Does Losartan Cause Increased Urination?
Losartan does not directly cause increased urination as a primary pharmacologic effect, but it can increase uric acid excretion and may indirectly affect urinary patterns through its renal hemodynamic effects. 1, 2
Direct Renal Effects of Losartan
Losartan's primary renal actions involve hemodynamic changes rather than diuretic effects:
Glomerular filtration rate (GFR) and renal plasma flow (RPF) remain essentially unchanged with losartan monotherapy in patients with essential hypertension, with studies showing GFR of 100 ± 19 vs. 96 ± 17 ml/min/1.73 m² before and after treatment. 2
Losartan increases glomerular filtration rate acutely through mechanisms involving kinins, prostaglandins, and nitric oxide, though this does not translate to clinically significant diuresis. 1
Urinary sodium excretion is not significantly modified by losartan alone, with only a trend toward decreased proximal sodium reabsorption (72.9 ± 7.7% vs. 68.1 ± 6.4% of filtered sodium, p = 0.07). 2
Uricosuric Effect (Not Diuretic)
The most notable excretory effect of losartan is on uric acid, not water:
Losartan increases uric acid excretion by 3.9-fold within 1-2 hours and increases fractional clearance of uric acid by 4.3-fold, leading to decreased serum uric acid levels (195 ± 49 vs. 183 ± 43 μM). 2, 3
This uricosuric effect does not increase risk of acute urate nephropathy because losartan simultaneously increases urine pH, thereby decreasing dihydrogen urate (the primary risk factor for crystal formation) despite increased uric acid excretion. 4
When Urinary Symptoms May Occur
Combination with Diuretics
When losartan is combined with thiazide diuretics (as commonly prescribed in doses of 25-100 mg losartan plus hydrochlorothiazide), the diuretic component—not losartan—causes increased urination. 5, 4
Concurrent diuretic use can exacerbate pre-existing bladder conditions and increase urine production, potentially contributing to urinary urgency. 6
Diabetic Patients on Losartan
If a patient taking losartan experiences urinary urgency or frequency, consider alternative explanations:
Diabetic autonomic neuropathy is a common cause of urinary urgency in patients taking losartan for diabetic nephropathy, resulting in detrusor overactivity and urothelial dysfunction. 6
Women with diabetes have a 30-100% increased risk of urinary incontinence, predominantly urge incontinence, which may coincidentally present in patients taking losartan. 6
Men with benign prostatic hyperplasia (BPH) and diabetes experience more severe lower urinary tract symptoms (LUTS), which may also present in patients taking losartan. 6
Clinical Recommendations
Evaluation Approach
Evaluate for diabetic bladder dysfunction in patients with diabetes experiencing urgency using management strategies such as bladder training and potentially antimuscarinic agents. 6
Consider urodynamic testing if initial management is unsuccessful or the diagnosis is unclear, particularly in diabetic patients with LUTS. 6
Monitoring Parameters
Check serum creatinine and potassium within 2-4 weeks after starting or increasing losartan dose, as renal hemodynamic changes can occur. 7, 8
Monitor for volume status changes when losartan is combined with diuretics, as diuretic dose adjustment may be needed to maintain euvolemia. 8
Common Pitfall to Avoid
Do not attribute increased urination to losartan monotherapy without first evaluating for:
- Concurrent diuretic use (the actual cause of diuresis) 5, 4
- Underlying diabetic bladder dysfunction 6
- Benign prostatic hyperplasia in men 6
- Uncontrolled hyperglycemia causing osmotic diuresis
The confusion often arises because losartan is frequently prescribed in combination products containing hydrochlorothiazide, where the thiazide component—not losartan—causes the diuretic effect. 5, 4