Protein Binding

This version of the course is no longer available.
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Pharmacology in the Clinical Lab: Therapeutic Drug Monitoring and Pharmacogenomics (retired 10/15/2012). Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Pharmacology in the Clinical Lab: Therapeutic Drug Monitoring and Pharmacogenomics (retired 10/15/2012) (online CE course)
Protein Binding

Most drugs are bound to proteins when they circulate in the body.

  • Albumin is a major drug-binding protein in serum.
  • Albumin is an alkaline protein, so acidic and neutral drugs primarily bind to it.
  • If albumin binding sites become saturated, acidic and neutral drugs can bind to lipoproteins.
  • Alkaline drugs tend to bind to globulins, particularly to the globulin, alpha-1 acid glycoprotein.
  • Only free, unbound drugs are able to bind drug receptors and have therapeutic effects.

An equilibrium exists in the systemic circulation between a free and protein-bound drug and between a free and receptor-bound drug. This is illustrated in the image to the right.