Protozole

METRONIDAZOLE

500 mg Tablet

ANTIBACTERIAL/ANTIPROTOZOAL

Category:

Description

FORMULATION

Each tablet contains:

Metronidazole USP………………………………… 500 mg

PHARMACOLOGICAL ACTION

Metronidazole has anti-protozoal activity and is effective against Trichomonas vaginalis and other protozoal including Entamoeba histolytica and Giardia intestinalis. Metronidazole has bactericidal activity against anaerobic bacteria, including Bacteroides species.

MECHANISM OF ACTION

Metronidazole is a prodrug. Unionized metronidazole is selective for anaerobic bacteria due to their ability to intracellularly reduce metronidazole to its active form. This reduced metronidazole then covalently binds to DNA, disrupt its helical structure, inhibiting bacterial nucleic acid synthesis and resulting in bacterial cell death.

PHARMACOKINETIC PROPERTIES

Metronidazole given orally is well absorbed from the gastrointestinal tract with bioavailability >90% for tablets; Metronidazole is distributed widely in the body and has low protein binding (<20%). The volume of distribution at steady state in adults is 0.51 to 1.1 L/kg. Metronidazole reaches 60 to 100% of plasma concentrations in most tissues studied, including the central nervous system, but does not reach high concentrations in placental tissue.

Metronidazole is extensively metabolized by the liver to 5 metabolites. The hydroxy metabolite has biological activity of 30 to 65% and a longer elimination half-life than the parent compound. The majority of metronidazole and its metabolites are excreted in urine and faeces, with less than 12% excreted unchanged in urine.

The pharmacokinetics of metronidazole are unaffected by acute or chronic renal failure, haemodialysis, continuous ambulatory peritoneal dialysis, age, pregnancy or enteric disease. Renal dysfunction reduces the elimination of metronidazole metabolites; however, no toxicity has been documented and dosage alterations are unnecessary. Liver disease leads to a decreased clearance of metronidazole and dosage reduction is recommended.

INDICATIONS

For the treatment of anaerobic protozoal infections such as amoebiasis (intestinal and extra intestinal) giardiasis/trichomoniasis, balantidiasis, blastocystiasis, and dientamebiasis. For treatment of bacterial infections including Bacteroides fragilis and Clostridium tetani.

CONTRAINDICATIONS

Hypersensitivity to metronidazole. Patients with blood dyscrasias or with active disease of the central nervous system. its use should be avoided during pregnancy.

DOSAGE AND ADMINISTRATION

UROGENITAL TRICHOMONIASIS: where reinfection is likely, the consort should receive a similar course of treatment concurrently for 7 days – one tablet morning and night or for 1 day, five tablets to be taken as a single dose.

AMOEBIASIS:

  1. Intestinal disease in susceptible subjects: 2 tablets three times a day for 5 days or 5 tablets as a single dose for 3 days
  2. Intestinal disease in less susceptible subjects and chronic amoebic hepatitis: 1 tablet three times a day for 5 – 10 days or 5 tablets as a single dose for 2 days
  3. Amoebic liver abscess and also other forms of extra intestinal amoebiasis: 1 tablet three times a day for 5 days or 5 tablets as a single dose for 2 days.

ACUTE ULCERATIVE GINGIVITIS: 1 tablet twice a day for 3 days

GIARDIASIS: A second course of treatment may be necessary for some patients two weeks after the end of the first course for 5 tablets as a single dose for 3 days.

ANAEROBIC INFECTIONS:

  1. Treatment: with other bacteriologically appropriate antibacterial agents for 7 days or longer depending on clinical and bacteriological assessment of the patient’s condition.
    • Adults: 500 mg by mouth three times daily
    • Children and infants: 7 mg/kg body mass by mouth three times daily
  2. Prevention: Adults – 400 mg may be given every 8 hours for 3 – 4 days up to 1 g have been used.

SIDE EFFECTS AND SPECIAL PRECAUTIONS

Peculiar taste in the mouth, furred tongue, nausea, vomiting, gastrointestinal upset, drowsiness, headache, vertigo, ataxia, disorientation, skin rashes and pruritus have been reported.

Alcohol should be avoided during treatment with metronidazole. Slight and transient falls in blood pressure have been reported with the parent substance; it may, therefore be advisable to lower the dosage of any antihypertensive drug which may be given concurrently with the tablets.

During intensive and prolonged treatment bone marrow depression and peripheral neuropathy have been reported. Side effects are more prominent with larger doses.

Metronidazole (PROTOZOLE) enhances the effects of warfarin and if metronidazole is to be given to patients receiving this or other oral anticoagulants, the dosage of the latter should be recalibrated.

OVERDOSAGE AND PARTICULARS OF ITS TREATMENT

In recent overdosage gastric lavage is recommended. Further treatment is symptomatic and supportive.

STORAGE

Store at temperatures not exceeding 30°C.

KEEP ALL MEDICINES OUT OF REACH OF CHILDREN.

AVAILABILITY

Metronidazole (PROTOZOLE) 500 mg TABLET: Alu/PVC Blister Pack x 10’s (Box of 30’s and 100’s)

 

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