Treating CAP: Which Oral Drug Is Best After Discharge?

Jason E. Bowling, MD


May 06, 2019


As is often the case with CAP, the sputum and blood cultures were negative and therefore of little value when choosing an antibiotic. But the patient's favorable response to the antibiotics he has already received and the recommendations from clinical guidelines indicate that he should complete a course of antibiotics targeting Streptococcus pneumoniae, the most common bacterial pathogen causing CAP. His age (> 65 years old) places him at increased risk for drug-resistant S pneumoniae.[1,2] Taking these facts into account, I would choose amoxicillin, which I believe will best complete his course of therapy with the lowest risk for adverse events.

Either of the respiratory fluoroquinolones, moxifloxacin or levofloxacin, would effectively eradicate S pneumoniae as well as other atypical bacterial pathogens known to cause CAP. Ciprofloxacin is not sufficiently active against S pneumoniae and is generally not recommended for empiric CAP treatment. Both respiratory fluoroquinolones are attractive options because they can be given as monotherapy for CAP, are dosed daily, and are frequently used as step-down oral agents in patients being discharged from the hospital. Unfortunately, they are also burdened by some significant adverse effects and carry US Food and Drug Administration warnings about the risk for tendonitis, tendon rupture, delirium, disorientation, and peripheral neuropathy.[3] Furthermore, this patient's known GERD and intermittent use of antacids prompt a concern for drug-drug interactions and reduced oral bioavailability, because fluoroquinolones are chelated by divalent and trivalent cations found in aluminum- and calcium-containing antacids.

Amoxicillin is effective against S pneumoniae and should be used at higher doses (1 g by mouth three times daily) in light of the patient's age-related elevated risk for drug-resistant S pneumoniae. While any antibiotic can increase the risk for Clostridium difficile colitis, amoxicillin's narrower spectrum of activity makes it a less risky option than a fluoroquinolone. Beta-lactams are generally well tolerated, with a lower risk for serious side effects. Because this patient has already received three doses of azithromycin (1500 mg), covering most atypical bacterial pathogens, amoxicillin alone should be adequate, along with outpatient follow-up, to finish his course of therapy.

Azithromycin and doxycycline monotherapy are less preferred for finishing his course because of their higher risk for antibiotic resistance in comparison with the other choices. Like the fluoroquinolones, doxycycline can interact with coadministered antacids.


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