What is the significance of unbound drug concentration in plasma water in relation to systemic drug action?
Understand the Problem
The content discusses the concept of dynamic equilibrium in a systemic action context, particularly focusing on how blood composition affects drug concentration and its measurement at the site of action.
Answer
Unbound drug concentration determines efficacy as only unbound drugs reach the site of action.
The unbound drug concentration in plasma water is crucial as only unbound drugs can pass through the capillary endothelium to reach the site of action, determining the drug's efficacy. This measurement, however, is complex because drugs can bind to blood cells and proteins in the plasma, potentially skewing effectiveness assessments.
Answer for screen readers
The unbound drug concentration in plasma water is crucial as only unbound drugs can pass through the capillary endothelium to reach the site of action, determining the drug's efficacy. This measurement, however, is complex because drugs can bind to blood cells and proteins in the plasma, potentially skewing effectiveness assessments.
More Information
The unbound drug is the pharmacologically active form since it can diffuse into tissues to exert its therapeutic effect, making its concentration a critical factor in drug efficacy.
Tips
Confusing total drug concentration with unbound drug concentration can lead to inappropriate dosing decisions. Remember, only unbound drug can exert a pharmacological effect.
Sources
- Drug Distribution to Tissues - Merck Manuals - merckmanuals.com
- Importance of Relating Efficacy Measures to Unbound Drug ... - NCBI - ncbi.nlm.nih.gov
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