EpistemisTiotropium Bromide, Glycopyrronium, Aclidinium and Umeclidinium
LAMAs are the first-line bronchodilators in the maintenance treatment of COPD (Group A, B and E of the GOLD guide) and in severe asthma (GINA 5). Its molecular design pursues kinetic selectivity on the M3 receptor.
Pharmacokinetics
Mechanism of action and kinetic selectivity
Unlike ipratropium, LAMAs demonstrate high kinetic selectivity for the muscarinic M1 and M3 receptors compared to the presynaptic M2 receptor:
- Kinetic selectivity mechanism: LAMAs initially bind and block all three receptor subtypes, but dissociate at dramatically different rates. The dissociation constant for the M2 receptor is extremely fast (t1/2 dissociation < 4 hours), while the dissociation for the M3 receptor is slow (t1/2 dissociation for tiotropium from the M3 receptor > 35 hours).
- Functional impact: This allows the contractile pathway (M3) to be blocked throughout the day (24 hours) without altering presynaptic negative autoregulation (M2), preventing the escape of acetylcholine into the synaptic cleft.
Prevention of Exacerbations by LAMA in COPD
Large-scale clinical trials (such as the UPLIFT study with tiotropium) demonstrated that LAMAs are superior to LABAs in reducing COPD exacerbations. This is because chronic cholinergic inhibition reduces the volume of mucous secretions and their viscosity, improves mucociliary clearance and decreases dynamic air trapping (hyperinflation), breaking the vicious cycle of dyspnea and infection.
Pharmacokinetics
| Parameter | Tiotropium bromide | Glycopyrronium | Aclidinium bromide | Umeclidinium |
|---|---|---|---|---|
| Device | HandiHaler (DPI) or Respimat (SMI) | Breezhaler (DPI) | Genuair (DPI) | Ellipta (DPI) |
| Systemic bioavailability | ~20% (Respimat) / ~30% (pulmonary absorption) | ~45% (high lung absorption) | <5% (due to rapid plasma metabolism) | ~13% |
| Dissociation half-life M3 | ~35 - 37 hours | ~20 - 24 hours | ~10 - 15 hours | >80 hours (long association) |
| Metabolism | Hepatic minimum (CYP2D6 and CYP3A4) | Mainly hydroxylation via CYP2D6 | Rapid hydrolysis by plasma esterases (minimizes RAMs) | Hepatic extensive by CYP2D6 |
| Excretion | Renal (74% as unchanged drug) | Renal (85% of the absorbed fraction) | Renal (as inactive hydrolyzed metabolites) | Renal and fecal |
Indicators and dose
Dosage and Clinical Adjustment
Adults:
- Tiotropium Respimat: 2 inhalations of 2.5 µg once a day (total daily dose of 5 µg).
- Aclidinium Genuair: 1 inhalation of 322 µg every 12 hours (due to its rapid systemic enzymatic plasma clearance).
- Umeclidinium Ellipta: 1 inhalation of 55 µg once a day.
Adjustment in Renal Insufficiency: Since tiotropium and glycopyrronium are predominantly excreted renally, in patients with moderate to severe renal insufficiency (creatinine clearance < 50 mL/min or eGFR < 30 mL/min) the appearance of systemic anticholinergic side effects should be closely monitored. The clearance of aclidinium is not affected by renal dysfunction as it is rapidly hydrolyzed in plasma.
Security
Adverse effects (ADRs)
- Xerostomia (Dry mouth): The most characteristic and common adverse effect due to salivary cholinergic blockade (≈ 10% - 15%).
- Constipation and mild dysuria.
- Atrial fibrillation and tachyarrhythmias: Close caution in elderly patients with active structural or severe ischemic cardiovascular disease.
Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.
- System
- Respiratory
- Cluster
- Long-Acting Muscarinic Antagonists (LAMA)