Experimental diazepam intoxication in rodents: physostigmine and naloxone as potential antagonists.

The ability of physostigmine and naloxone to reverse the loss of righting reflex (LRR) induced by diazepam was tested in mice and rats. Physostigmine was ineffective under our test conditions, but high doses of naloxone reduced the duration of LRR in both species. However, the LD50 of diazepam in mice was unaltered by 100 or 150 mg/kg of naloxone given 1 hr after LRR to model an antidotal situation. Use of a longer duration narcotic antagonist, naltrexone (172 mg/kg), in the same design likewise failed to elevate the LD50 for diazepam. These data give limited support to prior suggestions for clinical usefulness of naloxone, although not for physostigmine, in the management of intoxication caused by diazepam.