When to add a cathartic
Cathartics increase the speed and transit time of material in the GI tract, thus promoting fecal excretion of the toxin. More
importantly, cathartics decrease the time available for systemic toxin absorption in the GI tract.
Cathartics typically given to animals are osmotic cathartics: saccharide (e.g. sorbitol) or saline (e.g. sodium sulfate, magnesium citrate, magnesium sulfate) cathartics.1 Sorbitol, which has a sweet taste, is the most commonly given cathartic. Mineral oil is no longer recommended as a cathartic
because of the high risk of secondary aspiration.1
Evidence for efficacy
No published clinical studies have investigated the use of a cathartic (with or without activated charcoal) in reducing the
bioavailability of drugs or in improving the clinical outcome of poisoned human patients.2 Unfortunately, there is also limited literature evaluating cathartic administration in veterinary medicine, and there are
no prospective studies evaluating its use in poisoned patients.
Although cathartics are no longer recommended for use in people,2 in veterinary medicine, one dose of a cathartic with the first dose of activated charcoal is likely appropriate as it may
help accelerate GI transit time, lessening the potential of toxicant and activated charcoal desorption.
Many sources of activated charcoal already have sorbitol mixed in and generally can be used as directed on the label (e.g. ToxiBan with sorbitol—Vet-a-Mix; 10 to 20 ml/kg orally). Multidose activated charcoal should not contain cathartics.1,3 If a combination product is not available for the first dose, sorbitol is available as a lone ingredient and can either
be mixed with the activated charcoal or given separately immediately after activated charcoal administration or within 60
minutes of toxicant ingestion (70% solution—1 to 2 ml/kg orally).1,3
Adverse effects and contraindications
Adverse side effects of cathartic administration include vomiting, abdominal cramping or pain, diarrhea, dehydration, secondary
hypernatremia, and possible hypotension. Serious adverse effects can occur if multiple doses of cathartics are given, in particular
dehydration and electrolyte abnormalities, including hypernatremia and hypermagnesemia when using a sodium- or magnesium-containing
Administering cathartics in patients that are dehydrated or fasted, have severe vomiting and diarrhea, or have preexisting
renal disease is contraindicated.3
Most of the contraindications for cathartic administration are similar to those for activated charcoal administration.1,3
1. Lee JA. Decontamination and detoxification of the poisoned patient. In: Osweiler GD, Hovda LR, Brutlag AG, et al., eds. Five-minute veterinary consult clinical companion: small animal toxicology. 1st ed. Ames, Iowa: Wiley-Blackwell, 2011;5-19.
2. American Academy of Clinical Toxicology and European Association of Poisons Centres and Clinical Toxicologists. Position paper:
cathartics. Clin Tox 2004;42(3):243-253.
3. Lee JA. Complications and controversies of decontamination: activated charcoal—to use or not to use, in Proceedings. Am Coll Vet Intern Med Conf, 2010.