Prevention of soman neurotoxicity by non-opioid antitussives.

The antitussives dextromethorphan (DM), carbetapentane (CBP), and caramiphen (CM) are known to have anti-convulsant properties. They were given individually to guinea pigs prior to poisoning with 2 x LD50 soman to test their efficacy against organophosphorus-induced convulsions, brain damage, and lethality. All subjects received an injection of pyridostigmine coincident with the antitussive, and were treated with atropine methylnitrate and pralidoxime chloride 30 sec after soman administration. CM, in a dose-dependent manner, protected against lethality and either prevented or reduced the intensity of convulsions, electrographic seizure activity (EGSA), and brain damage. CBP delayed the onset of EGSA and reduced its intensity. DM prevented EGSA at higher doses, but neither DM nor CBP protected against the lethal effects of soman. CM is known to possess relatively stronger anticholinergic properties than the other antitussives used in this experiment, which may have contributed to its relatively superior efficacy against soman.