I've lived a very sheltered life, and a privileged one, too. It never occurred to me that solvent abuse was an option. But it seems that "Inhalation of butane can cause euphoria, drowsiness, unconsciousness, asphyxia, cardiac arrhythmia, fluctuations in blood pressure and temporary memory loss". Jakers! I can only imagine doing butane if I had a very short attention span and stopped reading the effects list immediately after "euphoria". Butane is readily absorbed through the lung epithelium and its solubility in water/plasma is about the same as oxygen [40mg/L], and like oxygen it can cross the blood-brain barrier and start tricking about with the neurotransmitters and their receptors.
The problem is that when "they" spray liquid butane directly down the gullet it gets colder as it vaporises and can deliver -20°C to the wet epithelium. That causes a laryngospasm as the vocal chords clamp shut to protect the even more delicate lung tissue from freezing. It's call SSDS sudden sniffers death syndrome and causes about half the deaths each year among the inhalant community.