticosteroids for stable COPD.
Monitoring
- Vital signs: HR, BP & SpO₂ continuously during acute administration.
- Pulse oximetry & capnography during nebulization.
- Serum potassium if on diuretics, steroids, or antidiuretic therapy.
- Liver function tests if repeated daily dosing > 7 days.
Clinical Pearls
- Breath‑hold maneuver: Encourage patients to hold breath for 10 s post‑inhalation for maximal drug deposition.
- Avoid sudden positional changes immediately after inhalation to mitigate hypotension.
- Combine with systemic steroids in moderate‑severe exacerbations for synergistic benefit.
- Re‑dose safely: If symptoms recur within 60 min, a second dose is safe; a third may be considered after 24 h of symptom control.
- Patient education: Stress adherence to prescribed inhaler technique & regular monitoring for cardiac symptoms.
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• Xopenex remains a frontline rescue bronchodilator, providing rapid relief from bronchospasm with a well‑characterized safety profile. Its targeted β₂‑selectivity minimizes cardiac β₁‑mediated side effects, making it suitable for the vast majority of acute asthmatic and COPD presentations.