⚠️ Research Use Only. Not validated for clinical diagnostic use.

Protein Binding Correction Calculator

Adjust antibiotic dose for highly protein-bound drugs. Free vs bound concentration.

Protein Binding Correction

Only unbound (free) drug is pharmacologically active. For highly protein-bound drugs, total dose must be higher to achieve target free concentration.

Total drug concentration (mg/L)

Protein bound fraction (%)

Target free concentration (mg/L)

Free Concentration

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Bound Concentration

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Required Total

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Adjustment Factor

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Binding Level	Free Fraction	Example
Low (<50%)	>50%	Most small-molecule drugs
Moderate (50–90%)	10–50%	Many antibiotics
High (>90%)	<10%	Warfarin, some fluoroquinolones

What is protein binding?

The fraction of drug bound to plasma proteins. Only unbound (free) drug is pharmacologically active.

Why correct for protein binding?

Highly protein-bound drugs (e.g. >90%) have very low free fractions, so the total dose must be higher to achieve the same free concentration.

How is free concentration calculated?

Free = Total × (1 − bound fraction). Bound = Total × bound fraction.