Last reviewed 2026-04-20 · How we verify

Microzide (hydrochlorothiazide)

Lisinopril inhibits ACE, reducing angiotensin II and aldosterone, leading to lower blood pressure.

Hydrochlorothiazide (Microzide) is a marketed generic diuretic primarily indicated for hypertension, originally developed by Merck. Its key strength lies in its well-established use and broad acceptance in the treatment of hypertension, contributing to its stable market position. The primary risk is the key composition patent expiry in 2028, which could intensify competition from other generics.

At a glance

Mechanism of action

Lisinopril works by blocking the angiotensin-converting enzyme (ACE), which normally converts angiotensin I to angiotensin II, a substance that narrows blood vessels and raises blood pressure. By inhibiting ACE, lisinopril reduces the levels of angiotensin II, leading to dilated blood vessels and lower blood pressure. This also decreases aldosterone secretion, which can slightly increase potassium levels in the blood.

Approved indications

• Hypertension

Boxed warnings

• WARNING: FETAL TOXICITY When pregnancy is detected, discontinue lisinopril and hydrochlorothiazide tablets as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus. See Warnings, Fetal Toxicity .

Common side effects

• dizziness
• headache
• cough
• fatigue
• orthostatic effects
• diarrhea
• nausea
• upper respiratory infection
• muscle cramps
• asthenia
• paresthesia
• hypotension

Drug interactions

• Diuretics
• Non-steroidal Anti-inflammatory Agents (NSAIDs), including selective COX-2 inhibitors
• Angiotensin Receptor Blockers (ARBs), ACE inhibitors, or Direct Renin Inhibitors (e.g., aliskiren)

Key clinical trials

• A Prospective, Non-interventional, Observational, Multi-center Trial to Evaluate Compliance and Efficacy in Mono and Combination Treatment of Candesartan Cilexetil(Atacand)/ Candesartan Cilexetil 16mg (N/A)
• Use of Diuretics in Maintenance Hemodialysis Patients With Residual Renal Function Undergoing Bioimpedance-guided Fluid Management (NA)
• A Randomized, Double-Blind, Placebo-Controlled, 2-Part Study to Evaluate the Multiple Dose Effects of Hydrochlorothiazide and Isosorbide Mononitrate on Glucose Homeostasis in Obese Patients With Hyper (Phase 1)
• An Open Label, Single Arm Prospective Study to Evaluate Efficacy and Safety of Losartan Based Therapy Reslio® (Losartan) and Resilo-h® (Losartan+Hydrochlorthiazide) in Diabetic and Uncontrolled Hypert (Phase 4)
• An Open-label Study to Evaluate the Trough and Peak Effect of Once Daily Micardis Plus (Telmisartan 80mg / Hydrochlorothiazide 12.5 mg) by 24 ABPM in Patients With Mild to Moderate Essential Hypertens (Phase 3)
• A 12-week Multicenter, Randomized, Double-blind, Parallel-group, Active-control Study to Evaluate the Antihypertensive Efficacy and Safety of Valsartan/Amlodipine-based Regimen Versus a Losartan-based (Phase 4)
• A Phase III, Randomized, Active-Comparator Controlled Clinical Trial to Study the Efficacy and Safety of MK-0954E in Japanese Patients With Essential Hypertension Uncontrolled With Losartan and Amlodi (Phase 3)
• Compliance of Patients With Essential Hypertension Treated With Candesartan or Candesartan/Hydrochlorothiazide (N/A)

Patents

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Microzide CI brief — competitive landscape report
• Microzide updates RSS · CI watch RSS
• Generic (originally Merck) portfolio CI