Yes it can as it has an ingredient that competes for the liver enzyme needed to metabolize certain meds. However, unless you have severe liver disease, it would take about 15 grapefruits right before your med to have any real effect. Certain foods can do this too, like BBQ'd or grilled meat, but I have never seen this clinically be a problem. It is interesting in a biochemistry kind of way though. Look of CYP450/psych meds.