Is Constipation a Side Effect of Losartan?

Yes, constipation can occur with losartan, although it appears to be relatively uncommon. Constipation is listed among gastrointestinal adverse reactions reported with losartan (brand name Cozaar). ^[1] It is also reported in the combination product losartan/hydrochlorothiazide (brand name Hyzaar). ^{[2] [3]}

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What Official Labeling Says

• Losartan (Cozaar): Constipation is included among gastrointestinal side effects such as abdominal pain, nausea, and vomiting in patient-focused and professional labeling for losartan. ^{[4] [5] [1] [6]}
• Losartan/Hydrochlorothiazide (Hyzaar): Constipation is likewise noted among digestive adverse effects in Hyzaar labeling. ^{[2] [3]}

These listings indicate that constipation has been observed in people taking losartan, either alone or in combination with hydrochlorothiazide. The labels catalog events reported during use, with or without proven causality, and some sections identify events judged related to losartan. ^{[1] [2]}

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How Common Is It?

The detailed clinical trial tables in losartan’s labeling provide frequencies for some gastrointestinal events (like diarrhea and dyspepsia), but they do not give a specific percentage for constipation. ^{[7] [8] [9] [10]} When adverse events lack a listed percentage, it generally suggests they were reported but not among the most frequent events in trials.

• In pooled double‑blind trials of roughly 3,700 participants, losartan’s overall adverse event incidence was similar to placebo, with dizziness being the only commonly reported drug‑related event more frequent than placebo. ^[11] This pattern implies constipation, while possible, is likely infrequent compared with common effects like dizziness. ^[11]

In practical terms, constipation with losartan is recognized but appears to be uncommon or not prominent in clinical trial frequency tables. ^{[7] [11]}

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Possible Contributors and Context

• Drug combination effects: Hyzaar includes hydrochlorothiazide, a diuretic that can sometimes contribute to dehydration; dehydration can make constipation more likely, which may be relevant when losartan is taken with a diuretic. ^{[2] [3]}
• Individual variability: Gastrointestinal responses vary widely; some individuals may experience constipation even when overall trial data show low reporting. ^{[4] [11]}

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Practical Tips If You Suspect Constipation

• Hydration and fiber: Ensuring adequate fluids and dietary fiber can help keep stools soft and bowel movements regular. (General advice; no citation required)
• Activity and routine: Gentle physical activity and regular bathroom routines may reduce constipation. (General advice; no citation required)
• Medication review: If constipation persists, discuss with a clinician whether other medicines (including diuretics or supplements like iron) might be contributing. ^{[2] [3]}
• When to seek care: If constipation is severe, lasts more than a few days, or is accompanied by abdominal pain, vomiting, or blood in stool, medical evaluation is advisable. (General advice; no citation required)

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Summary Table

Below is a concise comparison from official labeling and trial insights:

Item	Losartan (Cozaar)	Losartan/HCTZ (Hyzaar)	Notes
Constipation listed	Yes (gastrointestinal adverse reaction) [1] [4] [5]	Yes (gastrointestinal adverse reaction) [2] [3]	Recognized in both products
Frequency given in trial tables	Not specifically quantified [7] [9] [10]	Not specifically quantified [2] [3]	Absence of % suggests infrequent reporting
Overall AE profile vs placebo	Similar to placebo; dizziness slightly more common with losartan [11]	Combination includes diuretic, which may influence GI symptoms [2] [3]	Constipation likely uncommon in trials

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Bottom Line

Constipation is a recognized but seemingly uncommon side effect of losartan and losartan/hydrochlorothiazide. ^{[1] [2]} Clinical trial summaries do not provide specific frequency percentages for constipation, and overall adverse event rates were comparable to placebo. ^{[7] [11]} If you notice ongoing constipation after starting losartan, it could be related, but many cases can be managed with hydration, fiber, and routine adjustments; consult your clinician if symptoms persist or are severe. ^{[4] [2]}