Hypertension has become a common phenomenon. Primary factors are fast going life and tensions to keep pace with it. All these factors accounts towards heavy Antihypertensive drugs usage worldwide. The excess intake of these drugs may cause many abnormalities. Methyldopa is an antihypertensive drug, and shows strong interaction with metals. Interactions of methyldopa with some biologically important metals i.e. iron, copper, cobalt, nickel and zinc was studied by potentiometric method. Theoretical stability constant values were calculated using potentiometric titration curves and were refined through computer program “BEST”. The stoichiometry of the studied complexes was found ML2 through potentiometric method. Logβ2 values were obtained 10.0, 8.10, 8.02, 10.0, 10.0 and 9.50 for Fe(II)-Methyldopa, Fe(III)-Methyldopa, Cu(II)-Methyldopa, Co(II)-Methyldopa, Ni(II)-Methyldopa and Zn(II)-Methyldopa complexes respectively.