Glycopyrrolate
Glycopyrrolate is a synthetic quaternary ammonium **antimuscarinic agent** used primarily as a preanesthetic anticholinergic, to treat bradyarrhythmias, and to reduce hypersialism (excessive salivation). Unlike atropine, its quaternary structure prevents it from crossing the blood-brain barrier appreciably, resulting in **fewer central nervous system (CNS) side effects**. It also has a longer duration of action for controlling salivary secretions compared to atropine. > **Clinical Pearl:** Glycopyrrolate is often preferred over atropine for preanesthetic use when prolonged reduction of salivary and respiratory secretions is desired without the risk of CNS stimulation or depression.
Mecanismo: Glycopyrrolate acts as a competitive antagonist of **acetylcholine** at postganglionic **muscarinic receptors** (M1, M2, M3). **Acetylcholine** → Blocked at **Muscarinic Receptors** → Decreased parasympathetic tone. This blockade leads to: - **Heart:** Vagolytic effect → Increased heart rate (tachycardia). - **Secretions:** Antisialagogue effect → Profound reduction in salivary, tracheobronchial, and pharyngeal secretions. - **GI/Urinary:** Decreased smooth muscle motility and tone. - **Eye:** Mydriasis (pupil dilation) and cycloplegia.
Dosificación por especie
- As an adjunct to anesthesia · 0.011 mg/kg · IM · For maximum effect give 15 minutes prior to anesthetic administration
- For bradyarrhythmias · 0.005-0.01 mg/kg IV or IM, 0.01-0.02 mg/kg SC · IV, IM, SC
- Associated with anesthesia · 0.005-0.01 mg/kg · IV
- As a premed · 0.01 mg/kg · SC or IM
- As a premed · 0.01-0.02 mg/kg · IM or IV
- For treatment of bradyarrhythmias · 0.005-0.01 mg/kg (5-10 micrograms/kg) · IV · Note: ARCI UCGFS Class 3 Drug
- As a bronchodilator · 2-3 mg · IM · two to three times daily · Dose for a 450 kg animal
- To control muscarinic adverse effects associated with imidocarb therapy · 0.0025 mg/kg · IV
- For prevention of bradycardia and to decrease airway and salivary secretions (Rabbits) · 0.01-0.1 mg/kg IM, SC; 0.01 mg/kg IV · IM, SC, IV
- As adjunct to anesthesia (Rabbits) · 0.01-0.02 mg/kg · SC · as needed
Vías de administración
Contraindicaciones
- Narrow angle glaucoma
- Tachycardias
- Gastrointestinal ileus
- Urinary obstruction
- Hypersensitivity to the drug
- Pregnancy (per some manufacturer labels)
Efectos adversos
- Dry secretions (xerostomia)
- Initial bradycardia followed by tachycardia
- Decreased gastrointestinal motility (risk of ileus)
- Decreased urinary tract motility
- Mydriasis and cycloplegia
Interacciones farmacológicas
- Amantadine · May enhance the activity or toxicity of glycopyrrolate.
- Antihistamines (e.g., diphenhydramine) · May enhance anticholinergic activity or toxicity.
- Meperidine · May enhance anticholinergic activity or toxicity.
- Phenothiazines · May enhance anticholinergic activity or toxicity.
- Tricyclic Antidepressants (e.g., amitriptyline, clomipramine) · May enhance anticholinergic activity or toxicity.
- Amitraz · May aggravate signs seen with amitraz toxicity, leading to hypertension and further inhibition of peristalsis.
- Antacids · May decrease PO absorption; give oral glycopyrrolate at least 1 hour prior to oral antacids.
- Corticosteroids (long-term use) · May increase intraocular pressure when used concurrently.
- Digoxin (slow-dissolving) · May increase serum digoxin levels; use regular digoxin tablets or oral liquid.
- Ketoconazole · Increased gastric pH may decrease GI absorption; administer 2 hours after ketoconazole.
- Metoclopramide · Glycopyrrolate may antagonize the prokinetic actions of metoclopramide.
Monitorización
- Heart rate and rhythm
- Respiratory rate and effort
- Gastrointestinal motility (auscultation for bowel sounds)
- Salivary and respiratory secretions
Sobredosis
In dogs, the LD50 is reported to be 25 mg/kg IV. In cats, the LD50 after IM injection is 283 mg/kg. Because of its quaternary structure, **minimal CNS effects** would be expected after an overdose compared to atropine. Overdose may present with severe anticholinergic signs (extreme tachycardia, mydriasis, dry mucous membranes, ileus). Treatment is generally supportive.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.