He wasn't making excuses, just explaining. Cocaine achieves its euphoric effects by prolonging chemical interactions in the tiny gaps between nerves, or neurons, in the brain. Neurons, unlike wires, don't actually touch. They are separated by infinitesimal gaps, where signals pass from one neuron to another. After doing their job, the chemicals are released back into the gap, to be swept up and used again by the first neuron.
Cocaine interrupts that cycle.
In effect it slams the pedal to the metal and holds it there. The brain's pleasure centers go wild, but supercharged neurons also zap the heart into overdrive and blast blood pressure through the roof. Cocaine is best known for its mental effects, but blood vessels take the hardest beating. Normally, nerves fine-tune arteries to relax or constrict in response to organ demand. Eat a big meal and your intestinal arteries open up.