Effects of St. John's Wort on the Oral Contraceptive Hormone Levonorgestrel
| Status: | Completed |
|---|---|
| Conditions: | Contraception, Contraception |
| Therapuetic Areas: | Reproductive |
| Healthy: | No |
| Age Range: | 18 - 30 |
| Updated: | 4/21/2016 |
| Start Date: | August 2005 |
| End Date: | May 2008 |
Effects of St. John's Wort on Levonorgestrel
This study will determine the effects of St. John's wort, a common herbal remedy, on
metabolism of the female contraceptive hormone levonorgestrel.
metabolism of the female contraceptive hormone levonorgestrel.
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.
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.
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
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