Speed

Oral 11: Amphetamine arrives in the brain

Some of the blood containing amphetamine that exits from the heart via the aorta reaches the brain. It spreads through the brain via the capillaries.

After taking amphetamine by mouth, you experience the effects within 30 to 45 minutes. Because the molecules are only absorbed into the blood gradually in the intestines, they do not arrive in the brain all at once.

For this reason, you do not get a sudden, powerful effect (a ‘rush’) when you take amphetamine by mouth. That does happen if you inject it intravenously. The effect of speed taken by mouth is also weaker because all the amphetamine molecules first flow through the liver, where a small proportion of them are neutralised.