S-Adenosyl-Methionine (SAMe)
**S-Adenosyl-Methionine (SAMe)** is a naturally occurring endogenous molecule and a highly utilized veterinary nutraceutical, primarily serving as a **hepatoprotectant**. Key clinical applications include: * **Liver Disease**: Used as an adjunctive treatment for chronic hepatitis, hepatic lipidosis, cholangiohepatitis, and feline triad disease. * **Toxicity Management**: Crucial in the treatment of acute hepatotoxin-induced liver injury, such as **acetaminophen** or **xylitol** toxicity, by replenishing depleted glutathione stores. * **Additional Uses**: May benefit patients with osteoarthritis, age-related cognitive dysfunction (canine cognitive dysfunction syndrome), and those on long-term hepatotoxic medications (e.g., phenobarbital, lomustine). > **Clinical Pearl**: Because SAMe is highly reactive and unstable, commercial formulations use various salt forms (e.g., tosylate, butanedisulfonate) to improve stability. Bioavailability varies significantly between products, so choosing a reputable, veterinary-specific brand is highly recommended.
Mechanism: SAMe is synthesized from the amino acid methionine and ATP via the enzyme **SAMe synthetase**. In liver compromise, this enzyme's activity is a rate-limiting step, leading to systemic SAMe deficiency. Exogenous SAMe bypasses this block and participates in three major biochemical pathways: * **Transsulfuration** โ Generates sulfur-containing compounds โ Precursor to **Glutathione (GSH)**. Glutathione is the liver's master antioxidant, essential for ROS scavenging and cellular detoxification. Exogenous SAMe prevents GSH depletion. * **Transmethylation** โ Serves as a methyl donor โ Essential for phospholipid synthesis (e.g., phosphatidylcholine) โ Maintains cell membrane structure, fluidity, and function. * **Aminopropylation** โ Donates aminopropyl groups โ Source of polyamines โ Promotes anti-inflammatory effects, protein/DNA synthesis, and **hepatocyte replication/regeneration**. Additionally, SAMe inhibits hepatocyte apoptosis secondary to alcohol or bile acid accumulation.
Dosing by species
- General dosing / Liver support ยท 18 mg/kg (or based on weight: <5.5 kg: 90 mg; 5.5-11 kg: 180-225 mg) ยท PO ยท q24h ยท Give on an empty stomach, at least one hour before feeding.
- Liver Disease (necro-inflammatory/cholestatic, feline hepatic lipidosis) ยท 20 mg/kg ยท PO ยท q24h ยท Give on an empty stomach; use a proven bioavailable product.
- Liver disease, cognitive dysfunction, improve bile flow ยท 100 mg/cat or 20 mg/kg ยท PO ยท q24h ยท Long-term as needed ยท Administer on an empty stomach at least 1 hour before food. Tablets should be given whole.
- General dosing / Liver support ยท 18 mg/kg (or based on weight: <5.5 kg: 90 mg; 5.5-11 kg: 180-225 mg; 11-16 kg: 225 mg; 16-29.5 kg: 450 mg; 29.5-41 kg: 675 mg; >41 kg: 900 mg) ยท PO ยท q24h (may divide q12h if giving >1 tablet) ยท Give on an empty stomach, at least one hour before feeding.
- Liver Disease (necro-inflammatory/cholestatic, vacuolar hepatopathy) ยท 20 mg/kg ยท PO ยท q24h ยท Give on an empty stomach; use a proven bioavailable product.
- Liver disease, cognitive dysfunction, adjunctive therapy ยท At least 100 mg for every 10 kg or 20 mg/kg ยท PO ยท q24h ยท Long-term as needed ยท Administer on an empty stomach at least 1 hour before food. Tablets should be given whole.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- No absolute contraindications
- Use with caution in pregnant animals (safety not definitively proven)
- No absolute contraindications documented
- Use with caution during pregnancy (safety not established)
Adverse effects
- Immediate post-dose vomiting
- Anorexia
- Anxiety
- Nausea (reported in humans)
- Diarrhea (reported in humans)
- Flatulence (reported in humans)
- Nausea
- Vomiting
- Diarrhoea
- Paradoxical anxiety
- Dry mouth (reported in humans)
- Headache (reported in humans)
- Sweating (reported in humans)
- Dizziness (reported in humans)
Drug interactions
- Tramadol ยท Theoretical risk of additive serotonergic effects (serotonin syndrome) ยท major
- Meperidine ยท Theoretical risk of additive serotonergic effects ยท major
- Dextromethorphan ยท Theoretical risk of additive serotonergic effects
- Pentazocine ยท Theoretical risk of additive serotonergic effects ยท major
- Monoamine oxidase inhibitors (MAOIs) (e.g., selegiline) ยท Theoretical risk of additive serotonergic effects
- Selective serotonin reuptake inhibitors (SSRIs) (e.g., fluoxetine) ยท Theoretical risk of additive serotonergic effects
- Tricyclic antidepressants (TCAs) (e.g., amitriptyline, clomipramine) ยท Theoretical risk of additive serotonergic effects
- Selegiline ยท Additive serotonergic effects; potential for serotonin syndrome ยท major
- Fluoxetine ยท Additive serotonergic effects; potential for serotonin syndrome ยท major
- Clomipramine ยท Additive serotonergic effects; potential for serotonin syndrome ยท major
- Amitriptyline ยท Additive serotonergic effects; potential for serotonin syndrome ยท major
- Paracetamol ยท SAMe may increase the clearance of drugs undergoing hepatic glucuronidation ยท moderate
Monitoring
- Clinical signs (appetite, activity, attitude)
- Liver enzymes (ALT, AST, ALP, GGT)
- Bilirubin
- Bile acids
- Liver biopsies (if indicated)
- Hepatic and erythrocyte glutathione levels (Note: may require 1-4 months before changes in lab values are noted)
- Liver enzyme panel (ALT, AST, ALP, GGT)
- Total bilirubin and bile acids
- Clinical signs of cognitive improvement or behavioral changes
- Signs of serotonin syndrome (agitation, tremors, hyperthermia) if used concurrently with serotonergic drugs
Overdose
SAMe appears to be quite safe. The LD50 in rodents exceeds 4.65 grams/kg. Toxicity studies in dogs and cats at usual prescribed dosages demonstrated no deleterious effects. In the event of a massive overdose, mild gastrointestinal effects (nausea, vomiting, diarrhea) may be observed, but it is highly unlikely to require specific medical treatment beyond supportive care.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.