Cocaine powder is absorbed by the nasal mucous membrane and will then get into the blood. The level of cocaine in the blood rises slowly and then goes slowly down again. In total, the effects will last 20-30 minutes. Sometimes cocaine powder is also smoked. A small part of the cocaine gets into the blood through the lungs, which gives a short but heavy effect. Cocaine powder has a melting temperature of 197 o C. When the temperature gets higher the cocaine powder could evaporate and be smoked, but when it reaches that temperature the cocaine powder falls apart and/or burns. That is why cocaine powder can actually not be smoked. Even before it evaporates, it is no longer cocaine. So, most cocaine is lost by smoking, and only a small portion reaches the lungs. Smoking cocaine powder can cause small amounts of burned cocaine to get into the airways or the lungs. Moreover, other substances that are set free during the burning can reach the lungs and cause damage. Anyway, the lungs are well protected because the throat and airways bear the brunt of the damage. However, when the symptoms persist, please consult a doctor.
It is possible to smoke cocaine in the form of crack. Crack is made by heating cocaine and basicity substances (p.e. ammonia or sal ammoniac). Smoking crack makes you extremely addicted. Already after the first use, you feel a craving for the next dose of crack. Furthermore crack is very harmful to your health and leads to severe psychological problems.
For infrequent use, the cocaine is usually not detectable in the blood after 2-3 days.