Exactly! Cocaine is extremely habit-forming. It is potentially dangerous when indulged in to excess. If rats or monkeys are hooked up to an intravenous source of heroin, they will happily self-administer the drug indefinitely; but they still find time to sleep and eat.
If rats or monkeys can freely self-administer cocaine, however, they will do virtually nothing else. Captive animals continue to press their drug-delivery lever for as long as they are physically capable of doing so. Their fate is similar to an intracranially self-stimulating laboratory rodent. Within weeks, if not days, they will lose a substantial portion of their body weight - up to 40%. Within a month, they will be dead.
Cocaine and amphetamines concentrate in the central link of the reward circuit (the ventral tegmental area and the nucleus accumbens). These areas contain especially high concentrations of dopaminergic synapses, which are the preferred target of these drugs.
Cocaine's effects on other structures such as the caudate nucleus may explain certain secondary effects of this drug, such as increased stereotyped behaviours (nail biting, scratching, etc.)