Kinkade had died of “acute ethanol and diazepam intoxication”—alcohol and Valium.
1961, from (benzo)diazep(ine) + -am, apparently an arbitrary suffix. The element diazo- denotes two nitrogen atoms combined with one hydrocarbon radical.
diazepam di·az·e·pam (dī-āz'ə-pām')
A tranquilizer used in the treatment of anxiety and tension and as a sedative, a muscle relaxant, and an anticonvulsant.