Hydrochlorothiazide and Constipation
Hydrochlorothiazide is documented as a constipating medication, though this is not one of its most common side effects. 1
Evidence for Constipation Risk
The clearest evidence comes from a 2012 outbreak investigation where hydrochlorothiazide was specifically identified as a "constipating diuretic medication" in the context of a patient who developed severe complications from Clostridium perfringens infection. 1 This case report explicitly categorizes hydrochlorothiazide alongside other medications with anticholinergic effects that impair gastrointestinal motility, noting that such medications delay the usual elimination of intestinal contents and can prolong exposure to toxins. 1
Mechanism and Clinical Context
While hydrochlorothiazide's primary mechanism involves sodium and water excretion in the distal convoluted tubule, 1 its constipating effect appears related to:
- Electrolyte disturbances: Thiazides commonly cause hypokalemia, which can impair intestinal smooth muscle function 1
- Fluid depletion: Volume depletion from diuresis may reduce intestinal fluid content 1
- Indirect motility effects: The medication can contribute to slowed gastrointestinal transit 1
Common vs. Rare Side Effects
It is important to note that constipation is not listed among the most frequently reported side effects of hydrochlorothiazide. 2 The most common adverse effects are typically:
- Dizziness, weakness, and fatigue (related to fluid and electrolyte imbalances) 2
- Hypokalemia 1
- Hyperuricemia 1
- Metabolic disturbances (hyperglycemia, mild cholesterol changes) 1
Clinical Implications
Patients taking hydrochlorothiazide who develop constipation should be evaluated for:
- Serum potassium levels, as hypokalemia is common with thiazide therapy and can worsen constipation 1
- Concurrent medications with anticholinergic or constipating effects 1
- Adequate hydration status 1
If constipation develops, consider:
- Potassium supplementation or addition of a potassium-sparing diuretic like amiloride if hypokalemia is present 1
- Ensuring adequate fluid intake 1
- Standard constipation management with osmotic laxatives (polyethylene glycol) or stimulant laxatives if needed 3
Important Caveat
The constipating effect of hydrochlorothiazide appears most clinically significant in vulnerable populations, particularly those already taking other medications that impair intestinal motility (such as antipsychotics with anticholinergic properties). 1 In such patients, the combination can create a particularly high risk for severe constipation and its complications.