RESUMEN
OBJECTIVE: We determined the influence of 3-OMD in the protein binding of levodopa to estimate the effect of 3-OMD on the penetration of levodopa into brain. METHOD: P-glycoprotein in the brain may serve to limit drug penetration into the brain. Because it is not available as an experimental substance, but has similar binding properties with alpha 1 acid glycoprotein(AGP), we used AGP in this study. Additionally, we used blood plasma to see the affinity of plasma binding of levodopa. The final concentration of chemicals used in this study were 125, 250, 500, 1000, 2000, 4000 microgram/l for levodopa and 0, 1250, 5000, 10,000 microgram/l for 3-OMD, 1 mg/l for AGP. The free fraction of levodopa in blood plasma and AGP were separated by ultrafiltration method and determined by beta-counter, respectively. RESULTS: We found that levodopa did not bind with AGP, but only 22-24% from 125 microgram/l to 4000 microgram/l of it bound with blood plasma. The addition of 3-OMD to the blood plasma did not significantly change the binding of levodopa. CONCLUSIONS: We can conclude that 3-OMD does not influence the penetration of levodopa into brain. These small amount of the binding does not expect to influence to other drugs on the binding with plasma.