I have the Implanon contraceptive implant, and have it for less than a year (had one for the three years before that), and I have recently taken a herbal tonic containing st johns wort. I have not had sexual intercourse in a while, and am not planning to anytime soon, but I was would like to know if the one off dosage (i think it was a reasonably high dosage) will affect the overall efficiency of the inplanon?