Effects of St. John's Wort on the Oral Contraceptive Hormone Levonorgestrel

Study Results

Results available

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Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

PHASE4

Total Enrollment

36 participants

Study Classification

INTERVENTIONAL

Study Start Date

2005-08-31

Study Completion Date

2008-05-31

Brief Summary

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This study will determine the effects of St. John's wort, a common herbal remedy, on metabolism of the female contraceptive hormone levonorgestrel.

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Detailed Description

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In the last decade, St. John's wort has become one of the most commonly used botanicals. Levonorgestrel is a form of progesterone, a female hormone involved in conception. It can be given as both a pill and an injection and is used for contraception and for the treatment of endometriosis. However, evidence suggests that St. John's wort may reduce the effectiveness of the contraceptive hormone levonorgestrel. This study will determine whether interactions between St. John's wort and levonorgestrel reduce the effectiveness of the hormone. This study will also determine whether a higher dose of levonorgestrel will override the effects of St. John's wort.

All participants will receive a single dose of levonorgestrel between Days 9 and 12 of their first menstrual cycle after entering this study. Blood and urine collection will occur immediately after the levonorgestrel is given and every week until participants' next menstrual cycle to determine the levels of reproductive hormones in participants' bodies.

At the beginning of participants' next menstrual cycle, they will be randomly assigned to one of four groups and receive either St. John's wort or placebo for 6 weeks. Group 1 will receive a placebo; Groups 2 and 3 will receive a standard dose of St. John's wort (900 mg per day); and Group 4 will receive an increased dose of St. John's wort (1500 mg per day). After 6 weeks, Groups 1, 2, and 4 will receive 150 mcg levonorgestrel; and Group 3 will receive 225 mcg levonorgestrel. Blood and urine collection will occur immediately after levonorgestrel is given and every week until participants' next menstrual cycle.

Conditions

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Contraception

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

PARALLEL

Primary Study Purpose

TREATMENT

Blinding Strategy

SINGLE

Participants

Study Groups

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Levonorgestrel 1.5 with Placebo Herb

This group had baseline pharmacokinetic studies after an oral dose of levonorgestrel (LNG) 1.5 mg, then took a placebo herb daily for 4-6 weeks, during which time pharmacokinetic studies were repeated after an oral dose of LNG 1.5 mg

Group Type PLACEBO_COMPARATOR

Placebo Control (Placebo Herb)

Intervention Type DIETARY_SUPPLEMENT

Placebo herb three times daily (ground cellulose) for 4-6 weeks

Levonorgestrel

Intervention Type DRUG

Levonorgestrel in a single oral dose

Levonorgestrel 1.5 with SJW 900 mg

This group had baseline pharmacokinetic studies after an oral dose of levonorgestrel (LNG) 1.5 mg, then took St. John's Wort (SJW) 900 mg a Day orally for 4-6 weeks, during which time pharmacokinetic studies were repeated after an oral dose of LNG 1.5 mg

Group Type ACTIVE_COMPARATOR

St. John's Wort

Intervention Type DIETARY_SUPPLEMENT

St. John's Wort (Hypericum perforatum) orally or 4-6 weeks

Levonorgestrel

Intervention Type DRUG

Levonorgestrel in a single oral dose

Levonorgestrel 2.25 with SJW 900 mg

This group had baseline pharmacokinetic studies after an oral dose of levonorgestrel (LNG) 1.5 mg, then took a St. Johns's Wort 300 mg capsules three times daily for 4-6 weeks, during which time pharmacokinetic studies were repeated after an oral dose of LNG 2.25 mg

Group Type ACTIVE_COMPARATOR

St. John's Wort

Intervention Type DIETARY_SUPPLEMENT

St. John's Wort (Hypericum perforatum) orally or 4-6 weeks

Levonorgestrel

Intervention Type DRUG

Levonorgestrel in a single oral dose

Levonorgestrel 1.5 with SJW 1500 mg

This group had baseline pharmacokinetic studies after an oral dose of levonorgestrel (LNG) 1.5 mg, then took a St. Johns's Wort 300 mg capsules five times daily for 4-6 weeks, during which time pharmacokinetic studies were repeated after an oral dose of LNG 1.5 mg

Group Type ACTIVE_COMPARATOR

St. John's Wort

Intervention Type DIETARY_SUPPLEMENT

St. John's Wort (Hypericum perforatum) orally or 4-6 weeks

Levonorgestrel

Intervention Type DRUG

Levonorgestrel in a single oral dose

Interventions

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Placebo Control (Placebo Herb)

Placebo herb three times daily (ground cellulose) for 4-6 weeks

Intervention Type DIETARY_SUPPLEMENT

St. John's Wort

St. John's Wort (Hypericum perforatum) orally or 4-6 weeks

Intervention Type DIETARY_SUPPLEMENT

Levonorgestrel

Levonorgestrel in a single oral dose

Intervention Type DRUG

Eligibility Criteria

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Inclusion Criteria

* Body mass index (BMI) between 20 and 25
* Regular menstrual cycles for at least 3 months prior to study entry

Exclusion Criteria

* Current use of foods, herbs, vitamins, over-the-counter supplements, or any medications that could alter pharmacokinetics of other drugs
* Medical contraindications to the use of contraceptives

Minimum Eligible Age

18 Years

Maximum Eligible Age

30 Years

Eligible Sex

FEMALE

Accepts Healthy Volunteers

Yes