Methamphetamine and its effect on the brain:
Images courtesy National Institute on Drug Abuse
As with most psychoactive drugs, methamphetamine is highly soluble in fat when compared to its solubility in water. This allows it to easily cross cell membranes in the cerebral capillaries and reach the brain where it exerts its effect. However, if methamphetamine is administered in tablet or capsule form then it must be able to dissolve in water when it enters the stomach or intestine, because only dissolved drug molecules can pass into the blood stream and reach the brain.
Both the rush (produced by smoking and injecting) and the high (produced by snorting and swallowing) are believed to result from the release of very high levels of the neurotransmitter dopamine into areas of the brain that regulate feelings of pleasure. The large release of dopamine produced by methamphetamine is thought to contribute to the drug’s toxic effects on nerve terminals in the brain, with regular abuse leading to possible memory and concentration impairment, chronic mental health effects, and “jerky” physical motions.
Long-term methamphetamine abuse can also result in addiction. Addiction is a chronic, relapsing disease, characterized by compulsive drug-seeking and drug use which is accompanied by functional and molecular changes in the brain. Studies on animals have shown extensive damage (up to 50 percent) to dopamine-producing brain cells after prolonged exposure to low levels of methamphetamine. Researchers also have found that serotonin-containing nerve cells may be damaged even more extensively. Whether this toxicity is related to the psychosis seen in some long-term methamphetamine abusers is still an open question.