По време на изследвания in vitro клонирани човешки сърдечни калиеви канали (hERG) са били инхибирани с високи концентрации нелфинавир и активния му метаболит М8.
During in vitro studies, cloned human cardiac potassium channels (hERG) were inhibited by high concentrations of nelfinavir and its active metabolite M8. hERG potassium channels were inhibited by 20% at nelfinavir and M8 concentrations that are about four- to five-fold and seventy-fold, respectively, above the average free therapeutic levels in humans.