BIOELECTRICAL-IMPEDANCE ANALYSIS MEASUREMENTS FOR DRUG PHARMACOKINETICS

I review the rationale, methods, and existing data for using bioelectr ical impedance to determine drug pharmacokinetics. Because drugs distr ibute into body compartments after absorption, it is expected that bio electrical impedance measurements may correlate with drug pharmacokine tics (absorption, distribution, metabolism, and excretion). Authors ha ve examined correlations between total body water, extracellular fluid , and body cell mass and the drug volume of distribution or clearance and the elimination rate constant. Multiple-regression models with the all-subsets technique provided the most accurate equations with the l owest prediction errors and the highest correlation coefficients. Appl ication of bioelectrical impedance-derived equations to a different se t of patients allows prediction of pharmacokinetics. However, bioelect rical impedance equations do not yield more accurate dosing estimates than do standard dosing methods, and large dosing errors are possible in patients with aberrant physiology. Therefore, until multicenter tri als in large subject populations can provide stable, accurate equation s applicable to a wide variety of patient populations, bioelectrical i mpedance offers no advantage over standard pharmacokinetic dosing meth ods for the drugs studied.