Cartels could be able to lace drugs to varying degrees, laced drugs increase OD risk by a percentage that is controlled by the cartel. Then sell these in the market to unwitting buyers for a profit.

Example scenario: cartel has say 100 cocaine. They choose to lace this drug at 10%. They receive 110 laced cocaine. Each of these cocaine has an OD risk that is a percent higher than normal cocaine. 

That would be a cool added perk that could be purchased with cartel respect. I wonder the code it would require to follow the laced drugs from user to user until its actually consumed. Above my pay grade....