Metronidazole

These indications are based on manufacturer information for both originator and generic products. For product specific registered indications, please refer to product specific manufacturer information

Registered South African indications: 

• Urogenital trichomoniasis
• Amoebiasis (except carrier state)
• Giardiasis
• Acute ulcerative gingivitis (Vincent's infection)
• Anaerobic bacterial infections
• Prevention of postoperative abdominal and pelvic infections due to anaerobic bacteria:
  - before and after gynaecological surgery
  - before and after appendicectomy
  - before and after colonic surgery

Contraindications

• Hypersensitivity to the active ingredient or any of its excipients
• Hypersensitivity to nitroimidazoles and/or hydroxybenzoates

Cautions

• Pregnancy
• Breastfeeding
• Severe hepatic impairment
• Elderly
• Hepatic encephalopathy
• Acute porphyria
• Administration with any substrate for alcohol dehydrogenase in children <5 years (sus)
• Prolonged use of >10 days
• High-dose treatment
• Active or chronic severe peripheral or central nervous system disorders
  - Fixed or progressive paraesthesia
  - Epilepsy
  - Active disease of the central nervous system (except for brain abscess)
• Cockayne syndrome
• Gonococcal infections after trichomonas vaginalis infection has been eliminated
• Evidence or history of blood dyscrasia
• Alcohol consumption before, during and up to 72 hours after taking metronidazole
• Galactose intolerance (tab)
• Lapp lactase deficiency (tab)
• Glucose-galactose malabsorption (tab, sus)
• Other agents containing sorbitol or fructose (sus)
• Hereditary fructose intolerance (sus)
• Sucrase-isomaltose insufficiency (sus)
• Sodium controlled diet (inj)
• May impair ability to drive and operate machinery

Forms avail. in SA and covered in this monograph: tab, cap, sus, inj

Dosages below include:

• South African Standard Treatment Guidelines indications and dosages
• South African registered indications and dosages
• Indications and dosages registered in other jurisdictions

Infections caused by: Anaerobic organisms (including B. fragilis, F. necrophorum, Prevotella sp., C. difficile, Clostridium sp., Bacteroides sp., Fusobacteria, Clostridia, Eubacteria, anaerobic cocci, Gardnerella vaginalis, Trichomonas vaginalis, Other species of trichomonads Balantidium coli, Entamoeba histolytica, Giardia lamblia, causative organisms of acute ulcerative gingivitis)

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

South African Standard Treatment Guidelines indications and dosages

Pelvic inflammatory disease - stage I (Additional agents required)
- Including those with severe penicillin allergy

• Oral (tab): 400mg, 12hrly; Treatment duration: 7 days
  (STG, Adult 2019)

Pelvic inflammatory disease - stage II-IV (Additional agents required)
- IV therapy prior to switching to oral amoxicillin/ clavulanic acid

• IV: 500mg, 8hrly; Continue until definite clinical improvement usually within 24-48hrs, then switch to oral 
  (STG, Adult 2019)

Peptic ulcer disease (Additional agents required)
- For Helicobacter pylori eradication if H. pylori positive

• Oral (tab): 400mg, 12hrly; Treatment duration: 14 days
  (STG, Adult 2019)

Amoebic liver abscess 
Amoebic dysentery 

• Oral (tab): 800mg, 8hrly; Treatment duration: 10 days
  (STG, Adult 2019)

Clostridium difficile diarrhoea - mild to moderate
- Laboratory confirmed toxigenic Clostridium difficile infection with diarrhoea that does not settle on antibiotic withdrawal

• Oral (tab): 400mg, 8hrly; Treatment duration: 10 days
  (STG, Adult 2019)

Fulminant Clostridium difficile diarrhoea (Additional agent required)
- If ileus or toxic megacolon or hypotension/shock

• IV: 500mg, 8hrly. Treatment duration: 10 days, with switch to oral, if possible, to complete 10 day course 
  (STG, Adult 2019)

Giardiasis

• Oral (tab): 2g, dly; Treatment duration: 3 days
  (STG, Adult 2019; PHC 2020)

Post-exposure prophylaxis, rape and sexual assault (Additional agents required)
- Sexually transmitted infections prophylaxis

• Oral (tab): 2g, immediately as a single dose
  (STG, Adult 2019; Adult 2023; PHC 2020)

Vaginal discharge syndrome (Additional agent required)
- If metronidazole, oral was not given at PHC prior to referral
- Severe penicillin allergy

• Oral (tab): 2g, as a single dose
  (STG, Adult 2019; PHC 2020)

Treatment of a new episode of more than one sexually transmitted infection (STI) syndrome (Additional agents required)
- Vaginal discharge syndrome + genital ulcer syndrome 

• Oral (tab): 2g, immediately as a single dose

- Lower abdominal pain + genital ulcer syndrome

• Oral (tab): 400mg, 12hrly; Treatment duration: 7 days
  (STG, PHC 2020)

Treatment of symptomatic and asymptomatic partners for STIs (Additional agents required)
- Vaginal discharge syndrome 
- Lower abdominal pain 

• Oral (tab): 2g, immediately as a single dose
  (STG, PHC 2020)

Pre-labour rupture of membranes (PROM) at term, prolonged >12hrs/ suspected chorio-amnionitis (Additional agent required)
- Initiate antibiotic therapy
- Severe penicillin allergy

• Oral (tab): 400mg, as a single dose (and refer)
  (STG, PHC 2023)

Brain abscess (Additional agent required)
- Empiric therapy

• Oral (tab): 400mg, 8hrly adjusted according to antimicrobial sensitivity after surgical drainage (and refer) 

OR

• IV: 500mg, 8hrly adjusted according to antimicrobial sensitivity after surgical drainage (and refer)
  (STG, Adult 2019)

Surgical wound infections (Additional agent required)
- Female uro-genital tract surgery or open GIT surgery

• IV: 500mg, 8hrly: Treatment duration: ≤7 days 
  (STG, Adult 2019)

Puerperal sepsis (Additional agent required)

• Oral (tab): 400mg, as a single dose (and refer) 
  (STG, PHC 2023)

Tetanus

• IV: 500mg, 8hrly; Treatment duration: 10 days
  (STG, Adult 2019)

Surgical antibiotic prophylaxis (Additional agent required)

• IV: 500mg, within 1hr before 1st incision; Repeat dose if procedure longer than 8hrs
  (STG, Adult 2019)

Dental abscess (Additional agent required)
- Initiate treatment before referral
Necrotising periodontitis (Additional agent required)
- Initiate treatment before transferral
Human bites (Additional agent required)
- Severe penicillin allergy
Animal bites (Additional agent required) 
- Severe penicillin allergy

• Oral (tab): 400mg, 8hrly; Treatment duration: 5 days
  (STG, PHC 2020; PHC 2023)

Miscarriage (Additional agent required)
- If unsafe (septic) miscarriage is suspected

• Oral (tab): 400mg, as a single dose (before referral)
  (STG, PHC 2023)

---

South African registered indications and dosages

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Treatment of infections caused by or suspected to be caused by anaerobic bacteria, including Bacteroides fragilis, Bacteroides sp, Fusobacteria, Eubacteria, Clostridia and anaerobic streptococci (additional agents required)

• IV: 500mg by infusion, 8hrly, at an infusion rate of 25mg/min; Treatment duration: 7 days
• Oral (tab): Initial: 800mg; Then: 400mg, 8hrly; Treatment duration: 7 days
• Oral (cap): 400mg, 8hrly; Treatment duration: ≥7 days

---

Oral metronidazole at 400mg, 8hrly should be substituted as soon as feasible when administering IV

---

Treatment duration depends on clinical and bacteriological assessments

---

Trichomoniasis 

• Oral (tab): 2g, as a single dose

OR

• Oral (tab): 200mg, 8hrly; Treatment duration: 7 days
• Oral (cap): 200mg, 8hrly: Treatment duration: 7-10 days

OR

• Oral (tab): 400mg, 12hrly; Treatment duration: 7 days

---

If there is no response, a second course of treatment may be given for 7 days after an interval of 4-6 weeks. The white blood cell count should be monitored

---

Sexual partners should be treated concomitantly

---

To be taken after food

---

Hepatitis - acute and chronic
Intestinal amoebiasis 

• Oral (tab, cap): 2-2.4g as a single dose, dly; Treatment duration: 2-3 consecutive days

OR

• Oral (tab, cap): 400-800mg, 8hrly; Treatment duration: 5-10 days

Giardiasis

• Oral (tab, cap): 2g, as a single dose, dly; Treatment duration: 3 days

OR

• Oral (tab): 250mg, 8hrly; Treatment duration: 5-7 days

Vincent's disease (acute necrotising ulcerative gingivitis) 

• Oral (tab, cap): 200mg, 8hrly; Treatment duration: 3 days

OR

• Oral (tab, cap): 400mg, 12hrly; Treatment duration: 3 days

Prevention of postoperative abdominal and pelvic infections due to anaerobic bacteria
- Given before and after gynaecological surgery
- Given before and after appendicectomy
- Given before and after colonic surgery 

• IV: 500mg by infusion, immediately before, during or after an operation; Repeat 8hrly until oral medication can be given (see below)
• Oral (tab, sus): 200-400mg, 8hrly

---

Indications and dosages registered in other jurisdictions

General dosing range for treatment of established anaerobic infection

• Oral (tab, sus): Initial: 800mg; Then: 400mg, 8hrly; Treatment duration: 7 days
• IV: 1-1.5g as a single dose

OR

• IV: 500mg, 8hrly; Treatment duration: 7 days

---

Treatment duration depends on clinical and bacteriological assessments

---

IV route is to be used initially if patients symptoms preclude oral therapy

---

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Urogenital trichomoniasis

• IV/Oral (tab, sus): 2g, as a single dose; Treatment duration: 7 days

OR

• IV/Oral (tab, sus): 200mg, 8hrly; Treatment duration: 7 days

OR 

• IV/Oral (tab, sus): 400mg, 12hrly; Treatment duration: 7 days

- Partner treatment where infection is likely

• Oral (tab, sus): 2g, as a single dose

OR

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 5-7 days

OR 

• Oral (tab, sus): 400mg, 12hrly; Treatment duration: 5-7 days

Bacterial vaginosis

• IV/Oral (tab, sus): 400mg, 12hrly; Treatment duration: 5-7 days

OR 

• IV/Oral (tab, sus): 2g, as a single dose

Amoebiasis

• IV: 400-800mg, 8hrly; Treatment duration: 5-10 days

- Invasive intestinal disease in susceptible subjects

• Oral (tab, sus): 800mg, 8hrly; Treatment duration: 5 days

- Intestinal disease in less susceptible subjects and chronic amoebic hepatitis

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5-10 days

- Amoebic liver abscess
- Other forms of extra-intestinal amoebiasis

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5 days

- Symptomless cyst passers

• Oral (tab, sus): 400-800mg, 8hrly; Treatment duration: 5-10 days

---

Doses may alternatively be expressed by body weight:

---

Oral (tab, sus): 35-50mg/kg in 3 divided doses; Treatment duration: 5-10 days; Max: 2.4mg/24hrs

---

Giardiasis

• IV/Oral (tab, sus): 2g, as a single dose, dly; Treatment duration: 3 days

OR

• IV/Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5 days

OR

• IV/Oral (tab, sus): 500mg, 12hrly; Treatment duration: 7-10 days

---

Doses may alternatively be expressed by body weight:

---

Oral (tab, sus): 15-40mg/kg/day, in 2-3 doses

---

Acute ulcerative gingivitis

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 3 days

Acute dental infections

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 3-7 days

Leg ulcers and pressure sores

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 7 days

Prophylaxis against anaerobic infection
- Chiefly in the context of abdominal (especially colorectal) and gynaecological surgery

• Oral (tab, sus): 400mg, 8hrly during 24hrs immediately preceding operation; Followed by postoperative intravenous or rectal administration until patient is able to take oral medication
• IV: 1-1.5g as a single dose, administered 30-60mins preoperatively

OR

• IV: 500mg administered immediately before, during or after operation; Then: 500mg, 8hrly

Paed. forms avail. in SA and covered in this monograph: tab, cap, sus, inj

Paed. dosages below include:

• South African Standard Treatment Guidelines indications and dosages
• South African registered indications and dosages
• Indications and dosages registered in other jurisdictions

Infections caused by: Anaerobic organisms (including B. fragilis, F. necrophorum, Prevotella sp., C. difficile, Clostridium sp., Bacteroides sp., Fusobacteria, Clostridia, Eubacteria, anaerobic cocci, Gardnerella vaginalis, Trichomonas vaginalis, Other species of trichomonads, Balantidium coli, Entamoeba histolytica, Giardia lamblia, causative organisms of acute ulcerative gingivitis)

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

South African Standard Treatment Guidelines indications and dosages

Peptic ulcer disease (Additional agents required)
- If Helicobacter pylori positive 

• Oral (sus, tab): 7.5mg/kg, 12hrly; Treatment duration: 14 days
  (STG, Paed. 2017)

Acute diarrhoea
- Entamoeba histolytica (if demonstrated on stool microscopy or strongly suspected)
Amoebiasis (Entamoeba histolytica)

• Oral (sus, tab): 15mg/kg/dose, 8hrly; Treatment duration: 7 days; Severe disease: Treatment duration: 10 days 
  (STG, Paed. 2017)

Persistent diarrhoea
-  If Giardia lambia is not excluded

• Oral (sus, tab): 7.5mg/kg/dose, 8hrly; Treatment duration: 5 days
  (STG, Paed. 2017)

- Confirmed Giardia lambia

• Oral (sus, tab): 7.5mg/kg/dose, 8hrly; Treatment duration: 5-7 days
  (STG, Paed. 2017)

Dysentery
- Entamoeba histolytica (if demonstrated on stool microscopy or strongly suspected)

• Oral (sus, tab): 15mg/kg/dose, 8hrly; Treatment duration: 7 days

Surgical antibiotic prophylaxis (Additional agent required)

• IV: 7.5mg/kg, within 1hr before 1st incision; Repeat dose if procedure longer than 8hrs; Max dose: 500mg
  (STG, Paed. 2023)

Tetanus (Additional agents required)
- For hypoxia

• IV: 7.5mg/kg/dose, 8hrly; Treatment duration: 10 days
  (STG, Paed. 2017)

Septicaemia of the newborn
- Anaerobic infections (where anaerobic infection is likely, e.g. after gastro-intestinal surgery for sepsis, or where intra-abdominal sepsis is suspected)

Younger than 4 weeks

• Loading dose: IV: 15mg/kg, given over 60min
• Maintenance dose: IV/Oral (tab, sus): 7.5mg/kg, 12hrly; Treatment duration: 10 days

Older than 4 weeks

• Loading dose: IV: 15mg/kg, given over 60min
• Maintenance dose: IV/ Oral (tab, sus): 7.5mg/kg, 8hrly; Treatment duration: 10 days
  (STG, Paed. 2017)

Necrotising enterocolitis (Additional agents required)
- Empiric antibiotic therapy

Younger than 4 weeks

• Loading dose: IV: 15mg/kg, given over 60min
• Maintenance dose: IV: 7.5mg/kg/dose, 12hrly; Treatment duration: 7 days

Older than 4 weeks

• Loading dose: IV: 15mg/kg, given over 60min
• Maintenance dose: IV: 7.5mg/kg/dose, 8hrly; Treatment duration: 7 days
  (STG, Paed. 2017)

Dental abscess (Additional agent required)
- Initiate treatment before referral
Necrotising periodontitis (Additional agents required)
- Initiate treatment before transferral
Human bites (Additional agent required)
- Severe penicillin allergy
Animal bites (Additional agent required)
- Severe penicillin allergy 

• Oral (sus, tab): 7.5mg/kg/dose, 8hrly; Treatment duration: 5 days
  (STG, PHC 2020; PHC 2023)

Post-exposure prophylaxis, rape and sexual assault (Additional agents required) 
- Sexually transmitted infections prophylaxis

Oral (sus, tab)

• Between 1-3 years: 500mg, as a single dose (and refer)
• Between 3-7 years: 600-800mg, as a single dose (and refer)
• Between 7-10 years: 1g, as a single dose (and refer)
• Older than 10 years: 2g, as a single dose (and refer)
  (STG, PHC 2020)

---

South African registered indications and dosages

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Treatment of infections caused by or suspected to be caused by anaerobic bacteria, including Bacteroides fragilis, Bacteroides sp, Fusobacteria, Eubacteria, Clostridia and anaerobic streptococci (additional agents required)

<12 years

• IV: 7.5mg/kg, 8hrly; Treatment duration: 7 days

THEN

• Oral (tab, sus): 7mg/kg, 8hrly as soon as oral medication can be given

> 12 years

• IV: 500mg, 8hrly, infused at 25mg/min; Treatment duration: 7 days

THEN

• Oral (tab, cap, sus): 400mg, 8hrly as soon as oral medication can be given

Prevention of anaerobic infections (additional agent/s may be required)

<12 years

• IV: 7.5mg/kg as an infusion, immediately before, during or after operation; Repeat 8hrly until oral medication can be given

THEN

• Oral (tab, sus): 7mg/kg, 8hrly as soon as oral medication can be given

>12 years

• IV: 500mg as an infusion, immediately before, during or after operation; Repeat 8hrly until oral medication can be given

THEN

• Oral (tab, cap, sus):  200-400mg, 8hrly, as soon as oral medication can be given

Trichomoniasis

Oral (tab)

• 1-3 years: 50mg, 8hrly; Treatment duration: 7 days
• 3-7 years: 100mg, 12hrly; Treatment duration: 7 days
• 7-10 years: 100mg, 8hrly; Treatment duration: 7 days
• >10 years: See adult dosage

Oral (cap)

• 3-10 years: 200mg, dly, in divided doses
• >10 years: See adult dosage

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Oral (tab): An alternative children's dose is 15 mg per kg body-weight daily in divided doses for 7 days

---

Oral (cap): If there is no response a second course of treatment may be given for 7 days after an interval of 4-6 weeks. The white cell count should be monitored

---

Giardiasis 

Oral (tab)

• 1-3 years: 400mg, dly; Treatment duration: 3 days
• 3-7 years: 600mg, dly; Treatment duration: 3 days
• 7-10 years: 1g, dly; Treatment duration: 3 days
• >10 years: See adult dosage

Oral (cap)

• Infants: 400mg, dly; Treatment duration: 3 days
• 3-7 years: 600mg, dly; Treatment duration: 3 days
• 7-10 years: 1g, dly; Treatment duration: 3 days
• >10 years: See adult dosage

Hepatitis - acute and chronic
Intestinal amoebiasis 

 Oral (tab)

• 1-3 years: 100-200mg, 8hrly; Treatment duration: 5-10 days
• 3-7 years: 100-250mg, 8hrly; Treatment duration: 5-10 days
• 7-10 years: 200-400mg, 8hrly; Treatment duration: 5-10 days
• >10 years: See adult dosage

---

Alternatively for children, a dose of 35-50 mg per kg body-weight daily in divided doses for 5-10 days has been suggested

---

Indications and dosages registered in other jurisdictions

General dosing range for treatment of established anaerobic infection: 

<8 weeks:

• IV/Oral (tab, sus): 15mg/kg administered as a single dose

OR

• IV/Oral (tab, sus): 7.5mg/kg, 12hrly

---

In newborns with a gestation <40 week, accumulation of metronidazole can occur during the first week of life, therefore concentrations of metronidazole in serum should preferably be monitored after a few days of therapy

---

Between >8weeks - 12 years:

• IV/Oral (tab, sus): 20-30mg/kg/day administered as a single dose; Treatment duration: 7 days; Max: 40mg/kg/24hrs

OR 

• IV/Oral (tab, sus): 7.5mg/kg, 8hrly; Treatment duration: 7 days; Max: 40mg/kg/24hrs

---

Oral medication should be substituted as soon as feasible

---

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Urogenital trichomoniasis

Between 1-10 years

• IV/Oral (tab, sus): 40mg/kg as a single dose; Treatment duration: 5-7 days; Max: 2000mg/24hrs 

OR

• IV/Oral (tab, sus): 15-30mg/kg, 8-12hrly; Treatment duration: 5-7 days; Max: 2000mg/24hrs 

>10 years

• See adult dosage

Bacterial vaginosis

>10 years

• IV/Oral (tab, sus): 400mg, 12hrly; Treatment duration: 5-7 days

OR

• IV/Oral (tab, sus): 2000mg, as a single dose

Amoebiasis

1-3 years

• IV: 100-200mg, 8hrly; Treatment duration: 5-10 days

3-7 years

• IV: 100-200mg, 6hrly; Treatment duration: 5-10 days

7-10 years

• IV: 200-400mg, 8hrly; Treatment duration: 5-10 days

>10 years

• IV: 400-800mg, 8hrly; Treatment duration: 5-10 days

- Invasive intestinal disease in susceptible subjects

1-3 years

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 5 days

3-7 years

• Oral (tab, sus): 200mg, 6hrly; Treatment duration: 5 days

7-10 years

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5 days

>10 years

• Oral (tab, sus): 800mg, 8hrly; Treatment duration: 5 days

- Intestinal disease in less susceptible subjects and chronic amoebic hepatitis

1-3 years

• Oral (tab, sus): 100mg, 8hrly; Treatment duration: 5-10 days

3-7 years

• Oral (tab, sus): 100mg, 6hrly; Treatment duration: 5-10 days

7-10 years

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 5-10 days

>10 years

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5-10 days

- Amoebic liver abscess
- Other forms of extra-intestinal amoebiasis

1-3 years

• Oral (tab, sus): 100mg, 8hrly; Treatment duration: 5 days

3-7 years

• Oral (tab, sus): 100mg, 6hrly; Treatment duration: 5 days

7-10 years

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 5 days

>10 years

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5 days

- Symptomless cyst passers

1-3 years

• Oral (tab, sus): 100-200mg, 8hrly; Treatment duration: 5-10 days

3-7 years

• Oral (tab, sus): 100-200mg, 6hrly; Treatment duration: 5-10 days

7-10 years

• Oral (tab, sus): 200-400mg, 8hrly; Treatment duration: 5-10 days

>10 years

• Oral (tab, sus): 400-800mg, 8hrly; Treatment duration: 5-10 days

---

Alternatively, doses may be expressed by body weight 35-50mg/kg, dly in 3 divided doses for 5-10 days; Max: 2400mg/24hrs

---

Giardiasis

1-3 years

• IV/Oral (tab, sus): 500mg, dly; Treatment duration: 3 days

3-7 years

• IV/Oral (tab, sus): 600-800mg, dly; Treatment duration: 3 days

7-10 years

• IV/Oral (tab, sus): 1000mg, dly; Treatment duration: 3 days

>10 years

• IV/Oral (tab, sus): 2000mg, dly; Treatment duration: 3 days

OR

• IV/Oral (tab, sus): 400mg, 8hrly; Treatment duration: 5 days

OR 

• IV/Oral (tab, sus): 500mg, 12hrly; Treatment duration: 7-10 days

---

Alternatively, as expressed in mg per kg of body weight: 15-40mg/kg/day divided in 2-3 divided doses

---

Acute ulcerative gingivitis

1-3 years

• Oral (tab, sus): 50mg, 8hrly; Treatment duration: 3 days

3-7 years

• Oral (tab, sus): 100mg, 12hrly; Treatment duration: 3 days

7-10 years

• Oral (tab, sus): 100mg, 8hrly; Treatment duration: 3 days

>10 years

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 3 days

Acute dental infections

>10 years

• Oral (tab, sus): 200mg, 8hrly; Treatment duration: 3-7 days

Leg ulcers and pressure sores

>10 years

• Oral (tab, sus): 400mg, 8hrly; Treatment duration: 7 days

Eradication of Helicobacter pylori in paediatric patients (additional agents required)

• IV/Oral (tab, sus): 20mg/kg, dly; Treatment duration: 7-14 days; Max: 500mg/12hrly

---

Official guidelines should be consulted before initiating therapy

---

Prophylaxis against anaerobic infection 
- Chiefly in the context of abdominal (especially colorectal) and gynaecological surgery

Newborns <40 weeks

• IV/Oral (sus): 10mg/kg, administered as a single dose before operation

<12 years

• IV/Oral (tab, sus): 20-30mg/kg, administered as a single dose 1-2 hours before surgery

OR

>10 years

• See adult dosage

Pregnancy

• Caution
• Metronidazole crosses the placental barrier
• Clinical data on a large number of exposed pregnancies and animal data did not show a teratogenic or foetotoxic effect. However unrestricted administration of nitroimidazolene to the mother may be associated with a carcinogenic or mutagenic risk for the unborn or newborn child
• Metronidazole should not be given during pregnancy unless the physician considers it essential; in these circumstances the short, high-dose regimens are not recommended

Breastfeeding

• Caution; not recommended
• Metronidazole is excreted in breast milk
• During breastfeeding, either breastfeeding or metronidazole should be discontinued

Fertility

• There are no clinical data relating to the effect of metronidazole on fertility
• Animal studies demonstrated adverse effects on the male reproductive system that are wholly or partially reversible after treatment withdrawal

Renal Impairment

• No dose adjustment recommended
  No routine adjustment in the dosage of metronidazole needs to be made in patients with renal failure undergoing intermittent peritoneal dialysis (IDP) or continuous ambulatory peritoneal dialysis (CAPD). However dosage reduction may be necessary when excessive concentrations of metabolites are found
  In patients undergoing haemodialysis, metronidazole should be re-administered immediately after haemodialysis

Hepatic Impairment

• Mild to moderate (Child-Pugh Classes A & B): Caution; no dose adjustment recommended
• Severe (Child-Pugh Class C): Caution; dose adjustment recommended
  IV/Oral dosage recommended to be decreased by 50%
  Metronidazole should be administered with caution to patients with hepatic encephalopathy. The daily dosage should be reduced to one third and may be administered once daily
  Patients with Cockayne syndrome should only use metronidazole after a careful benefit-risk assessment and only if no alternative treatment is available. Liver function tests must be performed just prior to the start of therapy, throughout and after end of treatment until liver function is within normal ranges, or until the baseline values are reached. If liver function tests become markedly elevated during treatment, metronidazole should be discontinued. Patients with Cockayne syndrome should be advised to immediately report any symptoms of potential liver injury to their physician and stop taking metronidazole

Elderly

• Caution; no dose adjustment recommended

Porphyria Information

• Probably not porphyrinogenic (PNP)

Drugs in Sport

• Permitted - No warnings

Central Nervous System Disorders

• Psychotic disorders
• Hallucinations
• Confusion
• Depressed mood
• Encephalopathy
  - Confusion
  - Fever
  - Headache
  - Hallucinations
  - Paralysis
  - Light sensitivity
  - Disturbances in sight and movement
  - Stiff neck
• Subacute cerebellar syndrome
  - Ataxia
  - Dysarthria
  - Gait impairment
  - Nystagmus
  - Tremor
• Drowsiness
• Dizziness
• Seizures
• Headaches
• Peripheral sensory neuropathy (intensive and/or prolonged treatment)
• Transient epileptiform seizures (intensive and/or prolonged treatment)
• Aseptic meningitis
• Insomnia (inj)
• Malaise (inj)

Cardiovascular Disorders

• Tachycardia (inj)
• Palpitations (inj)
• Chest pain (inj)

Respiratory Disorders

• Dyspnoea (inj)

Gastrointestinal Disorders

• Oral mucositis
• Furred tongue
• Nausea and vomiting
• Epigastric pain
• Diarrhoea
• Pancreatitis
• Glossitis (inj)
• Stomatitis (inj)
• Dry mouth (inj)
• Constipation (inj)
• Tongue discolouration (inj)
• Upper abdominal pain (inj)

Hepatobiliary Disorders

• Increase in hepatic enzymes (aspartate transaminase, alanine transaminase, alkaline phosphatase)
• Cholestatic or mixed hepatitis  
• Hepatocellular liver injury
• Hepatic failure
• Jaundice

Genitourinary Disorders

• Dark urine
• Dysuria (inj)

Endocrine and Metabolic Disorders

• Anorexia

Musculoskeletal Disorders

• Myalgia
• Arthralgia
• Muscle spasms (inj)

Skin and Subcutaneous Tissue Disorders

• Skin rashes
• Pustular eruptions
• Acute generalised exanthematous pustulosis
• Pruritis
• Flushing
• Erythema multiforme
• Stevens-Johnson syndrome
• Toxic epidermal necrolysis
• Fixed drug eruption
• Swelling face (inj)
• Hyperhidrosis (inj)
• Injection site reaction (inj)

Immune, Blood and Lymphatic System Disorders

• Agranulocytosis
• Neutropenia
• Thrombocytopenia
• Pancytopenia
• Leucopenia
• Anaphylaxis
• Angioedema
• Urticaria
• Fever
• Hypersensitivity
• Eosinophilia (inj)
• Jarisch-Herxheimer reaction (inj)
• Mucosal inflammation (inj)
• Chills (inj)
• Peripheral oedema (inj)

Sensory Disorders

• Diplopia
• Myopia
• Optic neuropathy
• Optic neuritis
• Impaired hearing
• Hearing loss (including sensorineural)
• Tinnitus
• Taste disorders

• Disulfiram
• Warfarin type oral anticoagulants
• Lithium
• Barbiturates
• Phenobarbital
• Phenytoin
• 5-fluorouracil
• Ciclosporin
• Busulfan
• Mycophenolate
• Cimetidine
• Oestrogens
• Carbamazepine
• Vecuronium (inj)
• Cholestyramine (inj)
• CYP3A4 substrates (inj)
• Amiodarone (inj)
• Tacrolimus (inj)
• Quinidine (inj)

Other interactions

• Alcohol
• Interference with lab tests (see additional prescribing points)

None routine. Specific cases may require

• Full blood count
• Hepatic function

Additional observations

• Monitor for neurologic symptoms

Tablet 200mg, Tablet 400mg, Suspension 200mg/5ml - EML (Primary)

Injection 500mg/100ml - EML (Hospital)

All other forms - Non-EML 

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Interference with laboratory tests

• Metronidazole may immobilize Treponema and thus may lead to falsely positive Nelson's test
• Metronidazole may interfere with serum aspartate transaminase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), triglycerides, and glucose hexokinase determinations. Metronidazole causes an increase in ultraviolet absorbance at 340 nm resulting in falsely decreased values

The selective action of metronidazole against anaerobes and anoxic and hypoxic cells is due to the mode of action. The nitro group of metronidazole acts as electron acceptor and is thus reduced to a chemically reactive drug form. This produces biochemical lesions in the cells, thus causing death. The major site of action is believed to be DNA, where it causes loss of the helical structure and inhibits synthesis.

Spectrum of activity: B. fragilis, F. necrophorum, Prevotella sp., C. difficile, Clostridium sp., Bacteroides sp., Fusobacteria,Clostridia, Eubacteria, anaerobic cocci, Gardnerella vaginalis, Trichomonas vaginalis,Other species of trichomonads, Balantidium coli, Entamoeba histolytica, Giardia lamblia, causative organisms of acute ulcerative gingivitis

Capsule 200mg

• Narobic (Alliance)

Tablet 200mg

• Acuzole (Pharmascript)
• Adco-Metronidazole (Adcock Ingram)
• Ambral (Thebe)
• Anaerobyl (Medicine Dev)
• Bemetrazole (Ranbaxcy)
• Flagyl (Sanofi) originator
• Medamet (Caps Pharma)
• Metagyl (Oethmaan Biosims)
• Metazol (Akacia)
• Merck metronidazole (Xixia)
• Metronidazole Dezzo (Dezzo)
• Sandoz metronidazole (Sandoz)
• Trichazole (Pharmacare)

Tablet 400mg

• Acuzole (Pharmascript)
• Adco-metronidazole (Adcock Ingram)
• Amzole (Innovata)
• Anaerobyl (Medicine Dev)
• Bemetrazole (Ranbaxy Pharmaceuticals)
• Bio-metronidazole (Biotech)
• Dynametron (Akacia)
• Flagyl (Sanofi) originator
• Metagyl Forte (Oethmaan Biosims)
• Metazol (Alliance Pharma)
• Metrostat (Adcock Ingram)
• Metrazole (Pharmacorp)
• Metronidazole Dezzo (Dezzo)
• Nidasall 400 (Innovata Pharmaceuticals)
• Sandoz metronidazole (Sandoz)
• Trichazole (Pharmacare)

Suspension (per 5ml) 200mg

• Flagyl (Sanofi) originator

Injection (per 100ml) 500mg

• Bio-Metronidazole (Biotech)
• Flagyl (Sanofi) originator
• Metronidazole B braun (B Braun)
• Metris (Dezzo Trading)
• Sabax metronidazole (Adcock Ingram) 
• Trichazole ( Fresenius Kabi)

Suppository 500mg

• Flagyl (Sanofi) originator

Suppository 1g

• Flagyl (Sanofi) originator

Also available in the following form: Gel.