From the airport
From the Berlin Brandenburg Airport BER Terminal 1-2: Take the Bahn RB23 direction Potsdam, that runs every 30 minutes, alight at "Alexanderplatz". From here take the M5 or M6 to "Klinikum im Friedrichshain". It's a 40 - 50 minute trip.
Taxi: From BER: it will take around 40 minutes and costs around €50-60.