What could be causing increased confusion and falls in a geriatric patient with a urinary tract infection (UTI) on day 6 of Bactrim (trimethoprim/sulfamethoxazole)?

Bactrim-Induced Adverse Effects in a Geriatric Patient with UTI

The increased confusion and falls in your geriatric patient are most likely adverse effects of trimethoprim-sulfamethoxazole (Bactrim) treatment, and you should consider discontinuing the medication and evaluating for alternative causes of the patient's symptoms. 1, 2

Drug-Related Causes of Confusion and Falls

• Trimethoprim-sulfamethoxazole can cause neurological adverse effects in elderly patients, including confusion, which may be contributing to your patient's symptoms 2
• A case of toxic delirium has been reported after concomitant intake of sulfamethoxazole/trimethoprim with certain medications that are OCT2 substrates 2
• Elderly patients are particularly susceptible to adverse drug reactions due to age-related changes in pharmacokinetics and pharmacodynamics 3
• Drug interactions may be exacerbating the confusion - Bactrim interacts with many medications commonly prescribed in geriatric patients, including:
  • Diuretics (especially thiazides) - can cause thrombocytopenia and electrolyte disturbances 2
  • Oral hypoglycemics - can potentiate hypoglycemic effects 2
  • Warfarin - can increase anticoagulant effects 2
  • ACE inhibitors - can cause hyperkalemia 2

Distinguishing UTI from Asymptomatic Bacteriuria

• The Infectious Diseases Society of America (IDSA) strongly recommends against treating asymptomatic bacteriuria in older adults with functional or cognitive impairment who experience falls or confusion 3
• Confusion and falls in elderly patients with bacteriuria are often incorrectly attributed to UTI when they may be due to other causes 3, 1
• The relationship between bacteriuria and delirium is likely attributable to underlying host factors rather than a true inflammatory or infection-related association 3
• Studies show that delirious patients treated for asymptomatic bacteriuria had poorer functional outcomes compared to untreated patients 1

Management Algorithm

1. Evaluate for Bactrim adverse effects:

   • Check for other signs of adverse drug reactions (rash, blood dyscrasias, electrolyte abnormalities) 2
   • Review medication list for potential drug interactions with Bactrim 2

2. Consider discontinuing Bactrim if:

   • The patient has completed an adequate course of therapy (typically 3-7 days for uncomplicated UTI) 4
   • The confusion and falls began after starting the medication 1
   • No other clear source of infection is present 3

3. Investigate alternative causes of confusion and falls:

   • Dehydration, electrolyte abnormalities, or other metabolic disturbances 3
   • Other infections (respiratory, skin) 3
   • Medication effects from other drugs 3
   • Environmental changes or sleep disturbances 1

4. If UTI symptoms persist after stopping Bactrim:

   • Consider alternative antibiotics with fewer neurological side effects 4
   • Options include nitrofurantoin, fosfomycin, or pivmecillinam if appropriate for the patient's renal function and pathogen susceptibility 4

Common Pitfalls to Avoid

• Attributing non-specific symptoms like confusion solely to UTI without considering medication adverse effects 1
• Continuing antibiotics when symptoms may be due to the medication itself rather than the infection 3
• Failing to recognize that bacteriuria is common in elderly patients and does not always indicate infection requiring treatment 3
• Overlooking drug interactions that may be contributing to the patient's symptoms 2

Key Monitoring Recommendations

• Monitor mental status after discontinuing Bactrim - improvement would suggest drug-induced delirium 1
• Assess for signs of clinical improvement or deterioration after medication changes 3
• Evaluate for other causes of delirium using a structured approach 3
• Consider checking electrolytes, renal function, and complete blood count to evaluate for other Bactrim-related adverse effects 2