Silymarin
Silymarin is a mixture of milk-thistle flavonolignans used as a hepatic supplement. Silybin, also called silibinin, is a major active constituent, and product design influences its oral availability. Veterinary use is mainly adjunctive in selected liver disorders or hepatotoxic exposures. Clinical evidence is less developed than experimental evidence for antioxidant effects.
Group
Hepatic nutritional supplement
Mechanism of Action
Silymarin constituents can scavenge reactive species, limit lipid peroxidation and support cellular antioxidant defenses, including glutathione-related pathways. Proposed effects on membrane stability and inflammatory signaling may reduce some forms of experimental hepatocellular injury. The relative contribution of these mechanisms after oral supplementation depends on formulation and exposure, and disease-specific clinical effects remain incompletely characterized.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hepatic support | 5–15 mg/kg | PO | Every 24 h | |
| Higher-dose hepatic support | Reference only | PO | Some sources in the clinical guidance suggest at least 30 mg/kg/day PO but do not give a defined upper endpoint; no invented range. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hepatic support | 5–15 mg/kg | PO | Every 24 h | |
| Higher-dose hepatic support | Reference only | PO | Some sources in the clinical guidance suggest at least 30 mg/kg/day PO but do not give a defined upper endpoint; no invented range. |
Indications
- Adjunctive hepatic support in selected dogs, cats or horses with liver disease, with limited controlled clinical outcome evidence.
- Adjunctive management of selected toxic or drug-associated hepatic injury within a complete treatment plan.
- Selected hepatoprotective supplementation during potentially hepatotoxic treatment, including supported SAMe–silybin combination use in dogs, with limited evidence.
Adverse effects
- No specific adverse reactions are described in the clinical guidance.
Toxicity
GI effects may occur after excess supplement ingestion; formulation and coingredients affect risk.
Monitoring and Administration
Follow liver injury markers. Products differ in purity and constituent amounts; silymarin and silybin-complex strengths are not interchangeable.
Horses: 6.5, 13 or 26 mg/kg every 12 hours for 7 days produced only minor antioxidant effects; clinically effective large-animal dosing is not established. Route is not explicit in the reported regimen.
Additional silymarin reports suggest 20-50 mg/kg/day, or fixed 50-250 mg/day; another uses 50-200 mg every 12-24 hours and feline guidance 4-8 mg/kg/day. These lines omit route and do not establish equivalence between silymarin, silybin and phosphatidylcholine complexes; retain without a normalized route or strength conversion.