Antibiotics by diagnosis

Initial antimicrobial therapy for acutely ill

Hospitalized adults pending identification of causative organism

Suspected Clinical Diagnosis	Likely Etiologic Diagnosis	Drugs of Choice
Meningitis, bacterial, community-acquired6	Pneumococcus1, meningococcus	Cefotaxime2, 2–3 g IV every 6 hours; or ceftriaxone, 2 g IV every 12 hours plus vancomycin, 10 mg/kg IV every 8 hours
Meningitis, bacterial, age > 50, community-acquired6	Pneumococcus, meningococcus, Listeria monocytogenes3, gram-negative bacilli	Ampicillin, 2 g IV every 4 hours, plus Cefotaxime or ceftriaxone and vancomycin
Meningitis, postoperative (or posttraumatic)6	S aureus, gram-negative bacilli (pneumococcus, in posttraumatic)	Vancomycin, 10 mg/kg IV every 8 hours, plus ceftazidime, 3 g IV every 8 hours
Brain abscess	Mixed anaerobes, pneumococci, streptococci	Penicillin G, 4 million units IV every 4 hours, plus metronidazole, 500 mg orally every 8 hours; or Cefotaxime or ceftriaxone plus metronidazole, 500 mg orally every 8 hours
Pneumonia, acute, community-acquired, severe	Pneumococci, M pneumoniae, 'Legionella', C pneumoniae	Doxycycline, 100 mg IV or orally every 12 hours (or azithromycin), plus Cefotaxime, 2 g IV every 8 hours (or ceftriaxone, 1 g IV every 24 hours); or a fluoroquinolone5 alone
Pneumonia, postoperative or nosocomial	S aureus, mixed anaerobes, gram-negative bacilli	Cefapime, 2 g IV every 8 hours; or , 2 g IV every 8 hours; or piperacillin-tazobactam, 45 g IV every 6 hours; or imipenem, 500 mg IV every 6 hours; or meropenem, 1 g IV every 8 hours plus tobramycin, 5 mg/kg IV every 24 hours; or ciprofloxacin, 400 mg IV every 12 hours; or levofloxacin, 500 mg IV every 24 hours plus vancomycin, 15 mg/kg IV every 12 hours
Endocarditis, acute (including injection drug user)	S aureus, E faecalis, gram-negative aerobic bacteria, viridans streptococci	vancomycin, 15 mg/kg IV every 12 hours, plus gentamicin, 1 mg/kg every 8 hours
Septic thrombophlebitis (eg, IV tubing, IV shunts)	S aureus, gram-negative aerobic bacteria	Vancomycin, 15 mg/kg IV every 12 hours plus ciprofloxacin, 400 mg IV every 12 hours; or levofloxacin, 500 mg IV every 24 hours; or ceftriaxone, 1 g IV every 24 hours
Osteomyelitis	S aureus	Nafcillin, 2 g IV every 4 hours; or cefazolin, 2 g IV every 8 hours
Septic arthritis	S aureus, N gonorrhoeae	Ceftriaxone , 1–2 g IV every 24 hours
Pyelonephritis with flank pain and fever (recurrent urinary tract infection)	E coli, Klebsiella, Enterobacter, Pseudomonas	Ceftriaxone, 1g IV every 24 hours; or ciprofloxacin, 400 mg IV every 12 hours (500 mg orally); or levofloxacin, 500 mg once daily (IV/PO)
Fever in neutropenic patient receiving cancer chemotherapy	S aureus, Pseudomonas, Klebsiella, E coli	Ceftazidime, 2 g IV every 8 hours; or cefepime, 2 g IV every 8 hours
Intra-abdominal sepsis (eg, postoperative, peritonitis, cholecystitis)	Gram-negative bacteria, Bacteroides, anaerobic bacteria, streptococci, clostridia	Piperacillin-tazobactam or ticarcillin-clavulanate, 3.1 g IV every 6 hours; or ertapenem, 1 g every 24 hours; or moxifloxacin, 400 mg IV every 24 hours

¹Some strains may be resistant to penicillin. Vancomycin can be used with or without rifampin.

²Cefotaxime, ceftriaxone, ceftazidime, or ceftizoxime can be used. Most studies on meningitis have been with cefotaxime or ceftriaxone (see text).

³TMP-SMZ can be used to treat Listeria monocytogenes in patients allergic to penicillin in a dosage of 15–20 mg/kg of TMP in three or four divided doses.

⁴Depending on local drug susceptibility pattern, use tobramycin, 5 mg/kg/d, or amikacin, 15 mg/kg/d, in place of gentamicin.

⁵Gatifloxacin, levofloxacin, moxifloxacin

⁶Remember to give steroids concomitatntly or 15 minutes prior to antibiotics for acute bacterial meningitis

Antibiotics By Diagnosis

Diagnosis	Commonly Used Antibiotic(s)
Meningitis	Vancomycin 750mg (15mg/kg) IV PLUS Ceftriaxone 2g (50mg/kg) IV ADD Ampicillin 2g (50mg/kg) IV if concern for Listeria
Otitis Media	Amoxicillin 500mg (45mg/kg) PO Q12 OR Augmentin 500mg (45mg/kg) PO Q12 OR Cefdinir 600mg (14mg/kg) PO Daily
Otitis Externa	Ciprodex 3gtt Q12 OR Polysporin otic 5gtt Q6
Pharyngitis	Bicillin 1.2 million units (25k/kg) IM OR Azithromycin 500mg (12mg/kg) PO Daily
Corneal Abrasion	Erythromycin ophthalmic Q6 OR Levofloxacin 0.5% 2gtt Q2 if patient is a contact user
Orbital Cellulitis	Vancomycin 1g (15mg/kg) IV Q12
Appendicitis	Zosyn 4.5g (100 mg/kg) IV Q6 OR Flagyl 500mg (7.5mg/kg) IV Q6 PLUS Ciprofloxacin 400mg IV Q12
Cholecystitis	Augmentin 3g IV Q6 OR Imipenem/Cilastin 500mg IV Q6
Diverticulitis	Flagyl 500mg PO Q6 PLUS Ciprofloxacin 750mg PO Q12
Infectious Diarrhea	Empiric: Cipro 500mg PO Q12 x3d Giardia: Flagyl 500mg PO Q8 x5d C. diff: Flagyl 500mg PO Q8 x14d
Epididymitis	Age <35 (gonorrhea suspected): Doxycycline 100mg PO Q12 x14d PLUS Cefixime 400mg PO once Age >35 (gonorrhea not suspected): Ciprofloxacin 500mg PO Q12 x14d
Cervicitis/Urethritis	Cefixime 400mg PO once OR Azithromycin 1g PO once ADD Flagyl 2g PO once if concern for trichomoniasis
PID	Ceftriaxone 250mg 1M once PLUS Doxycycline 100 mg PO Q12 x14d
UTI	Macrobid 100mg PO BID x7d OR Bactrim DS PO Q12 x3d OR Keflex 500mg PO Q6 x7d
Pneumonia	Outpatient: Azithromycin 500mg PO, 250mg PO x3d OR Doxycycline 100mg PO Q12 x7d Inpatient, Community Acquired Ceftriaxone 1g IV PLUS Azithromycin 500mg IV Inpatient, Health Care Acquired Vancomycin 1g IV (MRSA) PLUS Cefepime 2g IV (Pseudomonas) PLUS Tobramycin 4mg/kg IV (Pseudomonas)
Cellulitis/Superficial Abscess	Bactrim DS 2tab PO Q12 x5-10d PLUS Cephalexin 500mg PO Q6 x5-10 OR Clindamycin 450mg PO Q8 x5-10d Diabetic with systemic toxicity Vancomycin 1g IV PLUS Unasyn 3g IV OR Zosyn 3.375g IV
Neutropenic Fever	Zosyn 4.5g IV OR Meropenem 1g IV PLUS/MINUS Gentamicin 2mg/kg IV ADD Vancomycin 1g IV for catheter related infection, colonization with MRSA, gram-positive culture unknown susceptibility, suspected sepsis

See Also

• Antibiotics (Main)
• Initial Antibiotics in Sepsis

Source

• CURRENT Medical Dx & Tx
• University of Cincinnati Department of Emergency Medicine "Handbook of EM Fundamentals"