Which adjustment is recommended when emergency contraception levonorgestrel is taken with an enzyme-inducing anticonvulsant such as phenobarbital?

• A. Increase the dose of Levonorgestrel
• B. Decrease the dose
• C. Take with a proton pump inhibitor
• D. Avoid it completely

Answer: (A)

Enzyme induction from drugs like phenobarbital speeds up the body's metabolism of levonorgestrel, reducing its plasma levels and, in turn, its effectiveness as emergency contraception. To compensate for this faster clearance and achieve similar protection, the total dose of levonorgestrel is increased—typically to about 3 mg, such as two 1.5 mg tablets given in a single dose. This higher amount helps ensure enough levonorgestrel reaches and stays in the system despite the enzyme induction. Decreasing the dose would further lower exposure and not help; taking a proton pump inhibitor won’t counteract the accelerated metabolism; and avoiding use isn’t necessary if an effective higher dose can be given.