A 28-year-old female with bipolar II disorder has been taking carbamazepine 800 mg daily for mood stabilization with good therapeutic response. Her carbamazepine level is 8.2 mcg/mL. She reports to her PMHNP that she recently started a combined oral contraceptive pill containing ethinyl estradiol 30 mcg and levonorgestrel 150 mcg for birth control. She asks whether there are any concerns about this combination. Which of the following best describes the pharmacokinetic interaction the PMHNP should address?