A method of increasing a solubility of a manganese oxide includes contacting the manganese oxide with an acid component in the presence of a dissolution accelerator that includes at least one of hydrazine, a hydrazine derivative, or a hydrazide. Also disclosed is a drilling fluid containing a carrier; MnO2; and at least one of a viscosifier, a rheology modifier, a dispersant, a weighting agent, a defoamer, a fluid loss agent, bentonite, or a lubricant.