Here’s a great book on this topic. It starts with the Gary Webb episode, but stretches back to include things like partnering with Afghan Opium traffickers or supporting the Sicilian mafia to facilitate the invasion of Italy during WW2, etc.
Whiteout: The CIA, Drugs and the Press: https://www.amazon.com/Whiteout-Drugs-Press-Alexander-Cockburn/dp/1859842585/ref=nodl_
Read Whiteout, the shit goes deeper and further back than you think.
I seem to remember that this was a good book: Whiteout: The CIA, Drugs and the Press by Alexander Cockburn https://www.amazon.com/dp/1859842585/ref=cm_sw_r_tw_dp_U_x_y-6cBb7G9GPYD