An drilling mud composition is described, which includes an aqueous base fluid, a viscosifier, and a weighting material The drilling mud composition also includes an anti-sagging agent that comprises a dimethylamino methyl ester, such as methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate. The anti-sagging agent may be used to prevent barite sagging, where barite is used as a weighting material. Small amounts of the anti-sagging agent may be used to maintain a low sag factor while drilling, and without causing unwanted increases in viscosity. The anti-sagging agent is effective for both vertical and inclined wellbores.