Evidence-based Toxicology

OVERVIEW

• much of what we do in toxicology is because we think it works, not because we know it works
• clinical toxicology has traditionally been based on animal studies, case reports and case series based on clinical observation rather than clinical trials
• as such the overall evidence base is weak
• an increasing number of new synthetic street drugs are being used recreationally with little prior scientific study

BARRIERS TO HIGH QUALITY EVIDENCE

• very few newly synthesised chemicals undergo RCTs to determine their effects on humans
• there are few validated animal models for toxicology research
• ethical considerations prevent volunteers from being subjected to known toxic agents as part of a clinical trial
• mortality is of little use in clinical toxicology as the cas fatality rate in the West is only 0.5% – most patients who make it to hospital survive
• intoxicated and/or suicidal patients usually lack the capacity for informed consent
• poison center registries have many limitations:
  — limited to acute toxicity
  — dependent on individuals to report cases
  — severely under-report overdose fatalities

SOURCES OF EVIDENCE

RCT

• RCTs remain the gold standard
• infeasible for many problems in clinical toxicology

Observational studies and data registries

• routine prospective clinical data collection in a database is the optimal way of conducting observational studies in clinical toxicology

Case reports and case series

• limited as they are subject to uncontrolled biases and tend to emphasize the bizarre
• useful for recognition and description of new toxic agents and manifestations
• useful for recognition of adverse events and rare manifestations
• useful for education

Other sources

• understanding of novel recreational agents can be obtained from lay websites such as Erowid

References and Links