USP <785> - Osmolality and Osmolarity

What it says

Osmolality and osmolarity of a formulation must be measured using appropriate, validated methods, particularly important for parenteral and ophthalmic products where a mismatch with physiological tonicity can cause patient discomfort or tissue damage upon administration.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• Osmolality testing connects directly to patient comfort and safety at the point of administration, an injectable or ophthalmic product with inappropriate tonicity can cause pain, tissue irritation or hemolysis regardless of how well it otherwise meets its chemical specifications.
• This measurement is particularly relevant for formulations intended for sensitive administration routes, including ophthalmic, intrathecal and certain parenteral products, where the margin for tonicity deviation is narrow.
• A formulation change involving excipients that affect osmotic contribution, even one not intended to change tonicity, can shift osmolality enough to warrant retesting.

What inspectors look for

• Whether osmolality or osmolarity testing was performed on formulations intended for sensitive administration routes where tonicity affects patient comfort or safety.
• Whether formulation changes affecting osmotic contribution were evaluated for their impact on measured osmolality before being implemented.
• Whether the test method used is validated and appropriate for the specific formulation type being measured.

Related regulations