Metronidazole 500 mg Tablet

Therapeutic Class: Anti-Infectives

Dosage Forms: Tablets

Brand Name: Metronidazole 500 mg Tablet

How it works?

Uses of Metronidazole 500 mg Tablet

What are the Uses of Metronidazole 500 mg tablet?

Anaerobic infections (caused by bacteria that thrive without oxygen), such as:
- Dental infections.
- Skin and soft tissue infections.
- Bone and joint infections.
- Abdominal infections (e.g., peritonitis)

Parasitic Infections

Amebiasis—an intestinal infection caused by Entamoeba histolytica.
Giardiasis—a diarrheal illness caused by Giardia lamblia.

Sexually Transmitted Infections (STIs)

Trichomoniasis—caused by Trichomonas vaginalis, often treated in both partners.

Gynecological Conditions

Bacterial vaginosis—imbalance of vaginal bacteria.
Pelvic inflammatory disease (PID)—often used in combination with other antibiotics.

Gastrointestinal Conditions

Helicobacter pylori infections—part of combination therapy for stomach ulcers.
Clostridium difficile colitis—sometimes used when other treatments aren’t suitable.

Surgical Prophylaxis

Given before surgery to prevent infection, especially in colorectal procedures.

Dosages administration of Metronidazole 500 mg Tablet

Dosage & Administration Guide of Metronidazole 500 mg Tablet

General Administration Instructions

Route: Oral use only
Timing: Take during or after meals
Method: Swallow whole with water; do not chew

Special Populations

Elderly

Use with caution, especially at high doses
Limited data on dosage modification

Hepatic Impairment

In hepatic encephalopathy: → Administer ⅓ of the daily dose once daily.

Anaerobic Infections

Age Group	Dosage	Frequency	Duration
Children >8 weeks to 12 years	20–30 mg/kg/day	Single dose or 7.5 mg/kg every 8 hrs	Usually 7 days
Severe cases	Up to 40 mg/kg/day	—	—
Children <8 weeks	15 mg/kg/day	Single dose or 7.5 mg/kg every 12 hrs	—
Preterm newborns (<40 weeks gestation)	Monitor serum levels	—	—

Children under 10 years: Use a more suitable dosage form.

Prophylaxis (Anaerobic Infection – Surgical Context)

Adults

1 g stat dose 24 hrs pre-op
Then 400 mg every 8 hrs for 24 hrs pre-op
Continue post-op via IV or rectal route until oral intake is possible

Children <12 years

20–30 mg/kg as a single dose 1–2 hrs before surgery

Newborns (<40 weeks gestation)

10 mg/kg as a single dose before surgery

Children under 10 years: Use a more suitable dosage form.

Treatment of Established Infections.

Age Group	Dosage	Frequency
Adults & Children >10 years	800 mg initially	Then 400 mg every 8 hrs
Children <10 years	—	Use a more suitable dosage form

Urogenital Trichomoniasis

Group	Dosage Options
Adults & Adolescents	2000 mg single dose OR 200 mg 3× daily for 7 days OR 400 mg 2× daily for 5–7 days
Children <10 years	40 mg/kg single dose OR 15–30 mg/kg/day in 2–3 doses for 7 days (Max 2000 mg/day)

Treat sexual partners simultaneously to prevent reinfection.

Bacterial Vaginosis

Group	Dosage Options
Adults	400 mg 2× daily for 7 days OR 2000 mg single dose
Adolescents	400 mg 2× daily for 5–7 days OR 2000 mg single dose

Amoebiasis

Age Group	Dosage	Frequency	Duration
Adults over 10 years	400–800 mg	3× daily	5–10 days
Children 7–10 years	200–400 mg	3× daily	5–10 days
Children 3–7 years	100–200 mg	4× daily	5–10 days
Children 1–3 years	100–200 mg	3× daily	5–10 days
Alternative (All ages)	35–50 mg/kg/day	3 divided doses	Max 2400 mg/day

Children under 7 years: Use a more suitable dosage form.

Giardiasis

Age Group	Dosage Options
Adults >10 years	2000 mg once daily for 3 days OR 400 mg 3× daily for 5 days OR 500 mg 2× daily for 7–10 days
Children 7–10 years	1000 mg once daily for 3 days
Children 3–7 years	600–800 mg once daily for 3 days
Children 1–3 years	500 mg once daily for 3 days
Alternative	15–40 mg/kg/day	Divided in 2–3 doses

Children under 7 years: Use a more suitable dosage form.

Dental & Skin Infections

Condition	Age Group	Dosage	Duration
Acute Ulcerative Gingivitis	Adults & Children >10 years	200 mg 3× daily	3 days
Acute Dental Infections	Adults & Children >10 years	200 mg 3× daily	3–7 days
Leg Ulcers/Pressure Sores	Adults & Children >10 years	400 mg 3× daily	7 days

Children under 10 years: Use a more suitable dosage form.

Helicobacter pylori (Combination Therapy)

20 mg/kg/day.
Max dose: 500 mg twice daily.
Duration: 7–14 days.
Follow official guidelines before initiating therapy.

Side effects of Metronidazole 500 mg Tablet

Side Effects of Metronidazole 500 mg Tablet

Alcohol: Avoid alcohol during treatment and for 48 hours after stopping metronidazole. It may cause flushing, low blood pressure, and other serious reactions.
Porphyria: Use with caution.
Blood & CNS Conditions: Do not use in patients with blood disorders or active non-infectious brain diseases.
Syphilis: High doses may mask symptoms—ensure proper testing.
Seizure Risk: Use cautiously in patients with epilepsy or seizure history.
Pregnancy: Use with caution in the 2nd and 3rd trimesters for vaginal infections.
Long-Term Use: If treatment exceeds 10 days, regular clinical and lab monitoring is advised.
Peripheral Neuropathy: Weigh benefits vs. risks in chronic use.
Trichomoniasis: Gonorrhea may persist even after Trichomonas is treated—follow-up testing may be needed.
Renal Impairment:
- No dose adjustment is needed, but metabolites may accumulate.
- Hemodialysis: Re-administer metronidazole immediately after dialysis.
- Peritoneal Dialysis (IPD/CAPD): No dose adjustment required.
Liver Impairment:
- In hepatic encephalopathy, reduce the dose to one-third, given once daily.
- In Cockayne syndrome, metronidazole should only be used if no alternatives exist. Liver function tests are mandatory before, during, and after treatment. Discontinue if liver values worsen.
Skin Reactions: Discontinue immediately if signs of SJS, TEN, or AGEP appear.
Urine Discoloration: May darken urine—this is harmless.
Mutagenicity Risk: Long-term use should be avoided unless absolutely necessary.

Precautions of Metronidazole 500 mg Tablet

Precautions When Using Metronidazole 500 mg Tablet

Alcohol

Do not drink alcohol during treatment and for 48 hours after stopping metronidazole. It can cause serious reactions like flushing and low blood pressure.

Health Conditions

Porphyria: Use with caution.
Blood disorders or brain conditions (not caused by infection): Avoid using metronidazole.
Epilepsy or history of seizures: High doses may trigger seizures—use carefully.
Syphilis: High doses may hide signs of syphilis—testing is important.

Pregnancy & Breastfeeding

Pregnancy:
- Not safe in the first trimester.
- Use with caution in the second and third trimesters for vaginal infections.
- For other uses, only take if absolutely necessary and no safer option is available.
Breastfeeding:
- Stop breastfeeding during treatment and for 12–24 hours after stopping the medicine.

Monitoring

If treatment lasts more than 10 days, regular check-ups and lab tests are recommended.
Long-term use may cause nerve damage—weigh the benefits and risks carefully.

Infections

Even after treating Trichomonas vaginalis, other infections like gonorrhea may still be present—follow-up testing may be needed.

Kidney Function

Kidney failure: No dose change needed, but the body may hold onto drug by-products. The effect of this is unclear.
Hemodialysis: The drug is removed during dialysis—take a dose right after dialysis.
Peritoneal dialysis (IPD or CAPD): No dose adjustment needed.

Liver Function

Liver disease or encephalopathy: Use with caution. Reduce the dose to one-third and take once daily.
Cockayne syndrome:
- Serious liver damage has occurred, sometimes fatal.
- Only use if absolutely necessary and no other treatment is available.
- Liver tests must be done before, during, and after treatment.
- Stop treatment if liver tests worsen.
- Report any signs of liver problems (like yellowing of skin or eyes) immediately.

Skin Reactions

Rare but serious skin conditions like SJS, TEN, or AGEP have been reported.
Stop the medicine immediately if you notice a rash, blisters, or peeling skin.

Other Notes

Metronidazole may darken urine—this is harmless.
Long-term use should be avoided unless absolutely necessary due to unclear risks related to genetic changes.

Storage instruction of Metronidazole 500 mg Tablet

Store below 30°C.

Keep out of reach of children.

Packing details of Metronidazole 500 mg Tablet

6×3 Alu/PVC Blister

Metronidazole 500 mg tablets are available in an Alu/PVC blister of 6 tablets. Such 3 blisters in a unit carton with a package insert.

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