When drugs get into the bloodstream they are carried to all parts of the body and some reach the brain. The quicker the drug reaches the brain, the more intense the effects. The quickest way to get a drug into the brain - and also the most dangerous way of using any drug - is to inject it intravenously, or into the vein. Almost as quick is smoking a drug. followed by sniffing or snorting and then by mouth. Eating or drinking a drug is the slowest route, because the drug has to pass through the stomach first.
Once in the brain drugs affect chemicals called neurotransmitters. These are the chemicals that control the flow of information within the brain between the neurons or brain cells, forming a synapse. Neurotransmitters also alter people's moods and feelings. Different drugs can affect different neurotransmitters. For example, ecstasy appears to affect a neurotransmitter called serotonin by reducing the amount of the chemical in the brain. Those people with lower levels of serotonin in the brain tend to suffer from depression and also there are concerns that taking too much ecstasy for too long might make a person chronically depressed.
Experiments with animals have shown that certain drugs like ecstasy can damage brain cells but experts are not agreed on whether this happens with humans to the same extent. There have been concerns about damage to the brain from taking a wide range of drugs including ecstasy, LSD and solvents but the evidence is, so far, inconclusive. However, excessive and long-term use of alcohol has been shown to lead to possible brain damage.
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How do drugs affect the heart?
Once drugs are taken and enter the bloodstream the heart pumps blood containing the drug to the brain where it will affect how people feel.
Drugs can also have an affect on the heart directly and exacerbate heart disease. Heavy drinking of alcohol, for example, can weaken the heart's ability to pump blood and lead to heart failure although some studies have suggested that moderate consumption may be better for the heart than not drinking alcohol at all.
Taking regular and high doses of stimulant drugs like amphetamine, cocaine/ crack, ecstasy, anabolic steroids and even possibly caffeine may increase the risk of heart attacks, especially for people who already have heart problems or high blood pressure.
Heavy tobacco use can also lead to greater risk of heart problems. Nicotine, as a kind of stimulant, increases the workload of the heart, while carbon monoxide deprives the heart of the oxygen it needs. Smoking also tends to thicken the blood hence making it less able to flow through narrowed arteries.
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The effects of drugs on the liver
The liver breaks down or alters the chemical structure of drugs, gradually neutralising the affects of the drug.
Excessive, long term drinking of alcohol can result in damage to the liver, including cirrhosis, which can be fatal.
Suggestions that ecstasy use can damage the liver have been made but research is, so far, inconclusive.
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The effects of drugs on the lungs
Because the lungs provide the oxygen directly and very effectively to the body, anything that is inhaled similarly enters the blood and ultimately the brain very quickly. This is most promounced in drugs that are normally snorted but are chemically altered to make them more smokable, such as cocaine into crack and amphetamine into methamphetamine. The lungs' ability to absorb large amounts of these drugs in a short space off time, roughly 8 seconds, mean that the effects can be almost instant and very powerful.
Some drugs can also be inhaled, such as solvents and poppers/nitrites Again, the solvents are absorbed into the lungs almost instantly.
Another, relatively more dangerous, method is insuffelation. This is the method often used by asthma sufferers when using inhalers, where a fine spray is rapidly inhaled into the...