Metronidazole

General

• Type: Other Antibacterials
• Dosage Forms:
  • IV
  • PO: 250mg; 375mg; 500mg
• Common Trade Names: Flagyl

Adult Dosing

General

• PO
  • 500mg PO q6-8h x 7-10 days
  • First Dose: 500mg PO x 1
• IV
  • 15mg/kg IV x1, then 7.5mg/kg IV q6h
  • First Dose: 15mg/kg IV x1
• Max: 1 gram/dose

Amebic Liver Abscess

• 500-750mg PO q8h x 5-10 days

Colorectal Surgery Infection Prophylaxis

• 15mg/kg IV x 1
• Complete infusion 1h prior to surgery, then 7.5mg/kg IV q6h x 2
• Max: 1 g/dose

Intestinal Amebiasis

• 750mg PO q8h x 5-10 days

PID

• 500mg PO q12 x 14 days
• See PID for full regimen

Bacterial Vaginosis

• Treatment
  • 500mg PO q12 x 7 days
  • Alt: May use 250mg PO q8h x 7 days in pregnant patients
• Prophylaxis (Sexual Assault)
  • 2 g PO x 1

Trichomoniasis

• Treatment
  • Immunocompetent: 2 g PO x 1
  • Immunocompromised: 500mg PO q12h x 7 days
• Prophylaxis (Sexual Assault)
  • 2 g PO x 1

Giardiasis

• 250mg PO q8h x 5-7 days
• Alt: 2 g PO q 24h x 3 days

C. Difficile

• Mild-mod
  • 500mg PO q8h x 10-14 days
• Severe
  • 500mg IV q8h (give with vancomycin PO)

H. pylori

• 250-375mg PO q6h x 10-14 days (in combination)

Urethritis, recurrent/persistent (Non-Gonococcal)

• 2 g PO x 1 (with azithromycin)

Tetanus

• 500 mg IV every 6 hours

Pediatric Dosing

(<1200g)

• 7.5 mg/kg PO/IV q48h
• First Dose: 7.5 mg/kg PO/IV x 1

(>1200g AND <1 Month Old)

• <7 days old
  • 7.5-15 mg/kg/day PO/IV q12-24h
  • First Dose: 7.5-15 mg/kg PO/IV x 1
• >7 days old
  • 15-30 mg/kg/day PO/IV q12h
  • First Dose: 7.5-15 mg/kg PO/IV x 1

(>1 Month Old)

• 30 mg/kg/day PO/IV q6h
• First Dose: 7.5 mg/kg PO/IV x 1
• Max: 4 g/day

Bacterial Vaginosis

<45kg

• 15 mg/kg/day PO divided q12h x 7 days
• First Dose: 7 mg/kg PO x 1
• Max: 1 g/day

>45kg

• 500mg PO divided q8h x 7 days
• First Dose: 500mg PO x 1
• Max: 2 g/day

Prophylaxis (sexual Assault)

<45kg'

• 15 mg/kg/day PO divided q8h x 7 days
• First Dose: 7 mg/kg PO x 1

>45kg

• 2 g PO x 1

Tetanus

Same as Standard Pediatric Age/Weight Dosing

Special Populations

• Pregnancy: B
• Lactation: Safety conditional
• Renal Dosing
  • Adult
    • No adjustment for renal insufficiency
    • Hemodialysis: Give dose after dialysis
    • Peritoneal Dialysis: No supplement
  • Pediatric
    • CrCl <10: Decrease dose 50%
    • Hemodialysis: Give dose after dialysis
    • Peritoneal Dialysis: No supplement
• Hepatic Dosing (Adult & Pediatric)
  • Severe impairment: decrease dose, amount not defined

Contraindications

• Black Box: carcinogenic in mice and rats; avoid unnecessary use; reserved for approved conditions
• Allergy to class/drug
• Pregnancy (single 2 dose retimen)
• Alcohol use within 3 days
• Disulfram use within 14 days

Adverse Reactions

Serious

• Seizures
• Aseptic meningitis
• Perifpheral neuropathy
• Optic neuropathy
• Encephalopathy
• Hypersensitivity Reaction
• Stevens-Johnson Syndrome
• Toxic Epidermal Necrolysis
• Leukopenia
• Carcinogenicity (in animals)

Common

• Disulfiram effect
• Nausea and Vomiting
• Epigastric discomfort
• Diarrhea
• Metallic taste
• Rash
• Headache
• Dizziness
• Dark reddish-brown urine
• Candidiasis
• Thrombophlebitis (IV use)

Pharmacology

• Half-life: 8h
• Metabolism: Liver; CYP450: 2C9 inhibitor
• Excretion: Urine (70%); feces (15%)
• Mechanism of Action: Bactericidal

Antibiotic Sensitivities

Group	Organism	Sensitivity
Gram Positive	Strep. Group A, B, C, G	R
	Strep. Pneumoniae	R
	Viridans strep	X1
	Strep. anginosus gp	X1
	Enterococcus faecalis	R
	Enterococcus faecium	R
	MSSA	R
	MRSA	R
	CA-MRSA	R
	Staph. Epidermidis	R
	C. jeikeium	R
	L. monocytogenes	R
Gram Negatives	N. gonorrhoeae	R
	N. meningitidis	R
	Moraxella catarrhalis	R
	H. influenzae	R
	E. coli	R
	Klebsiella sp	R
	E. coli/Klebsiella ESBL+	R
	E coli/Klebsiella KPC+	R
	Enterobacter sp, AmpC neg	R
	Enterobacter sp, AmpC pos	R
	Serratia sp	X1
	Serratia marcescens	R
	Salmonella sp	R
	Shigella sp	R
	Proteus mirabilis	X1
	Proteus vulgaris	R
	Providencia sp.	X1
	Morganella sp.	X1
	Citrobacter freundii	X1
	Citrobacter diversus	X1
	Citrobacter sp.	X1
	Aeromonas sp	X1
	Acinetobacter sp.	R
	Pseudomonas aeruginosa	R
	Burkholderia cepacia	R
	Stenotrophomonas maltophilia	R
	Yersinia enterocolitica	R
	Francisella tularensis	R
	Brucella sp.	R
	Legionella sp.	R
	Pasteurella multocida	X1
	Haemophilus ducreyi	R
	Vibrio vulnificus	R
Misc	Chlamydophila sp	R
	Mycoplasm pneumoniae	R
	Rickettsia sp	R
	Mycobacterium avium	R
Anaerobes	Actinomyces	R
	Bacteroides fragilis	S
	Prevotella melaninogenica	S
	Clostridium difficile	S
	Clostridium (not difficile)	S+'
	Fusobacterium necrophorum	S
	Peptostreptococcus sp.	I

Key

• S susceptible/sensitive (usually)
• I intermediate (variably susceptible/resistant)
• R resistant (or not effective clinically)
• S+ synergistic with cell wall antibiotics
• U sensitive for UTI only (non systemic infection)
• X1 no data
• X2 active in vitro, but not used clinically
• X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
• X4 active in vitro, but not clinically effective for strep pneumonia

See Also

• Antibiotics (Main)

References

Authors

Ross Donaldson