Your EMR may offer you a “helpful” allergy warning when ordering a carbapenem because your patient is allergic to penicillins or cephalosporins; the cross reactivity is very low and most people tolerate carbapenems with a low risk of allergic reaction.
Add anti-MRSA only for a real risk factor — it is not routine in CAP. Risks: prior MRSA (infection, colonization, or positive nasal PCR); hospitalization or IV antibiotics ≤90 days; severe, necrotizing, or cavitary pneumonia; empyema; recent influenza; ESRD/dialysis; injection drug use. Negative nasal PCR (NPV ~95–99%) → reasonable to withhold or stop.
VancomycinMRSA
???
Monitor: target AUC/MIC 400–600; check a level before the 4th dose.
Scope: soft-tissue infection without evidence of osteomyelitis. Probe-to-bone or exposed bone suggests osteomyelitis — treat as osteomyelitis (different workup and a longer course).
Ceftriaxone₃500 mg IM once if <150 kg body weight 1 gm IM once if >150 kg body weight
Doxycycline100 mg PO q12h for 7 days
Ceftriaxone₃ AND AzithromycinFor pregnant patients
★
Ceftriaxone₃500 mg IM once if <150 kg body weight 1 gm IM once if >150 kg body weight
Azithromycin1 gm PO once
OR
500 mg on day 1, followed by 250 mg once daily for the next 4 days (Z-Pak)
Gentamicin AND AzithromycinFor cephalosporin allergic patients
Gentamicin240 mg IM once
Azithromycin2 gm PO once
Cefixime₃ AND DoxycyclineOnly if ceftriaxone administration is not available or not feasible; higher risk of treatment failure for pharyngeal infections
Cefixime₃800 mg PO once
Doxycycline100 mg PO q12h for 7 days
Cefixime₃ AND AzithromycinOnly if ceftriaxone administration is not available or not feasible; higher risk of treatment failure for pharyngeal infections
Cefixime₃800 mg PO once
Azithromycin1 gm PO once
OR
500 mg on day 1, followed by 250 mg once daily for the next 4 days (Z-Pak)