Bisoprolol Fumarate and Hydrochlorothiazide have been used individually and in combination for the treatment of hypertension. The antihypertensive effects of these agents are additive; Hydrochlorothiazide 6.25 mg significantly increases the antihypertensive effect of Bisoprolol Fumarate. The incidence of hypokalemia with the Bisoprolol Fumarate and Hydrochlorothiazide 6.25 mg combination is significantly lower than with Hydrochlorothiazide 25 mg. Bisoprolol Fumarate is a _1-selective (cardioselective) adrenoceptor blocking agent without significant membrane stabilizing or intrinsic sympathomimetic activities in its therapeutic dose range. Hydrochlorothiazide is a benzothiadiazine diuretic. Thiazides affect renal tubular mechanisms of electrolyte reabsorption and increase excretion of sodium and chloride in approximately equivalent amounts