Yes, but only with one class of medications - the immunosuppressants. Undenatured whey protein Immunocal helps improve your immune system and should not be taken if you are on any kind of immunosuppressant, for example after an organ transplant surgery, because Immunocal may counteract such medication.
There are no known interactions between Immunocal and any other prescription medications.
Also, note that as glutathione repairs your system, it starts functioning better. This can make some of your medications more effective over time (healing may be a long and gradual process). This means that your medications have to be monitored and dosages altered (lowered) as needed. If you are taking any prescription medications, you should always consult your doctor before starting any supplement.