Final answer:
Cocaine, pure narcotics (if they are unadulterated CNS stimulants), and most amphetamines fall under the drug class called stimulants, which increase neural activity and often affect dopamine neurotransmission.
Step-by-step explanation:
Classification of Cocaine, Pure Narcotics, and Most Amphetamines
Cocaine, pure narcotics, and most amphetamines can be classified into the drug class of stimulants. This class includes substances that increase neural activity and are often known to affect dopamine neurotransmission resulting in effects such as euphoria, increased alertness, and heightened energy levels. For instance, cocaine is a tropane alkaloid that acts as an agonist of the dopamine system, impeding the reuptake of dopamine and causing more dopamine to be released into the synaptic cleft. Similarly, amphetamines, which include drugs like methamphetamine and MDMA (ecstasy), function by blocking the reuptake of dopamine and stimulating its release, affecting the brain's centers for reward and craving, leading to their high potential for abuse.
Pure narcotics, on the other hand, are often associated with opioid analgesics that act on opioid receptors in the brain to produce pain-relieving effects. However, in the context of this question, if by "pure narcotics" it is meant drugs that are not adulterated or mixed with other substances, they could still fall under the stimulant category if they stimulate the central nervous system.
In summary, based on their pharmacological effects and mechanisms of action, cocaine, pure narcotics (if they are CNS stimulants), and most amphetamines would be placed in the stimulant drug class.