...leading to eventual overdose. Exactly.
While using [Cocaine+Heroin] 'speedballs' about 345 days out of the 365 days in a year, I would notice that I could inject up to 3 grams of very, very high grade tar and 3 grams of Cocaine of the same quality within a 24 hour period (honest to god). The compulsive feeling of the need to re-dose from the Cocaine along with the feeling of the need to add the Heroin to "take the edge off" would lead to constant re-dosing, in absurd amounts.
However, on those [around] 20 days throughout that year that I did not use Cocaine, I would get by on under a gram of Heroin in a day, no problem. The only issue was that since 98% of my veins (aside from my neck, femoral and penis, which I refused to use, although I did tie them off a few times whilst sick and not able to find a vein. very, very surprisingly, logic+safety came into play and i never used them.) were collapsed from the chronic use of tar and the constricting properties of the Cocaine over the long periods of use, I would almost always have my shots 'leak'. Meaning that when I would find a vein, it was either so damaged that my shots would leak out into the areas surrounding it, or I would miss completely. On many occasions, this caused me to tolerate being sick for extended periods of time until I could secure Cocaine to add to the tar (for numbing effects), because the tar on it's own would burn *severely* without the Cocaine in it, especially when I was injecting in more painful areas like my feet, toes, hands, fingers.
So ultimately, there are many dangerous factors that come in to play when combining stimulants with depressants (primarily intravenous use of Opiates/oids with Stimulants). The main two, in my opinion, being: a) compulsion to re-dose (from the stimulant) and b) urge to take more of the depressant to "take the edge off". And the wheel just turns and turns...
