Lyric discussion by phillr 

Cover art for A Teenager in Love lyrics by Pains of Being Pure at Heart, The

This song is pretty obviously about a friend overdosing on heroin.

"now you feel ashamed but he feels nothing of the kind he talks of things he wouldn't mind to try sometime"

Is talking about how YOU feel ashamed for doing these drugs (heroin), and HE (the person who overdosed) not only doesn't see anything wrong with it, but is contemplating other drugs he wouldn't mind trying.