Methods of drug administration in order of fastest to slowest CNS response
Intravenous (IV) drug use in which the drug is injected directly into a vein and enters the bloodstream to reach the brain. This is the quickest way of achieving a psycho-active drug effect. The drug effect is experienced in less than one minute.
Inhaling or breathing a volatile substance such as petrol or nitrous oxide (also known as laughing gas) is almost as fast as IV drug use, because the gaseous molecules travel easily and quickly through the cell walls from the lungs into the bloodstream.
Snorting or sniffing a powdered drug such as cocaine or amphetamine (speed) also results in rapid drug effect, as the drug is absorbed quickly through the mucous membranes inside the nose into the bloodstream; the effects can be felt in two minutes.
Smoking a burnt substance such as cannabis or tobacco also results in a rapid onset of a drug effect. However it is not as fast-acting as volatile substances (e.g. petrol), as the tiny particles in the smoke do not pass from the lungs into the bloodstream with the ease of inhalants.
Swallowing a drug is a relatively slow method of taking a drug. After the drug is swallowed, it is dissolved in the stomach and then absorbed into the bloodstream from the linings of the stomach and later, the small intestine. Alcohol produces drug effects in five/ten minutes, as it is already in liquid form and passes from the stomach into the bloodstream. Drugs in tablet form can take over an hour for the onset of the drug effect.
Rectal use of a drug involves the insertion of the drug into the rectum, where it can dissolve and be absorbed into the bloodstream via the linings of the rectum. In medical use, drugs are sometimes administered this way to patients who cannot swallow. Recreational use of this type of administration is not widespread. Absorption is usually relatively slow.
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