Does Losartan Cause Urine Retention?
No, losartan does not cause urine retention—in fact, it increases urinary excretion of uric acid and other substances, making urine retention physiologically inconsistent with its mechanism of action.
Mechanism and Urinary Effects
Losartan acts as an angiotensin II receptor antagonist that actually increases urinary excretion rather than causing retention:
- Losartan increases urinary uric acid excretion by 3.9-fold within 1-2 hours of administration, demonstrating enhanced renal excretion rather than retention 1
- The drug increases fractional clearance of uric acid by 4.3-fold and also enhances excretion of oxypurinol and xanthine through common renal transport pathways 2
- Losartan reduces proteinuria by 25-43% in diabetic patients with microalbuminuria, reflecting improved glomerular function rather than obstructive pathology 3, 4
Recognized Adverse Effects (Not Including Retention)
The established adverse effects of angiotensin receptor blockers like losartan are well-documented in guidelines and do not include urinary retention:
Renal Effects
- Worsening renal function can occur due to efferent arteriolar vasodilation, particularly in patients dependent on angiotensin II for glomerular filtration (e.g., bilateral renal artery stenosis, severe heart failure) 5, 6
- A modest 10-20% rise in serum creatinine is expected and hemodynamic in nature, not indicative of obstruction 6
- Monitor creatinine and potassium within 1-2 weeks after initiation or dose changes 6, 7
Hyperkalemia
- Potassium retention (not urine retention) is a recognized adverse effect, occurring especially in patients with chronic kidney disease, diabetes, or those taking potassium-sparing diuretics 5, 6
- Losartan typically increases serum potassium by approximately 1 mEq/L 6
- Halt losartan if potassium rises to ≥6.0 mmol/L 6
Hypotension
- Blood pressure declines are common but symptomatic hypotension requiring intervention is uncommon 5
- Monitor blood pressure in both sitting and standing positions, particularly in elderly patients 7
Clinical Context
Common pitfall: Confusing functional renal insufficiency (reduced GFR from hemodynamic changes) with obstructive uropathy or urine retention. These are entirely different pathophysiologic processes 5, 6.
If a patient on losartan develops urinary symptoms suggesting retention (hesitancy, incomplete emptying, decreased stream), investigate alternative causes such as:
- Prostatic hypertrophy in men
- Anticholinergic medications
- Neurogenic bladder
- Anatomic obstruction
The uricosuric effect of losartan may theoretically increase the frequency of urinary calculi, but this represents stone formation rather than primary urine retention 2.