Tissue-Drug Binding: Localization of Drugs and its Significance

Body tissues comprise 40-90% of body weight depending on body composition. They can serve as drug storage sites, competing with plasma binding sites.

Drugs can bind to different tissue components, enhancing drug distribution and localization.

Drug localization in tissues is influenced by factors like lipophilicity, drug structure, perfusion rate, and pH differences.

Most drugs bind primarily to the liver, followed by the kidneys, the lungs, and muscles.

Drugs exhibit tissue specificity. For instance, paracetamol binds to the liver, imipramine to the lungs, and chloroquine to the skin and eyes.

In prostate cancer treatment, estramustine, a nitrogen mustard-linked estradiol, selectively binds to the prostate, sparing normal cells.

Studies have shown that mexiletine when administered to lidocaine-treated patients, can displace lidocaine from tissue binding sites. This elevates plasma lidocaine levels but reduces its distribution to the lungs and kidneys.

So, using lidocaine loading doses with mexiletine potentially increases side effect risks.