Here's a new study from the Division of Emergency Medicine at Washington
University, drawing on a large toxicology database, looking at the
treatment of patients with anticholinergic toxicity. From the paper:
The anticholinergic
toxidrome is well described and relatively common. Despite
controversy, studies have shown that physostigmine is relatively safe
and effective in reversing this toxidrome. We would expect
toxicologists would be liberal in its use. We retrospectively
analyzed data in the Toxicology Investigators Consortium (ToxIC)
registry, representing data from medical toxicologists in multiple
institutions nationwide, searching for patients who exhibited an
anticholinergic toxidrome, determining what treatment(s) they
received, and classifying the treatments as physostigmine,
benzodiazepines, physostigmine and benzodiazepines, antipsychotics,
or no definitive treatment. The causal agents of the toxidrome were
as reported by the treating toxicologist. Eight hundred fifteen
consecutive patients with anticholinergic toxidromes were analyzed.
Benzodiazepines alone were given in 28.7 %, 12.4 % were given
physostigmine alone, 8.8 % received both physostigmine and
benzodiazepines, 2.7 % were given antipsychotics, and 47.4 % were
given no definitive treatment. In patients who received only
physostigmine, there was a significant difference in the rate of
intubation (1.9 vs. 8.4 %, OR 0.21, 95 % CI 0.05-0.87) versus other
treatment groups. Physostigmine was given at varying rates based on
causative agent with use in agents with mixed or unknown effects
(15.1 %) being significantly lower than those with primarily
anticholinergic effects (26.6 %) (p less than 0.001). Patients
with anticholinergic toxicity were more likely to receive
benzodiazepines than physostigmine. Those patients who received only
physostigmine had a significantly lower rate of intubation.
Physostigmine was more likely to be used with agents exerting
primarily anticholinergic toxicity than in those agents with multiple
actions.
Physostigmine is
making a comeback for this indication. It appears to be safe and
very effective (markedly reduces the intubation rate) for patients
with a pure anticholinergic toxidrome. Conservative use reported in
the article for patients with a mixed toxidrome probably reflects
hesitancy to use it in cases of TCA overdose where physostigmine
carries a risk of adverse cardiac effects and seizures. I previously
blogged this topic here.