What medications may cause contraceptive failure on Norplant?
Medications that affect the hepatic enzyme system should be avoided in women using Norplant because of lower blood levels of Levonorgestrel. These medications include Rifampin , Grisiofulvin and many anti-convulsants (Carbamazepine, Ethosuximide Phenobarbital, Phenytoin and Primidone). Norplant should also be avoided in epileptics because anti-epileptic drugs lower serum progestin levels secondary to increased protein binding altering Norplant’s effectiveness.
