DRUGS KNOWN TO AFFECT FOLATE METABOLISM (E.G., METHOTREXATE) AND THEIR DERIVATIVES SHOULD BE USED WITH CAUTION WHILE TAKING SAPROTERIN BECAUSE THESE DRUGS CAN DECREASE BH4 LEVELS BY INHIBITING THE ENZYME DIHYDROPTERIDINE REDUCTASE (DHPR).
CO-ADMINISTRATION OF SAPROTERIN WITH DRUGS THAT AFFECT NITRIC OXIDE-MEDIATED VASORELAXATION (E.G., PDE-5 INHIBITORS SUCH AS SILDENAFIL, VARDENAFIL, OR TADALAFIL), MAY HAVE ADDITIVE EFFECT ON BLOOD PRESSURE CAUSING HYPOTENSION. CO-ADMINISTRATION OF LEVODOPA AND SAPROPTERIN MAY CAUSE CONVULSIONS, EXACERBATION OF CONVULSIONS, OVER-STIMULATION, OR IRRITABILITY.