Is a blood pressure of 190/128 of immediate concern in someone on antihpertensives?

Yes! Systolic BP (the upper number) should be less than 130 mmhg while on medications. Uncontrolled hypertension can lead to strokes, heart attacks and other bad problems. If you are on 3 or more meds for your bp, you may be a candidate for renal artery denervation. Get a home BP monitor and check your BP twice a day at random times, take this log to your doctor to get your BP down!
Stroke Potential. This is so high that you could have a stroke. It is an emergency whether you are on blood pressure medications or not.