Types of studies used to support treatment recommendations in medical toxicology

There are few controlled clinical trials in medical toxicology to guide treatment decisions. Given the relative paucity of definitive data, we determined the types of evidence used to support treatment recommendations given in three major toxicology textbooks. One author reviewed the acetaminophen, tricyclic antidepressant, calcium channel blocker plus any relevant antidote chapters in three textbooks: Goldfranks Toxicologic Emergencies, Critical Care Toxicology, and Medical Toxicology. We identified statements that gave a treatment recommendation and classified the citation using the following system: No citation, general review article, in vitro study, animal study, case reports (n<3), case series (n>2), retrospective study, prospective observational study, and controlled clinical trial. Proportions for each type of citation with 95% confidence intervals were determined. We identified 469 treatment recommendations. We could not classify 57/742 citations. A large number of statements were not referenced (14%, 95% CI 12-17%). The most common citation types were case reports (28%, 95% CI 25-31%) and animal studies (18%, 16-21%). The proportions for the remaining types of citations were: review article (9%, 7-11%), clinical trials (9%, 7-11%), retrospective studies (8%, 6-10%), prospective observational studies (5%, 3-6%), and case series (4%, 3-6%). There is a need for more systematic studies of poisoned patients. As case reports are commonly used to support treatment recommendations, they should be held to rigorous scientific standards and include information to assess the validity of the conclusions. Case reports and animal studies are commonly used as evidence to support treatment recommendations in medical toxicology textbooks.