Trial Information

Garlic Metabolism and Cytochrome P450 Modulation

Garlic supplements, which are often used to lower cholesterol and prevent cancer, are one of
the most commonly used herbal products in the United States.

However, little is known about the way garlic supplements may interact with prescription
medications when used simultaneously. This study will investigate four commonly used garlic
supplements: garlic powder with a low content of allicin (a compound with antibacterial
properties), garlic powder with a high allicin content, garlic oil, and aged garlic. The
effects of these 4 garlic products on the drug-metabolizing enzyme cytochrome P450 (CYP) and
a drug transporter, P-glycoprotein (Pgp) will be examined.

Participants will be randomly assigned to receive one of the four garlic supplements for 4
weeks. Drug probes of CYP and Pgp will be used to assess the in vivo activities of the
substances. On the first day of garlic ingestion, blood collection will occur immediately
after participants ingest their garlic supplement and 3, 4, and 6 hours after ingestion.
Urine collection will occur immediately after participants' first garlic ingestion and 12,
15, and 72 hours after ingestion. Blood and urine collection will determine the
concentration of the drug probes in the body, which will indicate changes in CYP and Pgp.
Blood and urine tests will be repeated at the end of the study.