ABSTRACT
The properties and pharmacological effects of drugs are due to their interactions with other molecules such as enzymes and receptors. Water solubility, which is a very important property of a drug, is based on interactions with water. Charge has a major effect on the properties of a drug. The presence of a charge not only increases water solubility, but also has a major effect on its absorption, distribution, and excretion, and many metabolic pathways introduce a charge onto a drug in order to increase excretion, especially renal excretion. In larger molecules, hydrogen bonds or even iondipole interactions can occur within the molecule such that they interact less with water or other molecules. An acid is any chemical entity that can donate a proton and a base is any chemical entity that can accept a proton. The conjugate acid of a weak base is a strong acid and the conjugate acid of a strong base is a weak acid.
