Ecstasy Gets Into the Brain Very Easily
The chemical structure of ecstasy allows it to reach the brain quickly after ingestion. First, the pill is ingested and it disintegrates quickly in the stomach contents. Once dissolved, some ecstasy molecules are absorbed from the stomach into the bloodstream, but most of the ecstasy molecules move from the stomach into the small intestine. There, they are absorbed into the bloodstream very easily.
The following explanation will be more easily understood by those who have had some chemistry:
Ecstasy is a weak base--this means that ecstasy is likely to "pick up" or accept a hydrogen ion (H+) from the surrounding medium (the gastric acid in the stomach is loaded with H+). After the ecstasy has accepted a H+, it has a charged (or polar) character, which makes it difficult to cross a biological membrane. Biological membranes have a nonpolar core, so compounds having a nonpolar nature are more likely to diffuse across the membrane (passive diffusion). Therefore, most of the ecstasy is not absorbed from the stomach into the bloodstream. Rather, the ecstasy molecules get emptied from the stomach into the small intestine. In the small intestine the more alkaline environment causes ecstasy to give up its H+, becoming more nonpolar. The large surface area and the more alkaline environment enable the ecstasy molecules to diffuse across the membrane into the blood capillaries very quickly.
Ecstasy molecules that have entered the bloodstream from the stomach and small intestines then travel to the liver. In the liver, some of the ecstasy is metabolized to inactive compounds and the rest is carried through the veins to the heart. Once in the heart, the ecstasy is pumped to the lungs along with the blood, which becomes oxygenated and then returns to the heart. Now, oxygenated blood carries the ecstasy from the heart to the brain and to other organs in body that have a high blood flow. Normally there is a barrier between the blood vessels in the brain and brain matter, which excludes many drugs from entering the brain. However, ecstasy is predominantly in its nonpolar form in blood and therefore it crosses the barrier into the brain very easily. It will take about 15 minutes for ecstasy to reach the brain if taken on an empty stomach.
Source: National Institute on Drug Abuse