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Metronidazole Flagyl ® - Renal Dosing

Usual Dosing (Adults)

IV:
Treatment of Anaerobic Infections
The recommended dosage schedule for adults is:
Loading Dose: 15 mg/kg infused over one hour (approximately 1 g for a 70-kg adult).
Maintenance Dose: 7.5 mg/kg infused over one hour every six hours (approximately 500 mg for a 70-kg adult). The first maintenance dose should be instituted six hours following the initiation of the loading dose.

Parenteral therapy may be changed to oral metronidazole when conditions warrant, based upon the severity of the disease and the response of the patient to Metronidazole Injection, USP RTU treatment. The usual adult oral dosage is 7.5 mg/kg every six hours.

A maximum of 4 g should not be exceeded during a 24-hour period.

Patients with severe hepatic disease metabolize metronidazole slowly, with resultant accumulation of metronidazole and its metabolites in the plasma. Accordingly, for such patients, doses below those usually recommended should be administered cautiously. Close monitoring of plasma metronidazole levels3 and toxicity is recommended.

In patients receiving Metronidazole Injection, USP RTU in whom gastric secretions are continuously removed by nasogastric aspiration, sufficient metronidazole may be removed in the aspirate to cause a reduction in serum levels.

The dose of Metronidazole Injection, USP RTU should not be specifically reduced in anuric patients since accumulated metabolites may be rapidly removed by dialysis.

The usual duration of therapy is 7 to 10 days; however, infections of the bone and joint, lower respiratory tract and endocardium may require longer treatment.

Prophylaxis
For surgical prophylactic use, to prevent postoperative infection in contaminated or potentially contaminated colorectal surgery, the recommended dosage schedule for adults is:
15 mg/kg infused over 30 to 60 minutes and completed approximately one hour before surgery; followed by  7.5 mg/kg infused over 30 to 60 minutes at 6 and 12 hours after the initial dose.

It is important that (1) administration of the initial preoperative dose be completed approximately one hour before surgery so that adequate drug levels are present in the serum and tissues at the time of initial incision, and (2) Metronidazole Injection, USP RTU be administered, if necessary, at 6-hour intervals to maintain effective drug levels. Prophylactic use of Metronidazole Injection, USP RTU should be limited to the day of surgery only, following the above guidelines.


Oral:
In elderly patients, the pharmacokinetics of metronidazole may be altered, and, therefore, monitoring of serum levels may be necessary to adjust the metronidazole dosage accordingly.

Trichomoniasis
In the Female
One-day treatment - two grams of FLAGYL, given either as a single dose or in two divided doses of one gram each, given in the same day.

Seven-day course of treatment - 250 mg three times daily for seven consecutive days. There is some indication from controlled comparative studies that cure rates as determined by vaginal smears and signs and symptoms, may be higher after a seven-day course of treatment than after a one-day treatment regimen.

The dosage regimen should be individualized. Single-dose treatment can assure compliance, especially if administered under supervision, in those patients who cannot be relied on to continue the seven-day regimen. A seven-day course of treatment may minimize reinfection by protecting the patient long enough for the sexual contacts to obtain appropriate treatment. Furthermore, some patients may tolerate one treatment regimen better than the other.

Pregnant patients should not be treated during the first trimester. In pregnant patients for whom alternative treatment has been inadequate, the one-day course of therapy should not be used, as it results in higher serum levels which can reach the fetal circulation.

When repeat courses of the drug are required, it is recommended that an interval of four to six weeks elapse between courses and that the presence of the trichomonad be reconfirmed by appropriate laboratory measures. Total and differential leukocyte counts should be made before and after re-treatment.

In the Male
Treatment should be individualized as it is for the female.

Amebiasis
Adults
For acute intestinal amebiasis (acute amebic dysentery): 750 mg orally three times daily for 5 to 10 days.

For amebic liver abscess: 500 mg or 750 mg orally three times daily for 5 to 10 days.

Pediatric patients
35 to 50 mg/kg/24 hours, divided into three doses, orally for 10 days.


Anaerobic Bacterial Infections
In the treatment of most serious anaerobic infections, FLAGYL I.V. (metronidazole hydrochloride) or FLAGYL I.V. RTU® (metronidazole) is usually administered initially.

The usual adult oral dosage is 7.5 mg/kg every six hours (approx. 500 mg for a 70-kg adult). A maximum of 4 g should not be exceeded during a 24-hour period.

The usual duration of therapy is 7 to 10 days; however, infections of the bone and joint, lower respiratory tract, and endocardium may require longer treatment.

Patients with severe hepatic disease metabolize metronidazole slowly, with resultant accumulation of metronidazole and its metabolites in the plasma. Accordingly, for such patients, doses below those usually recommended should be administered cautiously. Close monitoring of plasma metronidazole levels and toxicity is recommended.

The dose of FLAGYL should not be specifically reduced in anuric patients since accumulated metabolites may be rapidly removed by dialysis.

Renal Dosing

dialysis [CRCL > 10]: no changes.



[<10 ml/min  and not on dialysis]
Variable recommendations:
[1] Some sources recommend no changes regardless of the degree of renal insufficiency.  [Package insert]: The dose of Metronidazole Injection, should not be specifically reduced in anuric patients since accumulated metabolites may be rapidly removed by dialysis. Decreased renal function does not alter the single-dose pharmacokinetics of metronidazole.


[2] 50% of usual dose at same interval.  Alternatively: 500mg q12h.

Summary: based on comments from the manufacturer and a quick overview of the clinical pharmacokinetics of metronidazole, dosage reduction or interval extension appears to be unnecessary in patients with renal insufficiency.

Hemodialysis

dialysis Hemodialysis:  On dialysis days, schedule conventional dose after dialysis.   Metronidazole is extensively removed by hemodialysis.

Continuous arteriovenous or venovenous hemofiltration: Dose as for normal renal function.

Reference(s)

National Institutes of Health, U.S. National Library of Medicine, DailyMed Database.
Provides access to the latest drug monographs submitted to the Food and Drug Administration (FDA). Please review the latest applicable package insert for additional information and possible updates.  A local search option of this data can be found here.

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