Sounds like some planned, but unimplemented feature.
} else if (stim < -200 || get_painkiller() > 240) {
add_msg_if_player(m_bad, _("Your breathing stops completely."));
add_memorial_log(pgettext("memorial_male", "Died of a drug overdose."),
pgettext("memorial_female", "Died of a drug overdose."));
hp_cur[hp_torso] = 0;
No. It only matters how much painkiller effect you have, not how much of it actually does something.