When the effects of speed are felt depends on the route of ingestion.
Amphetamine taken by mouth first enters the bloodstream via the intestines. It then travels to the liver and the heart and reaches the brain via the pulmonary circulation (heart-lungs-heart). Effects are felt some 30 minutes later.
When amphetamine is snorted, it enters the bloodstream via the nasal membranes. It travels to the heart and via the pulmonary circulation (heart-lungs-heart) to the brain. This route takes 2 to 3 minutes. Snorting speed carries greater risks than taking the drug by mouth.
When amphetamine is injected directly into a vein, it reaches the brain via the heart and the pulmonary circulation (heart-lungs-heart). Effects are perceivable within 15 to 30 seconds.