According to the Beers Criteria, what recommendations apply to the use of fluoroquinolones and trimethoprim‑sulfamethoxazole (Bactrim) in adults aged 65 years and older?

Beers Criteria Recommendations for Fluoroquinolones and Bactrim in Older Adults

According to the 2019 AGS Beers Criteria, both fluoroquinolones (specifically ciprofloxacin) and trimethoprim-sulfamethoxazole (Bactrim/TMP-SMX) should be used with significant caution in adults 65 years and older, particularly in those with reduced kidney function, and specific drug-drug interactions must be avoided.

Fluoroquinolones (Ciprofloxacin)

Renal Function Considerations

Ciprofloxacin should be avoided or dose-reduced in older adults with impaired kidney function due to increased risk of CNS effects and tendon rupture 1. This represents a new addition to the 2019 criteria specifically addressing safety concerns in the geriatric population.

Critical Drug-Drug Interactions to Avoid

The 2019 Beers Criteria added several important ciprofloxacin interactions 1:

• With warfarin: Avoid this combination as it increases bleeding risk (macrolides excluding azithromycin have the same concern)
• With theophylline: Avoid due to increased risk of theophylline toxicity

Trimethoprim-Sulfamethoxazole (Bactrim)

Use With Caution Scenarios

TMP-SMX requires careful monitoring in three high-risk situations 1:

1. Patients with reduced kidney function taking ACE inhibitors or ARBs: This combination significantly increases hyperkalemia risk and requires close serum potassium monitoring 2

2. Renal impairment alone: TMP-SMX should be avoided or dose-reduced in patients with creatinine clearance <30 mL/min due to worsening renal function and hyperkalemia risk 1

3. Elderly patients on thiazide diuretics: Increased incidence of thrombocytopenia with purpura has been reported 2

Critical Drug-Drug Interactions to Avoid

The 2019 update added TMP-SMX to the drug-drug interaction table 1:

• With phenytoin: Increases phenytoin toxicity risk; monitor serum phenytoin levels 2
• With warfarin: Increases bleeding risk; monitor prothrombin time and INR closely 2
• With methotrexate: Avoid concurrent use—sulfonamides displace methotrexate from protein binding and compete with renal transport, increasing free methotrexate concentrations 2

Dosing Adjustments for Renal Impairment

Per FDA labeling, specific dose reductions are required 2:

• CrCl >30 mL/min: Standard dosing
• CrCl 15-30 mL/min: Reduce dose by 50%
• CrCl <15 mL/min: Use not recommended

Common Pitfalls to Avoid

1. Failing to check potassium levels: When prescribing TMP-SMX to patients on ACE inhibitors/ARBs, close potassium monitoring is mandatory, not optional 1, 2

2. Ignoring renal function: Both agents require renal dose adjustment, but this is frequently overlooked in older adults who may have normal serum creatinine despite reduced creatinine clearance

3. Overlooking drug interactions: The warfarin interactions with both agents are particularly dangerous given the high prevalence of anticoagulation in older adults

4. Inadequate hydration counseling: Patients must maintain adequate fluid intake to prevent crystalluria and stone formation with TMP-SMX 2

Clinical Context

While the 2019 Beers Criteria emphasizes caution rather than absolute avoidance for these agents, the multiple warnings reflect genuine safety concerns in the geriatric population. The criteria specifically note that these additions were made based on evidence of harm that is either unique to or more pronounced in older adults 1. The 2023 update maintained these recommendations, confirming their ongoing relevance 3.

The key principle: These antibiotics can be used in older adults when clinically indicated, but require heightened vigilance for drug interactions, renal function monitoring, and electrolyte abnormalities—particularly hyperkalemia with TMP-SMX.