pH Adjusting Database

Last Review: August 2005

The pH is important in aqueous, drug-product formulation, especially since it involves drug solubility, activity, absorption, stability, sorption and patient comfort. The pH is also related to certain physical characteristics, such as the viscosity of some polymers used as gel-forming agents and in suspensions. The pH is adjusted by using acidifying and alkalizing agents. Acidifying agents are used in a formulation to lower the pH and alkalizing agents are used to increase the pH.

For all the reasons cited above, many times a formulation may already contain one of these agents to achieve a desirable pH. In all cases, before finishing up preparing a formulation that contains water, the pharmacist must check the pH and adjust it, if needed. Generally, because of easy incorporation, freshly prepared solutions of these agents can be used to adjust pH in such formulations.

The USP XXVIII/NF 23 specifically lists 14 acidifying agents and 9 alkalizing agents although other agents can also be used for their pH-altering effect.

Acidifying Agents

Select an agent by clicking on the name
Acetic Acid, glacial, USP	Acetic Acid, NF	Citric Acid, anhhydrous USP
Citric Acid, monohydrate USP	Fumaric Acid, NF	Hydrochloric Acid, diluted, NF
Hydrochloric Acid, NF	Lactic Acid, USP	Malic Acid, NF
Nitric Acid, NF	Phosphoric Acid, NF	Phospohoric Acid, diluted, NF
Propionic Acid, NF	Sodium phosphate monobasic, NF	Sulfuric Acid, NF
Tartaric Acid, NF

Alkalizing Agents

Select an agent by clicking on the name
Ammonia solution, strong, NF	Ammonium carbonate, NF	Diethanolamine, NF
Monoethanolamine	Potassium hydroxide, NF	Sodium bicarbonate, USP
Sodium borate, NF	Sodium carbonate, NF	Sodium hydroxide, NF
Sodium phosphate dibasic, USP	Trolamine, NF