
Interference with Laboratory Tests: Penicillins may interfere with urinary tests for fructose, aminolevulinic acid, estrogens, 17-hydroxycorticosteroids, protein, and sugar, with serum tests for uric acid; with biological tests for serum folate; and with serum electrophoresis.
Penicillins may decrease urinary excretion of aminohippurate sodium (PAH) and phenolsulfonphthalein (PSP) by competing for renal tubular secretion with these diagnostic agents.