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Clinical pharmacokinetics during plasma exchange.
F Fauvelle1, O Petitjean, M Tod
1Service de Pharmacie, CHI Le Raincy-Montfermeil, France.
Therapie
|September 1, 2000
Summary
Plasma exchange (PE) effectively removes drugs, especially those with low volume of distribution (Vd). An extracellular fraction index can predict drug removal efficiency during PE, guiding necessary dosage adjustments.
Area of Science:
- Pharmacokinetics
- Nephrology
- Internal Medicine
Background:
- Drug removal during plasma exchange (PE) is influenced by molecular pharmacokinetic properties.
- Plasma-protein binding and volume of distribution (Vd) are key factors affecting PE's drug removal efficiency.
- Previous studies have examined PE's impact on various drug classes, including antivirals and antibiotics.
Purpose of the Study:
- To evaluate the effectiveness of drug removal during PE.
- To identify predictive parameters for drug elimination during PE.
- To establish guidelines for dosage adjustments during PE.
Main Methods:
- Analysis of pharmacokinetic parameters influencing drug removal by PE.
- Evaluation of drug removal using parameters like extracorporeal clearance, half-life, and fraction eliminated (Fe).
- Establishing a linear relationship between Fe and the fraction of drug in extracellular fluids.
Main Results:
- PE most significantly impacts drugs with a low Vd, irrespective of protein binding.
- The fraction of drug eliminated (Fe) during PE is approximately one-seventh of the drug's extracellular fraction.
- An extracellular fraction index < 20 indicates low drug extraction, while an index > 20 suggests consequential elimination.
Conclusions:
- The extracellular fraction serves as a predictive index for drug removal during PE.
- Dosage supplementation may be necessary to maintain therapeutic drug concentrations.
- For drugs with a low Vd (< 0.3 L/kg), dosage adjustments are often required during PE.