Cathartic and Laxative Drugs



Castor oil

Dogs: 5–25 mL, PO, q 12–24 h or to effect


Dogs: 5–20 mg, PO, q 12–24 h

Cats: 2.5–5 mg, PO, q 12–24 h

Magnesium sulfate (Epsom salts)

Dogs: 5–25 g, PO, as needed

Cats: 2–5 g, PO, as needed

Horses: 30–100 g, PO, repeated in 8–12 h if needed

Magnesium hydroxide (milk of magnesia)

Dogs: 5–10 mL, PO, as needed

Cats: 2–6 mL, PO, as needed

Horses: 1–4 L, PO, q 24 h


Dogs: 0.25–0.5 mL/kg, PO, q 6–8 h

0.6–1.2 g of lactulose crystals, PO in food, q 6–8 h

Docusate sodium, docusate calcium, docusate potassium

Dogs, cats: 2 mg/kg, PO, q 24 h

Horses: 10–20 mg/kg in 2 L of water

Polyethylene glycol 3350

Cats: 0.3–0.6 g, PO in food, q 12 h