Losartan Overdose: Potential Complications
The most likely manifestations of losartan overdose are hypotension and tachycardia, with bradycardia possible from parasympathetic stimulation; neither losartan nor its active metabolite can be removed by hemodialysis. 1
Primary Cardiovascular Complications
Hypotension (Most Common)
- Profound hypotension is the hallmark complication of losartan overdose, resulting from excessive angiotensin II receptor blockade and loss of compensatory vasoconstriction 1
- The hypotension may be refractory to standard vasopressor therapy, particularly when combined with other antihypertensive agents 2
- Symptomatic hypotension manifests as dizziness, lightheadedness, or syncope 1
Heart Rate Abnormalities
- Tachycardia typically occurs as a compensatory response to hypotension 1
- Bradycardia can develop from parasympathetic (vagal) stimulation, representing a paradoxical response 1
Renal Complications
Acute Kidney Injury
- Worsening renal function or acute renal failure can occur, particularly in patients with pre-existing kidney disease, volume depletion, or bilateral renal artery stenosis 1, 3
- The mechanism involves loss of angiotensin II-mediated efferent arteriolar vasoconstriction, reducing glomerular filtration pressure 4
- Clinical manifestations include oliguria, rising serum creatinine, and fluid retention (swelling of feet, ankles, hands, or unexplained weight gain) 1
- This complication is typically reversible upon discontinuation of the drug 4, 3
Electrolyte Disturbances
Hyperkalemia
- Elevated serum potassium represents a serious complication, especially in patients with renal impairment or those taking potassium supplements, potassium-sparing diuretics, or NSAIDs 1
- Risk is amplified in overdose situations where renal function may be compromised 1
Less Common but Serious Complications
Allergic Reactions
- Angioedema involving swelling of face, lips, throat, or tongue can occur, though extremely rare (reported in only 3 patients among millions treated) 1, 5
- This requires immediate discontinuation and emergency medical intervention 1
Hepatotoxicity
- Severe hepatic injury has been reported in rare cases, though causality remains uncertain 6, 7, 5
- One case demonstrated markedly elevated liver enzymes following losartan use 6
- Hepatic injury typically occurs during the initial treatment phase if it develops 7
Pancreatitis
- Delayed-onset acute pancreatitis has been documented in at least one case report occurring nearly a week after losartan overdose 8
Management Considerations
Treatment Approach
- Supportive care is the mainstay of treatment for losartan overdose 1
- For hypotension: fluid resuscitation with crystalloids and colloids should be initiated first 2
- Standard vasopressors (epinephrine, norepinephrine, phenylephrine) may be required for refractory hypotension 2
- High-dose insulin euglycemia (HIE) therapy has shown benefit in severe cases, particularly when combined with calcium channel blocker co-ingestion 2
- Hemodialysis is ineffective as neither losartan nor its active metabolite are dialyzable 1
Monitoring Requirements
- Continuous hemodynamic monitoring for blood pressure and heart rate 1
- Serial assessment of renal function (serum creatinine, urine output) 4, 1
- Serum potassium levels, particularly in high-risk patients 1
- Evaluation for volume status and signs of fluid retention 1
Important Clinical Caveats
- Co-ingestion with other antihypertensives (particularly calcium channel blockers) can produce profound, refractory toxicity requiring aggressive multimodal therapy 2, 9
- Elderly patients and those with pre-existing renal disease are at higher risk for complications 3
- The reversible nature of most complications upon drug discontinuation is reassuring, though supportive care may be prolonged 4, 1
- Limited human overdose data exists, with most evidence derived from therapeutic use adverse events and animal studies showing lethality at 44-170 times the maximum human dose 1