Can ciprofloxacin (Cipro) cause hyponatremia?

Ciprofloxacin and Hyponatremia: Clinical Evidence and Recommendations

Yes, ciprofloxacin can cause hyponatremia through syndrome of inappropriate antidiuretic hormone secretion (SIADH), as documented in recent case reports. 1

Mechanism and Evidence

Ciprofloxacin has been identified as a medication that can induce SIADH, leading to hyponatremia. The 2019 American Geriatrics Society Beers Criteria specifically lists ciprofloxacin among medications that should be used with caution due to its potential to cause or exacerbate hyponatremia through SIADH 2. This risk appears to be a class effect among fluoroquinolones.

A 2024 case report documented a 67-year-old male who developed hyponatremia (sodium 129 mmol/L) with symptoms of lethargy, headache, attention deficits, and depressed mood after starting ciprofloxacin for prostatitis. The patient met all criteria for SIADH, and sodium levels normalized (135 mmol/L) within four days of discontinuing ciprofloxacin, with complete resolution of symptoms 1.

Risk Factors and Clinical Presentation

Patients at increased risk for ciprofloxacin-induced hyponatremia include:

• Older adults (>65 years)
• Patients with pre-existing electrolyte abnormalities
• Those with impaired renal function
• Patients taking other medications that can cause hyponatremia

Clinical manifestations depend on the severity and acuity of hyponatremia:

• Mild symptoms: headache, lethargy, attention deficits, depressed mood
• Moderate symptoms: nausea, confusion, weakness
• Severe symptoms: seizures, coma, respiratory arrest (with severe, acute hyponatremia)

Monitoring Recommendations

For patients on ciprofloxacin:

• Monitor serum electrolytes, particularly in high-risk patients
• The British Thoracic Society guidelines recommend routine monitoring of U&Es (urea and electrolytes) intermittently throughout antibiotic treatment with ciprofloxacin 2
• Be vigilant for symptoms of hyponatremia, especially in elderly patients
• Consider more frequent monitoring in patients with cirrhosis or other conditions predisposing to electrolyte abnormalities

Management of Ciprofloxacin-Induced Hyponatremia

If hyponatremia develops:

1. Assess severity and symptoms
2. Consider discontinuation of ciprofloxacin and switch to an alternative antibiotic class
3. For symptomatic hyponatremia:
   • Fluid restriction (1-1.5 L/day) for mild to moderate cases 2
   • Hypertonic saline (3%) for severe symptomatic cases with slow correction 2
   • Monitor serum sodium levels closely during correction

Clinical Implications and Alternatives

When prescribing ciprofloxacin:

• Consider the risk of hyponatremia, especially in vulnerable populations
• Be aware that hyponatremia may develop within days of initiating treatment
• Monitor for early signs of hyponatremia in high-risk patients
• Consider alternative antibiotics if the patient has a history of hyponatremia

Special Populations

In patients with cirrhosis and ascites, ciprofloxacin is used for prophylaxis against spontaneous bacterial peritonitis (SBP) 2, 3. These patients already have dysregulated fluid and electrolyte balance, making them particularly susceptible to hyponatremia. When using ciprofloxacin in this population:

• Monitor electrolytes more frequently
• Consider the risk-benefit ratio carefully
• Be aware that intravenous ciprofloxacin contains significant sodium (30 mmol in 200 ml/400 mg) 2

While the overall incidence of severe adverse effects with ciprofloxacin is relatively low (0.6% in clinical trials) 4, clinicians should remain vigilant about the potential for hyponatremia, especially in vulnerable populations.