I quit drugs to inhale oxygen, deuterium and tritium, perhaps (8)
I believe the answer is:
isotopes
'deuterium and tritium perhaps' is the definition.
(deuterium and tritium are isotopes of hydrogen)
'i quit drugs to inhale oxygen' is the wordplay.
'quit' becomes 'stop' (synonyms).
'drugs' becomes 'es' (ecstasy tablets).
'to inhale' is an insertion indicator.
'oxygen' becomes 'O' (atomic symbol for oxygen).
'stop'+'es'='stopes'
'stopes' placed around 'o' is 'sotopes'.
'i'+'sotopes'='ISOTOPES'
(Other definitions for isotopes that I've seen before include "what may be used for diagnostic purposes" , "Poet is so confused about forms of chemical elements" , "Different forms of elements" , "Stoops, i.e. to become odd types of atoms" , "things that may be radioactive" .)