Determination of pKa and Basic Drugs
- Calculating pKa is done through the formula pKa = pH + log (Acid/Base), also known as the Henderson-Hasselbalch equation. The equation shows the relationship between pH and pKa values as a measure of acidity.
- Basic drugs include amphetamines, erythromycin, caffeine, and theophylline. The rate of absorption in the body of drugs depends on pH of the body and the pH properties of the drug being administered. Basic drugs are absorbed at faster rate in areas of the body where pH is also basic. Basic pH in the body is around 7.4, any value greater than 7.4 is considered basic or alkaline.
- Basic drugs are absorbed more readily in basic environments in the body. In contract, basic drugs are absorbed slowly in acidic environments. Therefore in cases where there is an overdose of basic drugs, treating with a weak acid prevents toxicity by decreasing the absorption rate of the basic drug.
