Abstract: Provided is a modified B-type natriuretic peptide (BNP) comprising a covalently attached polymer comprising amino acids, where the polymer inhibits degradation and/or elimination of the BNP in a subject, and where the modified BNP retains vasorelaxant activity. Nucleic acid molecules encoding the above-described modified BNP, as are vectors comprising the nucleic acid molecules, and cells comprising the vector. Methods of treating a subject suffering from or diagnosed with a disease, disorder, or medical condition that can be treated with a natriuretic, diuretic or vasorelaxant is also provided. The methods comprise administering the above modified BNP to the subject. Further provided is method of preparing the above-described modified BNP.