DRUGS OR HERBAL PRODUCTS THAT INDUCE SUCH ENZYMES MAY DECREASE THE PLASMA CONCENTRATIONS OF CONTRACEPTIVE HORMONES, AND MAY DECREASE THE EFFECTIVENESS OF HORMONAL CONTRACEPTIVES OR INCREASE BREAKTHROUGH BLEEDING. SOME DRUGS OR HERBAL PRODUCTS THAT MAY DECREASE THE EFFECTIVENESS OF HORMONAL CONTRACEPTIVES INCLUDE:
BARBITURATES, BOSENTAN, CARBAMAZEPINE, FELBAMATE, GRISEOFULVIN, OXCARBAZEPINE, PHENYTOIN, RIFAMPIN, ST. JOHN'S WORT, TOPIRAMATE.
HIV PROTEASE INHIBITORS: SIGNIFICANT CHANGES (INCREASE OR DECREASE) IN THE PLASMA LEVELS OF THE ESTROGEN AND PROGESTIN HAVE BEEN NOTED IN SOME CASES OF CO-ADMINISTRATION OF HIV PROTEASE INHIBITORS.
INCREASED PLASMA CONCENTRATIONS OF CYCLOSPORINE, PREDNISOLONE, AND THEOPHYLLINE HAVE BEEN REPORTED WITH CONCOMITANT ADMINISTRATION OF ORAL CONTRACEPTIVES. IN ADDITION, ORAL CONTRACEPTIVES MAY INDUCE THE CONJUGATION OF OTHER COMPOUNDS. DECREASED PLASMA CONCENTRATIONS OF ACETAMINOPHEN AND INCREASED CLEARANCE OF TEMAZEPAM, SALICYLIC ACID, MORPHINE AND CLOFIBRIC ACID HAVE BEEN NOTED.
COMBINED HORMONAL CONTRACEPTIVES HAVE BEEN SHOWN TO SIGNIFICANTLY DECREASE PLASMA CONCENTRATIONS OF LAMOTRIGINE WHEN CO-ADMINISTERED LIKELY DUE TO INDUCTION OF LAMOTRIGINE GLUCURONIDATION. THIS MAY REDUCE SEIZURE CONTROL; THEREFORE, DOSAGE ADJUSTMENTS OF LAMOTRIGINE MAY BE NECESSARY.