Heroin has very effective abilities in both the euphoric and analgesic areas. This essentially means that it creates an intense feeling of well being and relief from stresses and it relieves physical pains. Many users will feel an increase in self-confidence, an empathy with people around them, and some users report increased creativity. Larger doses will create a dreamlike state, with visual distortions, which could be described as hallucinations. In a pure form heroin does not take a great toll on the body, but there are some side-effects.
Constipation is a fairly uncomfortable one.
Nausea can effect many users. Response time is certainly slowed, making driving dangerous. Heroin slows down breathing, and can stop it altogether. Most heroin overdoses occur when heroin is combined with other drugs with a depressant effect, particularly alcohol and sleeping pills like Valium or Normison. While overdoses caused by a single high IV dose of pure heroin may cause immediate death, many overdose victims do not fall into an immediate coma as is often the portrayal of OD in popular culture.