Paregoric
Paregoric is an opiate-based gastrointestinal motility modifier occasionally used for the symptomatic treatment of diarrhea in veterinary patients. **Key Clinical Points:** * **Composition:** Contains 2 mg of anhydrous morphine equivalent per 5 mL, along with anise oil, glycerin, benzoic acid, camphor, and alcohol. * **Regulatory Status:** It is a Schedule III (C-III) controlled substance. * **Critical Warning:** Do **NOT** confuse paregoric with opium tincture (tincture of opium). Opium tincture contains 50 mg of anhydrous morphine equivalent per 5 mL, making it **25 times more potent** than paregoric. Fatal overdoses can occur if these are interchanged. * **Species Considerations:** Its use in cats is highly controversial due to the risk of paradoxical CNS excitation. In horses and other animals with potentially infectious diarrhea, opiates can delay the clearance of pathogens and worsen the clinical picture.
Mechanism: Paregoric exerts its antidiarrheal effects primarily through the action of morphine on **mu-opioid receptors** in the gastrointestinal tract. * **Motility Inhibition:** Binding to enteric opioid receptors decreases the release of acetylcholine → inhibits excessive GI propulsion and peristalsis, increasing intestinal transit time. * **Secretion Reduction:** Decreases intestinal secretion induced by cholera toxin, prostaglandin E2, and calcium-mediated (non-cyclic AMP/GMP mediated) diarrheas. * **Absorption:** Prolonged transit time allows for enhanced mucosal absorption of water and electrolytes, solidifying the stool.
Dosing by species
- Maldigestion, malabsorption, anti-diarrheal · 0.05-0.06 mg/kg PO two to three times daily · PO · BID to TID · Use is controversial; this species may react with excitatory behavior.
- Antidiarrheal · 15-30 mL PO · PO · Dose for calves.
- Antidiarrheal · 15-30 mL PO (Foals); 15-60 mL PO (Adults) · PO · May have a detrimental effect in acute/bacterial diarrhea by delaying microbe clearance.
- Acute colitis · 0.06 mg/kg PO three times daily · PO · TID
- Maldigestion; malabsorption; antidiarrheal · 0.05-0.06 mg/kg PO two to three times daily · PO · BID to TID
- Antidiarrheal · 0.05-0.06 mg/kg PO q12h · PO · q12h
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Known hypersensitivity to narcotic analgesics
- Patients receiving monoamine oxidase inhibitors (MAOIs)
- Diarrhea caused by toxic ingestion (until the toxin is eliminated from the GI tract)
Adverse effects
- Dogs: Constipation, bloat, sedation, paralytic ileus, toxic megacolon, pancreatitis, CNS effects
- Cats: Excitatory behavior (controversial use)
- Horses: Delayed clearance of GI microbes, prolonged febrile state
Drug interactions
- CNS Depressants (anesthetics, antihistamines, phenothiazines, barbiturates, tranquilizers, alcohol) · May cause increased CNS or respiratory depression when used concurrently.
- Monoamine Oxidase Inhibitors (MAOIs, e.g., amitraz, selegiline) · Contraindicated. Opiates should not be used for at least 14 days after receiving MAOIs due to the risk of severe, potentially fatal reactions.
Monitoring
- Clinical efficacy (resolution of diarrhea)
- Fluid and electrolyte status (especially in severe diarrhea)
- CNS effects (sedation in dogs, excitation in cats), particularly if using high dosages
Overdose
Acute overdosage of opiate antidiarrheals can result in severe **CNS, cardiovascular, gastrointestinal, or respiratory toxicity**. * Because opiates significantly reduce GI motility, absorption of the drug from the GI tract may be delayed and prolonged, leading to a sustained toxic effect. * **Treatment:** Naloxone is the specific reversal agent and may be necessary to reverse opiate-induced respiratory depression and CNS effects. Supportive care is essential.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.