GLYCOPYRROLATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GLYCOPYRROLATE (GLYCOPYRROLATE).
Glycopyrrolate is a quaternary ammonium anticholinergic agent that competitively antagonizes acetylcholine at muscarinic receptors in the autonomic nervous system, thereby reducing salivary, gastric, and bronchial secretions. It also exhibits antispasmodic effects on gastrointestinal smooth muscle.
| Metabolism | Glycopyrrolate is minimally metabolized, primarily excreted unchanged in urine and bile. Hepatic metabolism is negligible. It is not a substrate for CYP450 enzymes. |
| Excretion | Primarily renal excretion of unchanged drug (85-90%) with biliary/fecal elimination accounting for <10%. |
| Half-life | Terminal elimination half-life: 0.6-1.2 hours (IM/IV), with prolonged duration in elderly and renal impairment. |
| Protein binding | ~50% bound, primarily to albumin. |
| Volume of Distribution | 0.4-0.6 L/kg, indicating moderate distribution mainly in extracellular fluid. |
| Bioavailability | IM: ~90%; Oral: <10% due to extensive first-pass metabolism; IV: 100%. |
| Onset of Action | IV: ~1 minute; IM: 10-20 minutes; Oral: not used systemically (poor absorption). |
| Duration of Action | IV/IM: 4-6 hours for antisecretory effects; longer for vagal blockade (up to 8 hours). |
1-2 mg orally 2-3 times daily; maximum 8 mg/day. For parenteral use: 0.1-0.2 mg IV/IM every 4-6 hours as needed.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment guidelines. Use with caution in severe renal impairment (CrCl <30 mL/min) due to potential accumulation; consider dose reduction and monitoring. |
| Liver impairment | No specific dose adjustment guidelines for Child-Pugh classification. Use with caution in severe hepatic impairment due to potential prolonged effects. |
| Pediatric use | For intraoperative use: 0.004 mg/kg IV/IM, not to exceed 0.1 mg. For peptic ulcer: 0.5-1 mg orally every 12 hours; maximum 3 mg/day. Weight-based dosing preferred. |
| Geriatric use | Elderly patients may be more sensitive to anticholinergic effects; initiate at lower dose (e.g., 0.5-1 mg orally twice daily) and titrate gradually. Monitor for confusion, urinary retention, and constipation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GLYCOPYRROLATE (GLYCOPYRROLATE).
| Breastfeeding | Unknown if excreted in human milk; M/P ratio not available. Use with caution due to potential anticholinergic effects in infant. |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: No known fetal harm; may cause tachycardia and decreased GI motility in neonate if used near term. Risk Category B per FDA. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to glycopyrrolate or any component of the formulation.","Narrow-angle glaucoma.","Obstructive uropathy (e.g., prostatic hypertrophy causing urinary retention).","Gastrointestinal obstruction (e.g., pyloric stenosis, paralytic ileus).","Severe ulcerative colitis or toxic megacolon.","Myasthenia gravis (unless used for specific anticholinesterase reversal)."]
| Precautions | ["May precipitate angle-closure glaucoma in patients with narrow angles.","May cause urinary retention, especially in patients with prostatic hypertrophy or bladder obstruction.","May increase heart rate and should be used with caution in patients with tachyarrhythmias or other cardiac conditions.","May reduce gastrointestinal motility leading to ileus in postoperative patients or those with intestinal obstruction.","Anticholinergic effects may be potentiated in hot environments (risk of hyperthermia).","Use cautiously in patients with myasthenia gravis due to potential worsening of muscle weakness."] |
| Food/Dietary | No significant food interactions known. However, high-fat meals may decrease the absorption of glycopyrrolate when taken orally. It is recommended to take on an empty stomach, 1 hour before or 2 hours after meals for optimal absorption. |
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| Monitor maternal heart rate and blood pressure; assess fetal heart rate if prolonged use near term for anticholinergic effects. |
| Fertility Effects | No significant impact on fertility in animal studies; human data limited. |
| Clinical Pearls | Glycopyrrolate is a quaternary ammonium anticholinergic that does not cross the blood-brain barrier, thus minimizing central nervous system side effects. It is used for reducing secretions in anesthesia (e.g., to prevent bradycardia and reduce salivation) and for treating drooling in children with neurologic conditions. Onset after IV administration is 1-2 minutes; duration is about 2-4 hours. Avoid use in patients with myasthenia gravis, glaucoma, or obstructive uropathy. May cause heat prostration in hot environments due to decreased sweating. |
| Patient Advice | Avoid driving or operating machinery until you know how this medication affects you, as it may cause blurred vision or dizziness. · Drink plenty of fluids unless otherwise instructed, but avoid excessive alcohol consumption as it may increase drowsiness. · Use caution in hot weather; this medication reduces sweating and can increase the risk of heat stroke. · Contact your doctor if you experience difficulty urinating, rapid or irregular heartbeat, or eye pain. · Take exactly as prescribed; do not crush or chew extended-release tablets. |