Generic Name

Ipratropium

Mechanism

Ipratropium is a short‑acting, competitive antagonist of muscarinic acetylcholine receptors, primarily the M3 subtype on airway smooth muscle. By blocking these receptors, it prevents acetylcholine‑induced bronchoconstriction, thus facilitating bronchodilation. The drug does not act on β2‑adrenergic receptors, making it complementary to β‑agonists. It is inactivated by carbamate hydrolysis in the tissue and excreted unchanged by the kidneys.

Pharmacokinetics

• Absorption: Rapid pulmonary absorption following inhalation; systemic bioavailability is <1 %.
• Distribution: Limited systemic spread; peak plasma concentration occurs within 10 – 30 min.
• Metabolism: Hydrolyzed to an inactive metabolite by carboxylesterases; minimal hepatic involvement.
• Excretion: Mainly renal (≈70 % unchanged); half‑life in plasma 2 – 3 h.
• Special Populations: Renal impairment prolongs systemic clearance; adjust therapy accordingly.

Indications

• Chronic Obstructive Pulmonary Disease (COPD) exacerbations and maintenance therapy.
• Asthma management, particularly in patients with reversible bronchoconstriction.
• Adjunctive therapy with β‑agonists for acute bronchospasm.

Contraindications

• Contraindications:
• Urinary retention.
• Mechanical obstruction of the bronchial tract.
• Warnings:
• Ocular disorders (glaucoma, cataract surgery).
• Pregnancy: Category B – use only if benefits outweigh risks.
• Children <6 yr: not recommended due to limited data.

Dosing

Maximum daily dose: 800 µg per day (MDI) or 36 µg per day (DPi).

Adverse Effects

Common
• Dry mouth, dysphonia, cough, throat irritation.
• Paradoxical bronchospasm (rare).

Serious
• Severe hypotension or bradycardia (unlikely with inhaled route).
• Ocular irritation, angle‑closure glaucoma (in susceptible individuals).
• Hepatic dysfunction (rare, monitor LFTs when co‑administered with hepatotoxic drugs).

Monitoring

• Peak expiratory flow (PEF) or FEV1 in COPD patients.
• Adherence and inhaler technique.
• Ocular pressure in patients with glaucoma history.
• Serum creatinine if renal function is borderline.

Clinical Pearls

• Inhalation Technique is Key: A poor spacer or dry powder technique significantly reduces drug delivery; teach patients to exhale fully before each puff.
• Use as an Adjunct: Combining ipratropium with albuterol yields superior bronchodilation, especially in acute exacerbations.
• Carbamate Hydrolysis: The drug’s rapid hydrolysis limits systemic exposure—explains its relatively low side‑effect profile compared to oral anticholinergics.
• Dose Titration in COPD: Start at the lowest effective dose (2 puffs) and increase only if symptoms persist after 4 – 6 weeks; this reduces dry‑mouth complaints while maintaining efficacy.
• Nebulizer Use in Severe COPD: Nebulized ipratropium is preferable when patients cannot coordinate MDI technique—especially in post‑extubation COPD exacerbation.
• Contraindications in Urinary Tract: In patients with bladder outlet obstruction, alternative bronchodilators should be considered to avoid exacerbated retention.

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