Chronic Heart Failure: In chronic heart failure patients, worsening cardiac failure or fluid retention may occur during up-titration of Duobloc. If such symptoms occur, diuretics should be increased and the dose should not be advanced until clinical stability resume. Occasionally, it may be necessary to lower the dose or, in rare cases, temporarily discontinue it. Such episodes do not preclude subsequent successful titration of Duobloc. It should be used with caution in combination with digitalis glycosides, as both medicines slow AV conduction.