Metronidazole / Flagyl

(metronidazole)

Brands

Flagyl

Availability

Tablets: 250 mg, 500 mg
Capsules: 375 mg
Injectable: 5 mg/mL

Brand

Metrogyl

Availability

Tablets: 200 mg, 400 mg
Suspension: 200 mg/5mL in 30 mL or 60 mL bottles

Pharmacology

Metronidazole is both a powerful bactericidal agent with activity against most anaerobic bacteria (bacteria that does not require the presence of oxygen to grow), and an amebicide with effective activity against Entamoeba histolytica, Trichomonas, Giardia and Balantidium coli.

The drug is rapidly absorbed and widely distributed from the gastrointestinal tract. It is found in most body tissues, including bone, abscesses, CNS, as well as crossing the placental barrier. Metronidazole is metabolized in the liver and excreted in milk, feces, and urine, coloring the urine dark brown.

It is recommended to avoid use in pregnant and lactating animals, unless benefit outweighs risk.

Indications

Used in bone infections, infections of the tooth socket and abscesses where anaerobic bacteria are likely to be present, and in other enteric and systemic anaerobic infections.

Drug Interactions or Contraindications

Contraindicated in rats where neurological disorders are present.
Not recommended for nursing or pregnant animals.
Avoid concurrent use with phenobarbital, and cimetidine.
It is compatible with all but the following drugs:
- aztreonam
- cefamandole nafate (second generation cephalosporin antibiotic)
- dopamine hcl

Adverse Reactions

CNS: lethargy, weakness, poor coordination

Blood: transient neutopenia, leukopenia

Endocrine: hypoglycemia, hypocalcemia

GI: anorexia, diarrhea, stomatitis

GU: darkened or red-brown urine, cystitis, polyuria, dysuria

Skin: pruritus (itching)

Other: hepatotoxicity

Dosage Recommendations

10 mg to 40 mg/animal (rat), PO, q24hr ²^, ²⁶^, ³⁴^, ³⁵

or

10 mg/kg to 40 mg/kg, PO. Give twice 5 days apart when treating for protozoa. ³⁵

or

10 mg/kg to 50 mg/kg, q12hr ¹¹

or

20 mg/kg to 40 mg/kg, PO, q24hr (rats) ⁴¹^, ⁴² ⁴⁴

or

50 mg/kg to 60 mg/kg, PO, q12hr for 5 days ⁴¹^, ⁴⁴

Considerations

Give with food to avoid GI distress.
In treating suspected polymicrobial infections, where a broader coverage may be needed, synergistic or combination drugs may be used. The following drugs may be seen used simultaneously with metronidazole: aminoglycosides (e.g., amikacin or gentamicin), fluoroquinolones (e.g., enrofloxacin or orbifloxicin), chloramphenicol. ¹, ⁴¹
Tablets and powder for injection should be stored at less than 30 degrees and protected from light.