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Cardiac sensitization: methodology and interpretation in risk assessment
William J Brock1, George M Rusch, Henry J Trochimowicz
1ENVIRON Institute for Health Risk Sciences, 4350 N. Fairfax Drive, Suite 300, Arlington, VA 22203, USA. wbrock@environcorp.com
Regulatory Toxicology and Pharmacology : RTP
|July 25, 2003
Summary
Cardiac sensitization, an increased heart sensitivity to epinephrine (adrenaline), poses risks with hydrocarbon exposure. This study reviews methods for detecting cardiac sensitization and discusses their use in risk assessment.
Area of Science:
- Toxicology
- Cardiovascular Pharmacology
- Risk Assessment
Background:
- Cardiac sensitization, heightened heart sensitivity to epinephrine (adrenaline), is a known risk of hydrocarbon exposure, particularly halogenated hydrocarbons.
- This phenomenon can lead to fatal arrhythmias and necessitates critical blood levels of both the sensitizing agent and epinephrine.
- Historically, cardiac sensitization potential was assessed using exogenous epinephrine challenges in Beagle dogs during chemical inhalation exposure.
Purpose of the Study:
- To examine methodologies for detecting cardiac sensitization.
- To discuss the limitations and advantages of various cardiac sensitization detection methods.
- To evaluate concerns regarding the use of experimental data and physiologically based pharmacokinetic (PBPK) modeling for predicting exposure scenarios.
Main Methods:
- Review of historical and modified experimental methods for cardiac sensitization assessment in Beagle dogs.
- Analysis of the application of experimental cardiac sensitization data for risk evaluation, from semi-quantitative to quantitative regulatory purposes.
- Examination of the integration of physiologically based pharmacokinetic (PBPK) modeling in quantitative risk assessment for cardiac sensitization.
Main Results:
- Cardiac sensitization testing methods have evolved over 30 years, with modifications in the last 15 years for testing chlorofluorocarbon (CFC) replacements.
- Experimental data has transitioned from semi-quantitative occupational exposure risk evaluation to more quantitative regulatory use.
- The risks of cardiac sensitization from CFC replacements are presumed low, supported by earlier studies where dogs generated their own adrenaline.
Conclusions:
- Various methodologies exist for detecting cardiac sensitization, each with distinct limitations and advantages.
- The predictive accuracy of experimental cardiac sensitization data and PBPK modeling for real-world exposure scenarios requires careful consideration.
- Continued research and refinement of methodologies are crucial for accurate cardiac sensitization risk assessment, especially with new chemical entities like CFC replacements.