Cocaine blocks pain sensation and stimulates the central nervous system, producing a sudden increase in heart rate, temperature, and blood pressure. In the brain, it blocks the synaptic reabsorption of certain neurotransmitters (in particular dopamine). The resultant buildup of neurotransmitters causes pleasurable sensations to be passed along the neural pathways over and over again, creating a feeling of profound well-being, self-confidence, and alertness. It is accompanied by lack of hunger. The effect lasts for 10 to 30 minutes, and the user begins to crave more immediately as the neurotransmitter supply is exhausted. This pattern has led to cocaine's being described as "neuropsychologically addicting" in recognition that traditional definitions of physical vs. psychological addiction do not neatly fit in this case. Most cocaine addicts in treatment report some control over their use for the first two to four years, giving them the illusion that addiction will not develop.
Addiction is characterized by binges (usually of 4 to 24 hours, one to seven times per week), movement to intravenous use or smoking, extreme euphoria, and disregard for anything other than the drug, including food, sleep, sex, family, and survival. The behavior is limited only by the high cost of the drug and its limited availability. Abstinence after a cocaine binge leads to crashing (anxiety, depression, suspiciousness, sleep craving) and withdrawal (absence of pleasure in all things, lack of motivation, and boredom). Many users take other drugs (alcohol, marijuana, heroin) to attenuate these effects. A dangerous combination of cocaine and heroin, known as a "speedball," is used by some. Withdrawal usually results in further use, often spurred by a conditioned cue such as a specific smell or location linked with cocaine use. If the drug is not taken again there is a gradual lessening of the craving, although conditioned cues may exert an effect years afterward. Long-term use can result in digestive disorders, weight loss, general physical deterioration, and marked deterioration of the nervous system. Most drug-related emergency room visits are cocaine-related.