Stimulant drugs, or “uppers,” include cocaine and the amphetamines. Substances such as ephedrine, pseudoephedrine, and phenylpropanoloamine are also classified as stimulants.

These drugs are available as over-the-counter decongestants, diet aids, and stimulants. Caffeine, found in coffee, tea, colas, cocoa, and over-the-counter drugs, is also a stimulant.

Nicotine is included in this section since it has some stimulant properties and closely resembles the stimulants with respect to withdrawal symptoms and associated cravings.

All of the stimulants act in one way or another to increase the activity of a part of the central nervous system known as the sympathetic nervous system, which is what causes us to be on alert and produces the fight or flight reaction. It functions in a balanced fashion with the parasympathetic nervous system, which controls functions such as eating, digesting, and slowing the heart rate. Norepinephrine, which is closely related to adrenaline, is the main neurotransmitter involved in the activity of the sympathetic nervous system.

When your sympathetic nervous system is active, several things occur. Blood vessels in the gut constrict, leading to a reduced appetite. Blood flow to the brain and muscles increases. Your heart rate goes up, as does your blood pressure.

Pupils dilate, and in extreme cases your hair stands on end.

Your senses become more acute, and you are more alert. Your ability to concentrate goes up. To a mild degree, these effects are pleasurable to most people.

Caffeine, nicotine, and over-the-counter preparations produce these effects to a mild degree if they’re used in moderation. Cocaine and amphetamines are much more potent, and have much more potential for abuse. The use of intravenous or smoked forms of stimulants leads to an intense and highly addictive sensation and also to the development of cravings when the drug is stopped.

Stimulant addicts typically use in an episodic fashion. The user will binge for several days (periods called runs) and then crash. During the crash, the user will experience depression, fatigue, agitation, and craving. Cocaine or amphetamine addicts will often abuse depressant drugs, opiates, or alcohol during the crash to modulate the symptoms.

Cocaine
Cocaine is found naturally in the leaves of the coca plant, which grows in high altitude areas of South America. The ancient Incas chewed these leaves for their mild stimulant effect, which resembles that of a strong cup of coffee. The practice is still in effect.

The amount of drug that is delivered in this fashion is rather low, and it does not pose a major health problem. But distilling the active ingredient - cocaine - from the coca plant produces a much more potent substance.

Processed cocaine has been used for at least a century, for a variety of purposes.

When applied to tissue, cocaine produces local anesthesia.

A legitimate use of cocaine is found in the operating room.

Cocaine spray is applied before the insertion of breathing tubes used during surgery. Cocaine’s stimulant effects have also been long recognized. Sigmund Freud had advocated the use of cocaine for a variety of medical indications before coming to understand the drug’s addictive potential and retracting any such recommendations.

Cocaine acts directly on brain cells within the pleasure center by stimulating the release of dopamine and other neurotransmitters. It essentially overrides the natural control mechanisms of this system, which leads to the intensely pleasurable high but also to an eventual depletion of the stores of these chemicals. Cocaine users eventually lose the ability to feel this pleasurable sensation as the stores are depleted further and further and the brain becomes tolerant to the drug’s effects.

But the drug also sets up a strong conditioning effect leading to severe cravings. Within a short period of time, the user is caught between the strength of the cravings and the dull depression that results when the drug is not present in the system. It can take many months for the brain to build the stores of neurotransmitters back up. Irritability, severe depression, hallucinations, and delusions can result from the chronic use of cocaine. Sudden mood swings and episodes of uncharacteristic hostility and abusiveness may be observed by family members and coworkers who may be unaware of the addiction.

Cocaine is abused in several forms. Powder cocaine is inhaled nasally. The substance can be altered chemically through a process of free-basing and administered intravenously or by inhalation. Crack or rock cocaine is formed from powder cocaine, and comes in small crystals that resemble chunks of soap. These are burned in a pipe or another vehicle and inhaled. One crack rock can be relatively inexpensive, making them widely accessible, but it’s not uncommon for a crack addict to spend as much money as is available - and more - to repeat the brief high over and over again.

It has been something of a rule of thumb that most addicts have a particular drug of choice, or a category of choice. For example, people who do “downers” generally don’t like the effects of stimulants and vice versa. However, crack cocaine has proven to be the great leveler in this regard - when crack cocaine is available, many addicts of all types eventually end up using it primarily, while occasionally drinking or using other drugs such as the depressants to deal with side effects.