HOW CRACK WORKS

Once in the bloodstream, it speeds to the brain's pleasure centre to
deliver a fleeting high

Crack cocaine makes you feel like a new man; the only problem is the
new guy wants more cocaine. That maxim, part of a 1990s public service
campaign in the United States, conveys a hard truth: crack delivers an
intense but brief high that can trigger powerful cravings for more
stimulation.

Crack invaded inner cities in the mid-1980s, offering a cheap
alternative to the powdered form of cocaine. More than two decades
later, crack remains a central feature of the drug landscape in Ottawa
and other North American cities.

The physiology of crack use helps to explain why it has become so
firmly entrenched.

Crack speeds delivery of cocaine's powerful chemical impact. When a
rock of crack is heated - usually in a small glass pipe - it produces
smoke that's drawn into the lungs. The lungs are super efficient at
transferring the vapourized cocaine from air sacs (alveoli) to tiny
blood vessels (capillaries).

Once in the bloodstream, the drug is whisked to the brain's main
pleasure centre within seconds.

That centre, known as the ventral tegmantal area (VTA), is made up
neurons in the middle of the brain. The centre is vital to the
survival of the human species since it generates a pleasurable
sensation for behaviour that sustains people - eating, drinking, sex.

An evolutionary feature, the system reinforces essential human
behaviour with what amounts to brain candy: dopamine. That chemical
messenger informs other parts of the brain's reward circuit that the
body's fundamental needs are being met.

The cocaine molecule produced by smoking crack hijacks this reward
system.

Cocaine overstimulates the circuit by preventing dopamine from being
reabsorbed by those neurons that first issued the neurotransmitter. As
a result, the brain is flooded with dopamine that continues to send
its euphoric message to other neurons.

Crack's impact on brain chemistry means users can also experience
surges in confidence and energy. But the high, while quickly
delivered, is fleeting: a typical hit lasts anywhere from five to 15
minutes.

As it works on the brain, cocaine also changes the body. Its
short-term effects include constricted blood vessels, dilated pupils
and an increase in the body's heart rate, respiratory rate,
temperature and blood pressure. Some people become agitated or nervous
under influence of the drug. In rare cases, first-time cocaine users
can suffer fatal effects.

"Cocaine-related deaths are often a result of cardiac arrest or
seizures followed by respiratory arrest," according to a 2009 research
report by the U.S. National Institute on Drug Abuse. "Research has
also revealed a potentially dangerous interaction between cocaine and
alcohol. In fact, this mixture is the most common two-drug combination
that results in drug-related death."

Not everyone who smokes crack becomes addicted. But because the drug
produces such a quick, intense high, it is dangerous, particularly to
those with a genetic predisposition to addiction.

Studies have shown that people with naturally low dopamine levels -
those with depression often suffer the condition - experience more
intense highs from stimulants such as crack.

"So if you have a genetic predisposition, you get a bigger bang for
your buck whenever you use the drug: You get a greater amount of
dopamine released," explains Dr. Peter Selby, clinical director at
Toronto's Centre for Addiction and Mental Health.

Cocaine can cause people to "crash" when they stop using it, he said,
because they move quickly between euphoria and irritability. That can
bring powerful cravings for more of the drug, which in turn can lead
to binges and addiction.

The physiological effects of longterm crack use are
profound.

The brain can develop an increased tolerance to the drug that requires
users to smoke more crack to obtain the same high. Computer imaging
has revealed that cocaine physically alters the brain: the number of
available dopamine receptors is significantly reduced in an addict.