Many drugs are stable in solution only at certain pHs or in narrow pH ranges. If a solution of one these drugs is desired, the manufacturer must find a way to maintain this certain pH over a period of time. This is accomplished by the use of buffer systems. A buffer is a solution of a weak acid and the salt of that weak acid (weak bases could also be used, but usually are not practical). The function of the buffer is to resist changes in pH by reacting with any hydrogen or hydroxyl ions that are added to the solution. Two of the most common buffer systems are:
Acetic Acid/Sodium Acetate. This is a common buffer found in many drug solutions.
Carbonic Acid/Sodium Bicarbonate. This is the buffer system that is most common in the fluids and tissues of the body and is used to keep the pH of the blood and body fluids constant.