From the Guidelines
For this 73-year-old man with a UTI, culture showing sensitivity to ampicillin or nitrofurantoin (Macrobid), and a creatinine clearance of 64 mL/min, I recommend nitrofurantoin (Macrobid) 100 mg twice daily for 5-7 days. This is an appropriate first-line option given his renal function is adequate (above the threshold of 30 mL/min required for nitrofurantoin) 1. Nitrofurantoin achieves high concentrations in the urinary tract and has a lower risk of collateral damage to gut flora compared to ampicillin. According to the guidelines, ampicillin should not be used for empirical treatment given the relatively poor efficacy and high prevalence of antimicrobial resistance to these agents worldwide 1.
Key Considerations
- Nitrofurantoin has a high clinical cure rate of 93% and a bacterial cure rate of 88% 1
- The patient's renal function is adequate for nitrofurantoin use, with a creatinine clearance of 64 mL/min
- Amoxicillin or ampicillin should not be used for empirical treatment due to poor efficacy and high resistance rates 1
- Nitrofurantoin is effective for lower UTIs, concentrating in the bladder and making it an excellent choice for uncomplicated urinary tract infections in patients with adequate renal function
Treatment Recommendations
- Nitrofurantoin (Macrobid) 100 mg twice daily for 5-7 days
- Increase fluid intake during treatment
- Take nitrofurantoin with food to minimize gastrointestinal side effects
- Complete the full course of antibiotics even if symptoms improve before completion
- Seek medical attention if symptoms worsen or do not improve within 48-72 hours 1
From the FDA Drug Label
In patients with renal function impairment, ampicillin-class antibiotics can be removed by hemodialysis but not by peritoneal dialysis. The patient's CRCl is 64, which indicates mild renal impairment.
- The dose of ampicillin may need to be adjusted in patients with renal impairment. However, the label does not provide specific dosing recommendations for patients with a CRCl of 64. Given the lack of direct information, no conclusion can be drawn about the specific dosing of ampicillin for this patient 2.
From the Research
Treatment Options for UTI
- The patient is a 73-year-old man with a UTI, and the culture shows susceptibility to ampicillin or Macrobid (nitrofurantoin) 3, 4.
- Considering the patient's age and renal function (CRCl 64), nitrofurantoin may be a suitable option, as it is commonly used to treat uncomplicated lower urinary tract infections in older adults 5, 6.
- However, it is essential to consider the potential for long-term side effects of nitrofurantoin, especially in elderly patients 3.
Antibiotic Resistance and Allergy
- The study by 7 highlights the impact of antibiotic allergy and resistance on antibiotic selection for recurrent UTIs in older women.
- The results show that many older women with RUTIs are allergic or resistant to common antibiotics, including trimethoprim-sulfamethoxazole, fluoroquinolones, and nitrofurantoin.
- In some cases, nitrofurantoin may be the only viable alternative due to allergy and/or antibiotic resistance 7.
Considerations for Treatment
- When selecting an antibiotic, it is crucial to consider the patient's renal function, as some antibiotics may require dose adjustment or be contraindicated in patients with impaired renal function 4.
- The patient's age and potential for long-term side effects should also be taken into account when choosing an antibiotic 3.
- The Infectious Diseases Society of America guidelines recommend nitrofurantoin, trimethoprim-sulfamethoxazole, and Fosfomycin as first-line antibiotic treatments for uncomplicated UTIs 5.