Can Hydrochlorothiazide (HCT) and Lisinopril be given together?

Lisinopril and Hydrochlorothiazide (HCT) Combination Therapy

Yes, lisinopril and hydrochlorothiazide can be safely and effectively given together, and this combination is actually recommended for many patients with hypertension who need additional blood pressure control. 1

Evidence Supporting Combination Use

• Lisinopril-hydrochlorothiazide is a well-established combination that appears in clinical guidelines as a fixed-dose combination option for hypertension management 1
• The combination is available as fixed-dose formulations under trade names like Prinzide and Zestoretic in various dosage combinations (10/12.5,20/12.5,20/25 mg) 1
• The combination provides complementary mechanisms of action, where thiazide diuretics may stimulate the renin-angiotensin-aldosterone system while ACE inhibitors block this system, resulting in additive blood pressure-lowering effects 1

Clinical Efficacy

• When given together, the blood pressure lowering effects of lisinopril and hydrochlorothiazide are approximately additive 2
• In clinical trials, the combination therapy effectively controlled blood pressure in approximately 81.5% of patients with mild, moderate, and severe hypertension 3
• The combination allows for lower doses of each individual medication while maintaining efficacy, with mean antihypertensive doses of lisinopril being lower when given with hydrochlorothiazide than when given alone (48 mg vs. 68 mg daily) 4
• Long-term studies (52 weeks) have shown that the combination was superior to either agent alone in controlling diastolic blood pressure 5

Metabolic Considerations

• Lisinopril can help mitigate some of the adverse metabolic effects of hydrochlorothiazide 6
• When lisinopril is used alone, there's a mean increase in serum potassium of approximately 0.1 mEq/L, while the combination with hydrochlorothiazide results in a mean decrease of 0.1 mEq/L 2
• Thiazide diuretics can increase serum glucose, but this effect may be partially offset by ACE inhibitors like lisinopril 1
• In ALLHAT, diabetes incidence after 4 years was 11.8% with chlorthalidone therapy compared to 8.1% with lisinopril, suggesting ACE inhibitors may have a more favorable metabolic profile 1

Safety Profile

• The combination of lisinopril and hydrochlorothiazide is generally well-tolerated 6
• Common adverse effects include dizziness (7.5%), headache (5.2%), cough (3.9%), fatigue (3.7%), and orthostatic effects (3.2%) 6
• Withdrawal rates due to adverse effects are relatively low, with dizziness (0.8%), cough (0.6%), and fatigue (0.4%) being the most common reasons 6
• Electrolyte monitoring is important as the combination can affect potassium levels, though the effect is typically modest 1, 2

Dosing Considerations

• Initial therapy can start with lower doses (e.g., lisinopril 10 mg with hydrochlorothiazide 12.5 mg) and be titrated as needed 1
• The doses of thiazide diuretics used in successful trials were generally equivalent to 25-50 mg of hydrochlorothiazide, though therapy may be initiated at lower doses 1
• Higher doses of hydrochlorothiazide (>50 mg) add little additional antihypertensive efficacy but increase the risk of adverse effects like hypokalemia 1

Potential Pitfalls and Monitoring

• Monitor serum potassium levels, as the combination can lead to either increases or decreases in potassium depending on individual patient factors 1, 2
• Check renal function periodically, as both medications can affect kidney function, especially in patients with pre-existing renal impairment 1
• Monitor for signs of orthostatic hypotension, particularly when initiating therapy or increasing doses 2
• Be aware that the combination may increase serum uric acid levels, though clinical gout is uncommon with appropriate dosing 1, 6

Patient Selection

• This combination is particularly useful for patients who haven't achieved target blood pressure on monotherapy 1
• The European Society of Cardiology guidelines include ACE inhibitor + diuretic combinations as preferred combinations for hypertension management 1
• The combination may be especially beneficial in patients with concomitant heart failure or high cardiovascular risk 1
• Avoid combining with other renin-angiotensin system blockers (such as ARBs or direct renin inhibitors) as this increases risk without additional benefit 1

The lisinopril-hydrochlorothiazide combination represents a rational approach to hypertension management with complementary mechanisms of action and established efficacy and safety profiles.