Should a patient with elevated blood pressure (hypertension) who is currently taking lisinopril (angiotensin-converting enzyme inhibitor) 20mg daily, but not hydrochlorothiazide (HCTZ) (thiazide diuretic) 25mg, start taking the prescribed HCTZ?

Management of Elevated Blood Pressure in a Patient Not Taking Prescribed HCTZ

The patient should start taking the prescribed hydrochlorothiazide (HCTZ) 25mg along with the lisinopril 20mg daily to achieve better blood pressure control. 1

Assessment of Current Situation

• Current BP: 160/80 mmHg (Stage 2 Hypertension)
• Current medication: Lisinopril 20mg daily only
• Missing medication: HCTZ 25mg (not being taken as prescribed)

Rationale for Adding HCTZ

1. Combination therapy is recommended:

   • The 2020 International Society of Hypertension guidelines recommend a combination of an ACE inhibitor/ARB with a thiazide diuretic as standard treatment for hypertension in non-black patients 2
   • The patient's current BP of 160/80 mmHg is not controlled on lisinopril monotherapy

2. Evidence for combination effectiveness:

   • Adding HCTZ to lisinopril provides superior blood pressure reduction compared to increasing the lisinopril dose alone 3
   • The combination of lisinopril and HCTZ has demonstrated greater BP reduction than either component alone 4

3. FDA-approved approach:

   • The FDA label for lisinopril specifically states: "If blood pressure is not controlled with lisinopril tablets alone, a low dose of a diuretic may be added (e.g., hydrochlorothiazide, 12.5 mg)" 5

Implementation Plan

1. Start HCTZ immediately:

   • Begin the prescribed HCTZ 25mg daily along with the current lisinopril 20mg
   • This combination will provide better 24-hour blood pressure control 3

2. Monitoring after adding HCTZ:

   • Check blood pressure in 2-4 weeks to assess effectiveness 1
   • Check electrolytes, particularly potassium, within 2-4 weeks of adding HCTZ 1
   • Target blood pressure should be 120-129 mmHg systolic 2

3. Potential adjustments:

   • If BP remains uncontrolled after adding HCTZ, consider adding a dihydropyridine calcium channel blocker as the next step 1
   • If BP drops too much or patient experiences side effects, consider reducing HCTZ dose to 12.5mg 5

Important Considerations

• Medication adherence: Emphasize the importance of taking both medications as prescribed
• Single-pill combination: Consider switching to a fixed-dose single-pill combination of lisinopril and HCTZ to improve adherence if available 2
• Potential side effects of HCTZ: Monitor for electrolyte disturbances, particularly hypokalemia
• Lifestyle modifications: Reinforce dietary approaches (DASH diet, sodium restriction), regular physical activity, weight management, and limited alcohol consumption 1

Pitfalls to Avoid

• Don't increase lisinopril dose alone: Adding HCTZ is more effective than simply increasing the lisinopril dose for patients with uncontrolled BP 3
• Don't add another RAS blocker: Combining two RAS blockers (such as adding an ARB to lisinopril) is explicitly contraindicated 2, 1
• Don't delay treatment: Prompt initiation of the combination therapy is recommended for confirmed BP ≥140/90 mmHg to reduce cardiovascular risk 2

By adding the prescribed HCTZ 25mg to the current lisinopril regimen, you can expect a significant improvement in blood pressure control with a good safety profile.