Serum uridine levels in patients receiving N-(phosphonacetyl)-L-aspartate.

Serum uridine levels of N -(phosphonacetyl)-l-aspartate-treated patients from Phase I and continuing trials receiving 1000 to 2000 mg/sq m/day were measured by reverse-phase high-pressure liquid chromatography. For the five patients studied, the predose serum levels ranged from 2.6 to 6.4 µm, well within the normal range of 1.9 to 8.9 µm. All serum uridine levels decreased in the first 24 hr, but the drop was quite variable (7 to 65%). Uridine levels in all five patients remained below predose levels, with the largest drop for each patient being 37 to 85% at differing time points. The only patient to show a daily decrease was the only responder and the patient with the largest decrease. N -(Phosphonacetyl)-l-aspartate appears to have a limited reductive effect on human serum uridine levels.