Lisinopril and Cyclopenthiazide: 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
Cyclopenthiazide
No brand names on recordLisinopril
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.
Cyclopenthiazide is a water pill (diuretic) and lisinopril is a blood pressure medicine. Both lower blood pressure, so when they are used together, your pressure can drop more than expected, especially with the very first doses of lisinopril. You might feel dizzy, lightheaded, or faint when you stand up quickly.
The good news is this drop is usually temporary and settles as your body adjusts. This combination is used on purpose all the time. Your care team can manage it easily by starting lisinopril at a low dose and watching how you respond. If you feel dizzy, sit or lie down and let your pharmacist or doctor know.
Effect: Additive antihypertensive effect. Thiazide-induced volume/sodium depletion plus ACE inhibitor vasodilation can cause an exaggerated first-dose hypotensive response, including postural hypotension.
Direction/mechanism: Pharmacodynamic (not metabolic); neither agent is enzyme-dependent here. Cyclopenthiazide reduces intravascular volume, potentiating lisinopril-mediated vasodilation.
- Onset: Rapid (first dose)
- Evidence: Theoretical, though first-dose hypotension is well described clinically
- Severity: Moderate; response usually transient
Management: Consider reducing/withholding the diuretic or liberalizing salt before initiation; if not feasible, use a reduced lisinopril starting dose. Monitor BP, especially standing, and volume status.
What happens
Reduction of blood pressure
Interaction Deep Dive
When an ACE inhibitor is started in patients already receiving diuretics, blood pressure may drop excessively3. Cases of severe postural hypotension have been documented after ACE inhibitors are added to diuretic regimens. This complication occurs more frequently with loop diuretics, but first dose hypotension is also common among patients who have sodium depletion or hypovolemia resulting from diuretics or restricted sodium intake. Typically, this hypotensive reaction is transient6271. The risk of hypotensive effects can be reduced by lowering or stopping the diuretic, or by raising salt intake, prior to beginning ACE inhibitor therapy. When such approaches cannot be carried out, the initial dose of the ACE inhibitor should be lowered3.
Why it happens (mechanism)
Vasodilation and relative intravascular volume depletion
How to manage this interaction
This is a common, manageable combination. Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
To lower the risk of your blood pressure dropping too far when lisinopril is started, your care team may:
- Reduce or pause the water pill (cyclopenthiazide) beforehand
- Suggest a bit more salt in your diet, if appropriate
- Start lisinopril at a lower dose and adjust it, individualized to you
- Monitor your blood pressure more closely, including when standing
Stand up slowly, and if you feel dizzy or faint, sit or lie down. Tell your pharmacist or doctor about any lightheadedness so they can fine-tune your doses.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) A randomized crossover trial (N=19) examining the simultaneous use of hydrochlorothiazide and enalapril in elderly patients (aged 62 to 84 years) found that hydrochlorothiazide had relatively little effect on the pharmacokinetics of enalapril, though there was a significant rise in AUC (0 to 24 hours) along with a significant decrease in the renal clearance of enalaprilat 4.
b) A slight decline in peak serum concentrations of perindoprilat, together with a reduction in the proportion of the perindopril dose excreted as perindoprilat in the urine, has been documented when perindopril and hydrochlorothiazide are given together 5.
Common questions
Can I take Lisinopril and Cyclopenthiazide together?
Adding lisinopril to the diuretic cyclopenthiazide can cause an exaggerated, usually temporary drop in blood pressure with early doses; your care team manages this with a low starting dose and closer monitoring. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Lisinopril and Cyclopenthiazide 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 Lisinopril and Cyclopenthiazide interaction managed?
This is a common, manageable combination. Keep taking both exactly as prescribed unless your prescriber tells you otherwise. To lower the risk of your blood pressure dropping too far when lisinopril is started, your care team may: Reduce or pause the water pill (cyclopenthiazide) beforehand Suggest a bit more salt in your diet, if appropriate Start lisinopril at a lower dose and adjust it, individ… 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 Lisinopril or Cyclopenthiazide 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 Cyclopenthiazide
Keep reading about Lisinopril
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