Nur Coffein macht einen bestimmten Effekt des Creatins zunichte ("dynamic torque production").. Zumindest in hohen Dosen (50mg/kg):

"The data show that Creatine supplementation elevates muscle phosphocreatine concentration and markedly improves performance during intense intermittent exercise. This ergogenic effect, however, is completely eliminated by caffeine intake. PMID: 8929583"