Lisinopril monotherapy is an effective treatment of hypertension in once-daily doses of 10-80 mg, while hydrochlorothiazide monotherapy is effective in doses of 12.5-50 mg per day. In clinical trials of lisinopril/hydrochlorothiazide combination therapy using lisinopril doses of 10-80 mg and hydrochlorothiazide doses of 6.25-50 mg, the antihypertensive response rates generally increased with increasing dose of either component.

The side effects (see Error! Hyperlink reference not valid.) of lisinopril are generally rare and apparently independent of dose; those of hydrochlorothiazide are a mixture of dose-dependent phenomena (primarily hypokalemia) and dose-independent phenomena (e.g., pancreatitis), the former much more common than the latter. Therapy with any combination of lisinopril and hydrochlorothiazide may be associated with either or both dose-independent or dose-dependent side effects, but addition of lisinopril in clinical trials blunted the hypokalemia normally seen with diuretics.

To minimize dose-independent side effects, it is usually appropriate to begin combination therapy only after a patient has failed to achieve the desired effect with monotherapy.

Dose Titration Guided by Clinical Effect:   
A patient whose blood pressure is not adequately controlled with either lisinopril or hydrochlorothiazide monotherapy may be switched to lisinopril/HCTZ 10/12.5 mg or lisinopril/HCTZ 20/12.5 mg, depending on current monotherapy dose. Further increases of either or both components should depend on clinical response with blood pressure measured at the interdosing interval to ensure that there is an adequate antihypertensive effect at that time. The hydrochlorothiazide dose should generally not be increased until 2-3 weeks have elapsed. After addition of the diuretic it may be possible to reduce the dose of lisinopril. Patients whose blood pressures are adequately controlled with 25 mg of daily hydrochlorothiazide, but who experience significant potassium loss with this regimen may achieve similar or greater blood-pressure control without electrolyte disturbance if they are switched to lisinopril/HCTZ 10/12.5 mg.

In patients who are currently being treated with a diuretic, symptomatic hypotension occasionally may occur following the initial dose of lisinopril. The diuretic should, if possible, be discontinued for two to three days before beginning therapy with lisinopril to reduce the likelihood of hypotension. (See Error! Hyperlink reference not valid.). If the patient’s blood pressure is not controlled with lisinopril alone, diuretic therapy may be resumed.

If the diuretic cannot be discontinued, an initial dose of 5 mg of lisinopril should be used under medical supervision for at least two hours and until blood pressure has stabilized for at least an additional hour (See Error! Hyperlink reference not valid. and Error! Hyperlink reference not valid., Error! Hyperlink reference not valid.).

Concomitant administration of lisinopril and hydrochlorothiazide with potassium supplements, potassium salt substitutes or potassium-sparing diuretics may lead to increases of serum potassium (See Error! Hyperlink reference not valid.).

Replacement Therapy: The combination may be substituted for the titrated individual components.

Use in Renal Impairment: Regimens of therapy with lisinopril/HCTZ need not take account of renal function as long as the patient’s creatinine clearance is >30 mL/min/1.7 m2 (serum creatinine roughly ≤3 mg/dL or 265 µmol/L). In patients with more severe renal impairment, loop diuretics are preferred to thiazides, so lisinopril/HCTZ is not recommended (See Error! Hyperlink reference not valid., Error! Hyperlink reference not valid.).