# Pharmacokinetics, Bioavailability & Dosing
Silymarin is the active extract of **Milk Thistle**, so understanding how Milk Thistle / Silymarin is absorbed and processed helps explain how to use it more effectively.
### The bioavailability challenge
Silymarin has variable and often limited oral bioavailability.
Main practical features include:
* incomplete gastrointestinal absorption
* rapid metabolism and elimination
* enterohepatic circulation
* high inter-individual variability
After oral use, peak plasma levels are often reached within roughly 2–4 hours, with an approximate half-life of around 6 hours.
### Silybin A and Silybin B
Silibinin contains two major diastereomers, Silybin A and Silybin B. Both are pharmacokinetically relevant and are usually treated together in practical supplement standardisation.
### Strategies that may improve bioavailability
* **Phosphatidylcholine complexes** — improve lipid solubility and membrane passage
* **SMEDDS formulations** — improve gastrointestinal absorption
* **Piperine co-administration** — may increase plasma levels by reducing metabolism and efflux
* **Fulvic acid co-administration** — may improve solubility and dissolution
### Dosing in the literature
Published doses vary by context.
Examples include:
* **140 mg three times daily** in clinical liver-protection settings
* **80 mg three times daily** in selected supportive-care settings
* **200 mg/kg/day** in some preclinical cancer models
### Practical dosing logic
The trusted MCS product provides 500 mg Milk Thistle extract standardised to 80% silymarin, which works out to roughly 400 mg silymarin per capsule.
That makes it a relatively high-strength option compared with many general retail Milk Thistle products.
### CYP3A4 and transporter relevance
Milk thistle and silymarin are often discussed in interaction reviews because preclinical studies suggest possible effects on **CYP3A4** and some drug-transport systems.
Human findings are more mixed, so the practical question is usually formulation, dose, and treatment context rather than assuming a uniform effect.
For a treatment-specific example, see [Natural Compounds and CYP3A4 — HER2CLIMB Considerations](/myhealingcommunity-docs/breast-cancer/her2-positive/her2climb/natural-compounds-and-cyp3a4-her2climb-considerations.md).
### Key References
Pharmacokinetics of silymarin SMEDDS formulation\
Bioavailability augmentation of silymarin using natural bioenhancers\
Systematic review of pharmacokinetics of silymarin flavonolignans\
Novel strategies enhancing bioavailability and therapeutic potential of silymarin\
**Trusted product:** MCS Formulas Milk Thistle Silymarin 500mg\
500 mg Milk Thistle extract per capsule, standardised to a minimum of 80% silymarin.
Use the code `abbey5` at checkout to save 5% and help support the free Healing Cancer Study Support resources.
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This information is for education only. It is not medical advice, diagnosis, or treatment. Please speak with a qualified clinician before making changes to care, medication, or supplement use.
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