The prevalence of cancer always increases every yearuntil it becomes the one of main health problems. Clinical study showed that β-Bloker had anticancer activity. β-Blocker was an antihypertensive drug that inhibited epinephrine and
norepinephrine. Both of these hormones played an important role in invasive, proliferation and metastasis cancer. Carvedilol was a non-selective β-Bloker class of drugs and also inhibited α-1 receptors which contain antioxidant. This study aims to determine the cytotoxic and antiproliferation effects of carvedilol with 5- fluorouracil on the growth of T47D breast cancer cells. The observation of cytotoxic effect was conducted to obtain IC50scores and the cell proliferation blocking (doubling time test) by using the MTT assay method. Cytotoxic test showed that carvedilol had potential cytotoxic activity (IC5018,05 μM atau 7,3399μg/ml). The combination of carvedilol and 5-fluorouracil at low concentrations had a synergistic effect (CI <1), at high concentration it hadadditive effect (CI=1).The combination of carvedilol with 5-Fluorouracil
showed an inhibitory effect on T47D cell proliferation but did not show a significant difference when compared to a single 5-FU. Based on the tests which have been conducted,the combination of carvedilol and 5-fluorouracil can improve the sensitivity of breast cancer cells to chemotherapy agent, so, it can increase the effectiveness of therapy and reduce the adverse side effects by reducing the use of 5-Fluorouracil chemotherapy doses.