Drug Study: Triconex Forte

Generic name: metronidazole
Brand name: Triconex Forte 500 mg tablet
Category: antiprotozoal/ amoebicide

Formulation: each tablet contains: metronidazole 500mg


Pharmacodynamic properties:

Metronidazole is an anti-infective agent belonging to the 5-nitroimidazole group. The antimicrobial spectrum of Metronidazole concerns exclusively anaerobic microorganisms.
Susceptible species: more than 90% are susceptible. Bacteroides sp., Fusobacterium Clostridium sp., C. perfringes, Bacteroides fragilis, Fusobacterium, Peptostreptococcus
The antiparasitic activity concerns: trichomonas vaginalis, Giardia intestinalis, Entamoeba histolytica

Pharmacokinetic properties:
Absorption:
Metronidazole is rapidly absorbed following oral administration, at least 80% in less than one hour. The peak serum concentrations achieved following oral administration are similar to those obtained following intravenous administration of equivalent doses. The oral bioavailability is 100% and is not modified by simultaneous ingestion of food.

Distribution:
Approximately one hour after a single dose administration of 500 mg of Metronidazole, the peak serum concentration is on average 10 mcg/mL. The plasma half-life is between 8 to 10 hours. The protein binding is low: <20%. The volume of distribution is large, on average 40 L (i.e. 0.66L/kg). Diffusion of the drug is rapid and extensive with concentrations close to serum levels in the lungs, kidneys, liver, skin, bile, CSF, saliva, seminal fluid and vaginal secretion. Metronidazole crosses the placenta barrier and is excreted in breast milk.

Metabolism:
Metronidazole is primarily metabolized in the liver. Oxidation yields two main metabolites:
-the alcoholic metabolites, the primary metabolites, with a bactericidal activity against anaerobic bacteria equal to approximately 30% of that of Metronidazole; and with an elimination half-life of 11 hours.
-the acid metabolite, in small amounts, and with bactericidal activity approximately equal to 5% of that of Metronidazole.

Elimination:
High liver and biliary concentration. Low concentration in the colon. Little fecal elimination. Excretion is primarily urinary, shown by the fact that the Metronidazole and its oxidation metabolites excreted in the urine account for approximately 35 to 85% of the administered dose.

Indication:
The indications are based on the anti-parasitic and antibacterial activity, and on the pharmacokinetic characteristics of Metronidazole. They are restricted to infections caused by the microorganism defined above as susceptible to Metronidazole:
Urethritis and vaginitis caused by Trichomonas vaginalis.
-intestinal and hepatic amoebiasis
-Giardia intestinalis (Lambilasis_
-infections caused by anaerobic bacteria
-amoebiasis
-urogenital trichomoniasis
-non-specific vaginalis
-Giardiasis
-curative treatment of medico-surgical infections due to susceptible anaerobic pathogens
-prophylaxis against infections caused susceptible anaerobic pathogens in high risk surgical contents
-conversion from prophylais or curative injectable treatment of infection due to susceptible anaerobic contents.

Metronidazole is also indicated in the treatment of trichomoniasis in both male and female patients when the presence of trichomonas has been demonstrated by wet smear or culture and for sexual partners of those patients who have recurrence of infections. Trichomonal infection is demonstrated for other protozoa including Entamoeba histolytica, giardiasis and liver abscess.

Contraindication:
It should not be administered to patients with active neurological disorders or history of blood dyscrasias, hypothyroidism and hypoadrenalism.

Precaution:
When there is clinical evidence of a trichomonal infection, the sexual partner should be treated, concomitantly to avoid re-infestations. Although no persistent hematologic abnormalities have been reported in clinical studies, total and differential leukocytes counts should be made before and after treatment especially if a second course of therapy is needed. Treatment should be discontinued if ataxia or any symptoms CNS occur. Metronidazole has been shown to be carcinogenic in mice. Unnecessary use of the drug should be reserved for conditions described in the indications.
The use of this drug in the first trimester of pregnancy should be avoided. During the second trimester of pregnancy, its use should be restricted to those patients in whom topical measures have been proven inadequate. Metronidazole is secreted in the breast milk when administered to nursing mothers. Its use should avoided although there is no reported effect to the newborn.

Drug Interactions:
When given with alcohol, Metronidazole may provoke a disulfiram-like reaction in some patients. Concomitant administration of Metronidazole and disulfiram, have caused acute psychoses or confusion. Metronidazole can enhance the anticoagulant effects of Warfarin. Metronidazole is also reported to impair the metabolism of excretion of the following drugs, with the consequent potential for an increased risk of adverse effects: phenytoin, lithium, and fluorouracil.

Adverse effects:
Infrequent and minor adverse effects include metallic taste, furred tongue and dry mouth, gastrointestinal disturbances such as diarrhea, anorexia, vomiting, epigastric distress, constipation, occasional flushing, and headaches, especially with concomitant ingestion with alcohol, dizziness and rarely incoordination and ataxia have been reported. Occasionally patients have complained of numbness or paresthesia of extremities, fleeting joint pains have been experienced, as have confusion, irritability, depression, urticaria, pruritus, dysuria, cystitis, urethral discomfort and darkening of the urine have occurred in patients receiving the drug.

Dosage:
Adult dose to be taken with or after meals, or as prescribed by a physician.
Amoebiasis, Balantidiasis and Blastocystitis hominis infection: 1 tablet three times daily for 5 to 10 days or 3 to 5 tablets as a single dose daily for 2 or 3 days.
Giardiasis: 4 tablets once daily for 3 successive days or 1 tablet twice daily for 7 to 10 days.
Trichomoniasis: 4 tablets once daily or 1 tablet twice daily for 7 days.
Bacterial vaginosis: 4 tablets once daily or 1 tablet twice daily for 5 to 7 days.
Anaerobic bacterial infections: 1 tablet every 8 hours
Prevention of postoperative anaerobic bacterial infections: 1 tablet every 8 hours before surgery followed postoperatively by intravenous or rectal administration until oral therapy is possible.

Cautions: foods, drugs, devices and cosmetics act prohibits dispensing without prescription

Availability: box of 100s; foil strip of 10‘s
Store at temperatures not exceeding 30 degrees Celsius.


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