The drugs of abuse may give the user a feeling of pleasure, but it is important to remember that they are toxic substances. We are constantly being made aware that long-term drug abuse can be bad for our health and that even a single use of a drug can kill. But did you ever wonder HOW drugs kill?

The vast majority of drug overdose cases involve the use of more than one drug. In 2003 the Drug Abuse Warning Network reported an average of 2.7 drugs in fatal overdose cases. Importantly in these cases, no single drug is usually present at a lethal dose. Rather it is the synergistic effects of the drugs that is lethal. For example, a combination of heroin and alcohol can be especially dangerous. Heroin and alcohol both suppress breathing, but by different mechanisms.

Heroin and alcohol: a deadly combination

Excitatory signal

Inhibitory signal

Under normal conditions, excitatory and inhibitory signals are in balance, resulting in controlled, regular breathing.

Alcohol decreases the excitatory effects of glutamate.

Heroin increases the inhibitory effects of GABA.

Under the influence of alcohol or heroin, excitatory and inhibitory signals are out of balance, suppressing the impulse to breathe.

Heroin is the cause for more deaths by overdose than any other single drug. The majority of these deaths ultimately result from respiratory failure. A toxic dose of heroin increases the inhibitory effect of GABA, which causes breathing to slow and eventually stop.

Alcohol overdoses occur predominantly in two ways. First, by decreasing the excitatory effect of glutamate, alcohol causes unconsciousness. At high levels, it can also cause breathing to slow or cease. Second, the body tries to rid itself of unabsorbed alcohol by emptying the stomach. If a person vomits while they are unconscious, they may inhale the vomit and compromise their breathing or even drown.

We've all heard that cigarette smoking causes lung cancer and death, but can smoking also lead to a nicotine overdose? No, but it is possible to overdose on nicotine by using combinations of nicotine patches or nicotine gum and cigarettes at the same time. This combination puts much more nicotine into the body than smoking alone. Sometimes, nicotine can reach levels high enough to paralyze the muscles that control breathing or cause a heart attack.

Brain

Muscle

Brain

Muscle

Nicotine

. Stimulation of central nervous system
. Addiction

. No effect

. Confusion
. Seizure
. Coma

. Muscular twitching
. Muscle paralysis
. No breathing

At low concentrations, nicotine binds only to receptors in the brain.

At high concentrations, nicotine binds to receptors both in the brain and on muscles.

Stimulants such as cocaine and methamphetamine trigger the release of the adrenaline-like hormone norepinephrine, which causes:
. Increased motor activity
. Increased heart rate
. Increased blood pressure
. Narrowing of blood vessels

1. Brain damage
Increased blood pressure increases the risk of a ruptured blood vessel in the brain. Narrowing of blood vessels reduces blood flow around the brain.

2. Heart attack
Increased oxygen demand by the heart (because of increased motor activity) accompanied by reduced blood supply (narrowing of blood vessels) can lead to heart attack.

3. Overheating
One function of dopamine is to regulate body temperature. Altering dopamine levels with stimulants can affect the body's ability to cool itself. Combined with increased motor activity, this can lead to a dangerous increase in body temperature, resulting in organ failure and death.

Cocaine can kill in a variety of ways, most commonly heart attack, overheating (hyperthermia), and brain damage. After taking even a low dose of cocaine, you are 24 times more likely than normal to have a heart attack.

Because they are also stimulants, amphetamines increase levels of the neurotransmitter dopamine and the hormone norepinephrine. This can result in heart attack, overheating, and/or brain damage. Because the "club drug" ecstasy is often used in hot, overcrowded conditions where people are dancing, overheating is the most common result of an ecstasy overdose.