Dissolution of phenytoin precipitate with sodium bicarbonate in an occluded central venous access device

To report a case of restored patency of a central venous access device occluded by precipitate of phenytoin sodium injection.

A patient experienced total occlusion of an implanted subcutaneous port caused by precipitation of phenytoin. Phenytoin sodium injection was mixed inadvertently with dextrose 5% in NaCl 0.45% injection during intravenous administration. Dextrose 5% in NaCl 0.45% injection, which is acidic (pH 4.0), caused the phenytoin sodium injection, a basic solution (pH 12.0), to precipitate. Local instillation of sodium bicarbonate 8.4% injection to decrease the pH of the medium restored patency of the occluded port.

There are reports of local instillation of solvent restoring central ports occluded by lipid-containing parenteral nutrient admixture, calcium phosphate salt precipitate, and coagulated blood. No report of local instillation into an occluded port to dissolve precipitate of phenytoin could be found. Several factors are involved in the precipitation and dissolution of phenytoin. The key factor in this case was the hydrogen ion concentration (pH) of the solution. Decreased pH caused the precipitation, but increased pH caused the dissolution of the precipitate of phenytoin.

Sodium bicarbonate injection was a suitable agent for clearing precipitate of phenytoin in this case of an occluded implanted central venous access device.