The Justice Department says the judge 's decision does not have ` ` point - of - sale . '' Key ingredient in Plan B is the synthetic drug levonorgestrel . The key ingredient in Plan B is the synthetic hormone levonorgestrel , which can prevent fertilization or , if an egg has been fertilized , prevent it from embedding in the uterus . It prevents pregnancy or , if an egg has been fertilized , prevents it from developing in the body .
The Justice Department says the judge 's decision does not have ` ` point - of - sale . '' Key ingredient in Plan B is the synthetic drug levonorgestrel . It prevents pregnancy or , if an egg has been fertilized , prevents it from developing in the body .