Im currently on nexplonon, an arm implant. will evening primrose oil have any affect on interfering with the contraception?

No worries: Vitamins, over-the-counter supplements, herbal teas, lotions, creams, oils, etc., should not have any noticeable effect on a woman's contraceptive implant. If a woman with an implant is getting symptoms that might be due to an early pregnancy, and she gets worried, she can do a home urine pregnancy test. Tests are very accurate by 3 weeks after sex.