Do people use it for sex somehow? What is the effect? Just in the book,"Fight Club", the author describes this drug in a sex related context.
Treats and prevents chest pain (angina pectoris).
And more pertinent for the question:
On the street, this medicine and others like it are sometimes called "poppers." They have been used by some people to cause a "high" or to improve sex. Use in this way is not recommended. Amyl nitrite can cause serious harmful effects if too much is inhaled.
Poppers are a name for inhaled nitrites which Amyl Nitrite is one of the most common. They can be lethal if used recreationally and cause vasodilation.
Poppers are rapid-onset, short-acting potent vasodilators that produce a rush characterized by warm sensations and feelings of dizziness. Poppers sometimes are used to facilitate anal intercourse because of their actions on the anal sphincter.
I have read reports about them being similar to Viagra and having a psychedelic effect. I have also included the Wikipedia link.