Answer
Yes, St John's wort can reduce the contraceptive effectiveness of Logynon (ethinylestradiol + levonorgestrel) by inducing enzymes that increase sex-hormone clearance, potentially causing breakthrough bleeding or contraceptive failure.
Sources for this answer
- LogynonBayer plc · emc · SmPC §4.5 Interaction with other medicinal products · Version 21Document updated
Sources checked