Can Bactrim Cause Gait Disorder?
Yes, trimethoprim-sulfamethoxazole (Bactrim) can cause gait disturbances, particularly in elderly patients, those with renal impairment, or patients receiving high doses, though this is an uncommon adverse effect.
Evidence for Gait Disturbance
Case Reports and Clinical Studies
A documented case of higher-level gait disorder (HLGD) occurred in an 82-year-old man receiving high-dose Bactrim (1600 mg/320 mg daily) for pulmonary abscess. The patient developed gait ignition failure, poor balance, and frequent falls by day 40 of therapy, which completely resolved within 3 days of discontinuing the medication 1.
Multiple studies in patients with Machado-Joseph disease demonstrated that Bactrim actually improved gait and coordination, suggesting the drug has neurological effects that can modulate motor function—though paradoxically, this same mechanism may cause adverse gait effects in susceptible individuals 2, 3, 4.
High-Risk Populations
Elderly patients are at substantially increased risk for neurological adverse effects from Bactrim, including gait disturbances 1. The American Geriatrics Society specifically identifies trimethoprim-sulfamethoxazole as requiring caution in older adults, with recommendations for more frequent monitoring 5.
Patients with renal impairment face elevated risk because both trimethoprim and sulfamethoxazole accumulate when creatinine clearance falls below 30 mL/min, potentially leading to neurotoxicity 6. The 2019 AGS Beers Criteria emphasizes particular caution when Bactrim is used in combination with ACE inhibitors or ARBs in patients with reduced kidney function 5.
Mechanism and Clinical Presentation
The gait disorder appears to be a central nervous system effect rather than peripheral neuropathy, manifesting as higher-level gait dysfunction with features including difficulty initiating gait, poor balance, and ataxia 1.
Neuropsychiatric adverse reactions with TMP/SMX are infrequently reported but well-documented, and clinicians should maintain a high index of suspicion, especially in vulnerable populations 1.
Risk factors that increase susceptibility include: advanced age, malnutrition, hepatic dysfunction, renal impairment, and high-dose therapy 1.
Clinical Management Algorithm
When evaluating a patient on Bactrim with new gait disturbance:
Immediately assess renal function and check serum electrolytes (particularly potassium and sodium), as metabolic derangements can contribute to neurological symptoms 5, 6.
Review the dose and duration of therapy. High doses (>800 mg/160 mg twice daily) and prolonged treatment increase risk 1.
Exclude other causes of acute gait disturbance through targeted neurological examination, but do not delay discontinuation if Bactrim is the likely culprit 1.
Discontinue Bactrim if it is the probable cause. Gait typically normalizes within 3-5 days of stopping the medication 1.
Consider alternative antibiotics based on the infection being treated and susceptibility patterns.
Monitoring Recommendations
For elderly patients or those with renal impairment receiving Bactrim, proactively assess gait and balance during therapy, particularly after dose escalations 5, 1.
Monitor renal function and electrolytes at baseline, 1-2 weeks after initiation, and periodically during therapy 5.
Educate patients and caregivers to report new difficulty walking, dizziness, or falls immediately 1.
Important Caveats
While gait disturbance is a recognized adverse effect, it remains uncommon in the general population receiving standard doses. However, the combination of advanced age, renal dysfunction, and high-dose therapy creates a perfect storm for neurotoxicity 1, 6. The reversibility of symptoms upon drug discontinuation supports a direct causal relationship 1.