A guy starts working as an ambulance driver, and is paired to an experienced ambulance driver, who starts corrupting him and getting him into drugs.
There is a very distinctive scene at the end of the movie - the senior ambulance driver is shot through the palm of his hand - he was trying to buy/sell drugs, but was somehow cheating - either he was selling aspirin saying it's drugs, or he was buying but driving off before giving any money.
There is another scene - they are at a drug addicts' den, and one of the other drug addicts suddenly suffers from an overdose. The junior ambulance driver wants to take him into the ambulance they've parked nearby, but the senior ambulance driver dissuades him, saying they would be fired, so they escape instead.
I don't really remember much more than that.
I watched the movie on TV, 10-15 years ago. I think it was a low-budget movie.