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Chemistry
Human Anatomy and Physiology

What is the osmolarity of albumin?

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March 04, 2008 4:51AM

Both 5% and 25% albumin USP have a calculated osmolarity near 300 mOsm/L. How do I calculate that? The package inserts for both strengths state they contain 145 mEq/L of sodium. Since for each cation there must be an anion, that puts the osmolarity at 290 mOsm/L. The contribution of albumin to the total osmolarity is minimal. One mole of albumin is about 70,000 grams, so a 50 mL vial of albumin 25% (12.5 grams albumin) would only contribute about 3.57 mOsm/L to the total osmolarity. Hospital pharmacists are warned not to dilute 25% albumin with water to make 5% albumin because the osmolarity of the final product is too low. - Marty, R.Ph.