Which medication will crystallize when mixed with D5NS?

Phenytoin is known to crystallize when mixed with certain intravenous solutions, including D5NS (5% dextrose in normal saline). This characteristic is particularly important for healthcare professionals to understand, as crystallization can lead to complications in the administration of the medication. When phenytoin is combined with dextrose-containing solutions, it can precipitate, leading to issues such as embolism if the precipitate enters the bloodstream.

The other medications in the choices, such as heparin, dopamine, and insulin, do not exhibit this same propensity to crystallize under similar conditions. Heparin is an anticoagulant that is stable in various IV solutions, dopamine is a vasoactive medication that remains soluble, and insulin typically remains in solution well when administered correctly. Understanding the solubility and compatibility of medications with IV solutions is crucial in ensuring safe and effective patient care.