Introduction of ACE inhibitors in patients taking diuretics

Although a diuretic may be added to a patient on an ACE inhibitor, the practitioner must be cautious when starting an ACE inhibitor in patients already taking diuretics.

Hypotension, particularly with the first dose, and the risk of dangerous hyperkalaemia in patients taking potassium sparing diuretics has lead to the general recommendation that therapy be started in hospital.

Suitable patients with uncomplicated mild to moderate heart failure can be treated in general practice if they are very carefully supervised:

• potassium sparing diuretics should be discontinued from the regimen before starting an ACEI - changing to a loop diuretic alone. Potassium supplements should also be stopped.
• if possible try to reduce the dose of loop diuretics for a few days before starting therapy but beware severe rebound pulmonary oedema. In primary care, diuretics should be withheld for a brief period (at least 24 hours) to allow any volume depletion to resolve
• start with e.g. captopril (which has a short half life) 6.25mg morne or enalapril 2.5mg. With the patient recumbent, monitor the blood pressure carefully to detect the profound first dose hypotension which is common in patients taking loop diuretics.
• change if required to the preferred ACE inhibitor and increase therapy
• continue monitoring clinical progress, blood pressure electrolytes and renal function