The physical effects of inhalants vary because different inhalants combine different chemicals, and they produce different effects during and shortly after use.
Based on their studies of animals, scientists believe that, in general, when toxic vapors circulate to the brain, they depress the central nervous system. The action is similar to that of alcohol, sedatives, and anesthetics. Thus, many of the immediate physical changes inhalant users experience are similar to those caused by alcohol or anesthetics: Relaxation, slurred speech, slowed reflexes, lack of coordination, sleepiness, dizziness, headache, nausea, and vomiting. Abusers might also sneeze, cough, and drool.
Overdose can lead to a fast, irregular heart beat, which can be fatal--a syndrome called sudden sniffing death.
Toluene, an ingredient in many abused inhalants, possibly works on dopamine, a brain chemical involved in the pleasure producing effects of other abused substances. More research is needed to understand how inhalants produce their physiological effects.
Nitrites, used to enhance sexual experiences, are in a different category in terms of their effects. When inhaled, nitrates dilate the blood vessels and speed the heart's beating. As a result, abusers feel warm and excited for several minutes. They may also become flushed and dizzy, and may develop a headache.