At high doses of stimulants, a characteristic psychosis is observed. Laboratory studies, when volunteers take amphetamines, cocaine, phenmethrazine (Preludin) or methylphenidates (Ritalin), confirm this. Such reactions with large doses of crack create a serious problem.
Paranoid disorder is the most common symptom of stimulatory psychosis. Another frequent symptom is an impulsive, stereotypical behavior; a person shakes, tears his hair, smokes cigarettes one by one, turns some thing in his hands. Sometimes there are hallucinations and goosebumps. Stimulatory psychosis is successfully treated with chlorpromazine (Thorazine) or other substances used in the treatment of schizophrenia.

Of course, large doses of cocaine or amphetamines are always accompanied by the risk of death from overdose. It is difficult to accurately determine the dose at which this risk begins. For cocaine, a small or moderate dose means 15-60 mg. (Usually, the “lane” contains 16–20 mg.) But there have been deaths from cocaine overdose, when people were given only 20 mg as a local anesthetic. Apparently they suffered a rare case of enzyme deficiency, which destroy cocaine in the blood and liver. These cases are exceptions, usually stimulatory psychosis or death occurs at much higher doses. In 1985, more than 500 people died from cocaine overdose in the US, but for many the compelling argument that cocaine kills were the deaths of athletes Len Bias, Don Rogers and film actor John Belushi. Stimulants can kill in different ways:
Cocaine can cause convulsions or a seizure that ends in suffocation.
Cocaine directly affects the nerve cells of the heart, which can cause a change in the rhythm of the heartbeat (arrhythmia). In severe cases, this can lead to fibrillation — a condition where the heart vibrates but does not pump blood.

Cocaine can cause a spasm of the coronary artery and the termination of blood access to the heart muscle. This leads to myocardial infarction and heart failure if the person remains alive.
Cocaine can cause a rupture of the cerebral artery due to high blood pressure, which can cause an attack. These are the most likely causes of death from cocaine overdose. Which factor causes death in a particular case is rarely established. Often the case is further complicated by the fact that other drugs are mixed with cocaine in order to bring about new sensations, and the result of such mixing is often unpredictable.