A total of 193 drugs (701 brand and generic names) are known to interact with Plan B (levonorgestrel). 13 major drug interactions (37 brand and generic names)
157 moderate drug interactions (603 brand and generic names)
23 minor drug interactions (61 brand and generic names)
http://www.drugs.com/drug-interactions/levonorgestrel,plan-b.html
As opposed to aspirin.
A total of 470 drugs (1954 brand and generic names) are known to interact with aspirin.
76 major drug interactions (326 brand and generic names)
321 moderate drug interactions (1310 brand and generic names)
73 minor drug interactions (318 brand and generic names)
http://www.drugs.com/drug-interactions/aspirin.html