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Garlic Metabolism and Cytochrome P450 Modulation

Phase 4
18 Years
45 Years
Not Enrolling

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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.

Inclusion Criteria:

- Body mass index (BMI) between 20 and 32

- Able to read and understand English


Exclusion Criteria:

- Current use of herbal medicines other than oral contraceptives

- History of cardiopulmonary, liver, renal or endocrine disease

- Allergy or sensitivity to any of the drugs that will be used in the probe cocktails
or the garlic supplements

- Daily consumption of vegetables with a high allium content, including garlic,
shallots, leeks, and chives

- Pregnancy or breastfeeding

Type of Study:


Study Design:

Observational Model: Case-Only, Time Perspective: Prospective

Outcome Measure:

Blood plasma and urine samples

Outcome Time Frame:

3 months

Safety Issue:


Principal Investigator

Danny D. Shen, PhD

Investigator Role:

Principal Investigator

Investigator Affiliation:

Fred Hutchinson Cancer Research Center


United States: Federal Government

Study ID:




Start Date:

July 2005

Completion Date:

March 2009

Related Keywords:

  • Healthy
  • Drug Interactions
  • Pharmacokinetics
  • Garlic
  • Complementary Therapies
  • Complementary and Alternative Medicine



Fred Hutchinson Cancer Research Center Seattle, Washington  98109