Cocaine is a very effective vasoconstrictor on contact. Years ago when I was moonlighting in the Emergency Room (before the ER Specialty was established) a dilute solution of cocaine was routinely used to stop a small localized area of bleeding on the nasal septum. read more
The cocaine itself can cause nose bleeds from direct irritation of the nasal mucosa. In addition, it is often cut with rat poison. Rat poison is a blood thinner; the idea is to open up the vessels so more of the drug gets in. A byproduct of this is that your nose will bleed more. read more
To answer you question--yes, cocaine use can cause bloody noses. The mechanism of this is that when one snorts cocaine they can directly irritate the nasal mucosa (inner part of nose) causing it to bleed. The inner part of the nose has a lot of blood supply and thin skin so the nosebleed can be profuse. read more