Chlorthalidone and Lisinopril: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Chlorthalidone
Lisinopril
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Both of these medicines lower your blood pressure, so together they can lower it more than either one alone. Chlorthalidone is a water pill (diuretic) that makes you lose extra fluid and salt. Lisinopril relaxes your blood vessels. When you start lisinopril while already taking a water pill, your pressure can drop quickly, especially with that first dose.
You might feel dizzy or lightheaded, particularly when standing up. The good news is this is usually temporary, and your care team can manage it easily by adjusting your doses and checking on you. Just stand up slowly at first and let your doctor or pharmacist know if you feel faint.
Additive antihypertensive effect. Adding lisinopril (ACE inhibitor) to established chlorthalidone (thiazide-type diuretic) therapy can produce excessive BP reduction and first-dose hypotension.
- Mechanism: ACE inhibitor vasodilation superimposed on diuretic-induced intravascular volume/sodium depletion. Neither agent requires metabolic activation; this is a pharmacodynamic (not PK) interaction.
- Direction: Enhanced hypotensive effect; risk highest with volume depletion.
- Onset: Rapid (first dose). Evidence: Theoretical/well-recognized class effect.
- Management: Consider reducing/holding diuretic or liberalizing salt before initiation; if not feasible, start lisinopril at a lower dose. Monitor BP and orthostatics.
What happens
Reduction of blood pressure
Interaction Deep Dive
For patients already receiving diuretics, starting an ACE inhibitor can produce an excessive drop in blood pressure3. Cases of severe postural hypotension have been documented when an ACE inhibitor is combined with existing diuretic therapy. This effect has more frequently been seen with loop diuretics; however, first dose hypotension occurs commonly among patients who are hypovolemic or sodium depleted as a result of diuretic use or restricted sodium intake. Typically, this hypotensive reaction is transient6271. To reduce the likelihood of these hypotensive effects prior to beginning the ACE inhibitor, one may lower or stop the diuretic or raise salt intake. When such steps cannot be taken, lower the initial dose of the ACE inhibitor3.
Why it happens (mechanism)
Vasodilation and relative intravascular volume depletion
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is used on purpose to control blood pressure, but the first doses need care.
- Your care team may lower or briefly pause the water pill, or have you take in a bit more salt, before starting lisinopril.
- If that is not an option, they may start lisinopril at a lower dose and adjust it, individualized to you.
- Expect closer blood pressure checks early on.
- Stand up slowly, and tell your pharmacist or doctor if you feel dizzy, lightheaded, or faint.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In a randomized crossover trial (N=19) evaluating the simultaneous use of hydrochlorothiazide and enalapril in older patients (62 to 84 years), the pharmacokinetics of enalapril were relatively unaffected by hydrochlorothiazide; however, there was a significant rise in AUC (0 to 24 hours) and a significant decrease in the renal clearance of enalaprilat 4.
b) A small decrease in peak serum concentrations of perindoprilat, along with a reduction in the proportion of the perindopril dose eliminated as perindoprilat in the urine, has been documented when perindopril and hydrochlorothiazide are given together 5.
Common questions
Can I take Chlorthalidone and Lisinopril together?
Starting lisinopril while on chlorthalidone can cause a sharp, usually temporary drop in blood pressure, so watch for dizziness early on and let your care team adjust doses and monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Chlorthalidone and Lisinopril interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Chlorthalidone and Lisinopril interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is used on purpose to control blood pressure, but the first doses need care. Your care team may lower or briefly pause the water pill, or have you take in a bit more salt, before starting lisinopril. If that is not an option, they may start lisinopril at a lower dose and adjust it, individualized… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Chlorthalidone or Lisinopril need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (7)
- Vlasses PH, Ferguson RK, & Chatterjee K: Captopril: clinical pharmacology and benefit-to-risk ratio in hypertension and congestive heart failure. Pharmacotherapy 1982; 2:1-17. PubMed
- Gluck Z, Beretta-Piccoli C, & Reubi FC: Long-term effects of captopril on renal function in hypertensive patients. Eur J Clin Pharmacol 1984; 26:315-323. PubMed
- Product Information: QBRELIS(TM) oral solution, lisinopril oral solution. Silvergate Pharmaceuticals (per manufacturer), Greenwood Village, CO, 2016. DailyMed
- Weisser K, Schloos J, Jakob S, et al: The influence of hydrochlorothiazide on the pharmacokinetics of enalapril in elderly patients. Eur J Clin Pharmacol 1992; 43:173-177. PubMed
- Todd PA & Fitton A: Perindopril: a review of its pharmacological properties and therapeutic use in cardiovascular disorders. Drugs 1991; 42:90-114.
- Atkinson AB, Brown JJ, Morton JJ, et al: Captopril in a hyponatremic hypertensive; need for caution initiating therapy (letter). Lancet 1979; 1:557-558.
- Pandhi P, Mondal S, Sharma BK, et al: Low dose captopril alone and in combination with hydrochlorothiazide in treatment of mild to moderate essential hypertension. Int J Clin Pharmacol Ther Toxicol 1986; 24:294-297.
Keep reading about Chlorthalidone
Keep reading about Lisinopril
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist