Glycopyrrolate
Glycopyrrolate
Generic Name
Glycopyrrolate
Mechanism
Glycopyrrolate is a quaternary ammonium antimuscarinic that *competitively blocks* muscarinic acetylcholine receptors (M1‑M5).
• Peripheral selectivity: Cannot cross the blood‑brain barrier, minimizing central anticholinergic toxicity.
• Effect on smooth muscle & glands: Inhibits secretions (saliva, gastric acid, bronchial mucus) and relaxes gastrointestinal and airway smooth muscle.
• Clinical consequence: Reduced secretions during anesthesia, slower gastric motility (used for postoperative nausea), and decreased reflexive airway responses.
Pharmacokinetics
- Absorption
- Oral: 10‑20 % bioavailability; peak plasma ∼30–60 min.
- Intravenous: 100 % bioavailability, onset 1–2 min.
- Distribution
- Plasma protein binding: ~10 %.
- Volume of distribution: ~1 L/kg.
- Metabolism
- Not metabolized; unchanged throughout elimination.
- Elimination
- Renal excretion: 80 % unchanged in urine.
- Half‑life: 12–15 h (adult), 18–22 h (elderly).
- Clearance: ~8 mL min⁻¹ kg⁻¹.
- Drug interactions
- Renal impairment reduces clearance → ↑ exposure.
- Co‑administration with other anticholinergics enhances toxicity.
- No significant CYP450 interactions.
Indications
- Pre‑operative anticholinergic: ↓ salivary and bronchial secretions, minimize aspiration risk.
- Post‑operative nausea & vomiting (PONV): Parenteral infusion reduces gastric secretions and motility.
- Peptic ulcer disease & GERD: Oral therapy reduces acid secretion.
- Chronic cough & upper airway disorders: Needs to reduce mucus production.
- Salivary hypersecretion: Used in dental procedures or xerostomia management.
- Gastroparesis & colonic spasm: In some protocols for prokinetic management.
Contraindications
- Absolute contraindications
- Occlusive GI/urinary tract (e.g., intestinal obstruction, severe urinary retention).
- Ocular conditions: narrow‑angle glaucoma.
- Myasthenia gravis, acute heart failure, or severe cardiac arrhythmias.
- Relative contraindications
- Concomitant use of β‑blockers or anti‑arrhythmics.
- Pregnancy: Category C → use only if benefit outweighs risk.
- Elderly or renal impairment: monitor closely.
- Warnings
- Anticholinergic toxicity: dry mouth, blurred vision, tachycardia, urinary retention, constipation, delirium.
- Hypersensitivity/steroidal rash.
Dosing
| Patient | Form | Typical Dose | Frequency | Notes |
| Adults – Oral | PO | 0.2–0.4 mg | Every 4–6 h | Adjust downward if renal disease. |
| Adults – IV (pre‑op) | IV | 0.2 mg | Single bolus 10 min before induction | Re‑dose 0.2 mg after if needed. |
| Adults – IV (PONV) | IV | 0.2 mg | Continuous infusion 0.2 mg/h for 30 min post‑op | Use as part of multimodal PONV prophylaxis. |
| Pediatric (≤12 y) | IV | 0.02 mg/kg | 10 min before procedure | Max 0.2 mg. |
| Pediatric (12‑18 y) | IV | 0.1 mg | 10 min before procedure | 0.2 mg max. |
| Elderly (>75 y) or renal impairment | PO/IV | 0.1–0.2 mg | Every 4–6 h (PO) | Monitor for prolonged action. |
*Adjust based on clinical response and side‑effect profile.*
Adverse Effects
- Common
- Dry mouth, blurred vision, constipation, urinary retention.
- Tachycardia, increased heart rate.
- Decreased bowel motility → intestinal stasis.
- Serious
- Anticholinergic crisis (hyperthermia, seizures, delirium).
- Severe hypotension or arrhythmias (especially in heart disease).
- Pulmonary edema or acute respiratory distress (very rare).
Monitoring
- Vital signs: BP, pulse, respiratory rate (baseline + 15‑30 min post‑dose).
- Cardiac: ECG in patients with arrhythmia or on β‑blockers.
- Renal function: Serum creatinine & eGFR 48 h after initiating therapy if on chronic dose.
- Neurological: Assess for confusion or agitation.
- Urinary output: >0.5 mL/kg/h to avoid retention.
Clinical Pearls
- No CNS side‑effects: Glycopyrrolate’s quaternary ammonium structure prevents CNS penetration, making it preferable to atropine when central toxicity is a concern.
- Long half‑life: Effective for overnight PONV prophylaxis; may shorten sedation time in intensive care.
- Dry‑mouth hazard: Important in patients on other anticholinergics; encourage sips of water intra‑operatively.
- Spot dosing: For emergent airway secretions, 0.1–0.2 mg IV is usually sufficient; avoid excessive doses to limit urinary retention.
- Renal adjustment: In CKD stage 4–5, urinary retention risk rises; consider 0.05‑0.1 mg PO q8 h or discontinue.
- Drug synergy: When combined with succinylcholine, glycopyrrolate mitigates fasciculations but can amplify sludging atmospheric secretions if used too early.
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• *This drug card provides a concise, high‑yield overview of glycopyrrolate for students and clinicians. For detailed dosing protocols, always consult the latest product labeling or institutional guidelines.*