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

Utah System of Higher Education (USHE)

Status and phase: Completed; Phase 4

Conditions: Contraception

Treatments: Dietary Supplement: Placebo Control (Placebo Herb); Drug: Levonorgestrel; Dietary Supplement: St. John's Wort

Study type: Interventional

Funder types: Other; NIH

Identifiers

NCT00131885

13430

R21AT002297 (U.S. NIH Grant/Contract)

Details and patient eligibility

About

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

Full description

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.

Enrollment: 36 patients

Sex: Female

Ages: 18 to 30 years old

Volunteers: Accepts Healthy Volunteers

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

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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36 participants in 4 patient groups, including a placebo group

Levonorgestrel 1.5 with Placebo Herb

Placebo Comparator group

Description:

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

Treatment:

Drug: Levonorgestrel

Dietary Supplement: Placebo Control (Placebo Herb)

Levonorgestrel 1.5 with SJW 900 mg

Active Comparator group

Description:

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

Treatment:

Dietary Supplement: St. John's Wort

Drug: Levonorgestrel

Levonorgestrel 2.25 with SJW 900 mg

Active Comparator group

Description:

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

Treatment:

Dietary Supplement: St. John's Wort

Drug: Levonorgestrel

Levonorgestrel 1.5 with SJW 1500 mg

Active Comparator group

Description:

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

Treatment:

Dietary Supplement: St. John's Wort

Drug: Levonorgestrel