Usage
Furazolidone + Metronidazole is a combination antibiotic used to treat bacterial and protozoal infections, particularly gastrointestinal infections like giardiasis, amoebiasis, and bacterial diarrhea. It’s also effective against infections caused by susceptible gram-positive and gram-negative bacteria.
- Pharmacological Classification: Antibiotic, Antiprotozoal
- Mechanism of Action: Furazolidone inhibits bacterial and protozoal protein synthesis, while metronidazole damages DNA of anaerobic bacteria and protozoa, disrupting their growth and replication.
Alternate Names
No widely recognized alternate names exist for this specific combination, though it might be locally referred to by various names depending on the region or manufacturer.
- Brand Names: Metrogyl F, Furazole M, Anaerid F.
How It Works
- Pharmacodynamics: Furazolidone disrupts protein synthesis by interfering with ribosomal function. Metronidazole forms toxic free radicals that damage DNA and other essential macromolecules within anaerobic microorganisms.
- Pharmacokinetics: Both drugs are absorbed orally. Furazolidone is primarily metabolized in the liver and excreted in urine. Metronidazole is also metabolized in the liver, with both renal and hepatic excretion.
- Mode of Action:
- Furazolidone: Inhibits protein synthesis, disrupting ribosomal function.
- Metronidazole: Damages DNA and other essential macromolecules of susceptible anaerobic microorganisms by forming free radicals.
- Receptor Binding/Enzyme Inhibition: Furazolidone acts as a monoamine oxidase inhibitor (MAOI). Metronidazole’s mechanism involves interaction with microbial DNA.
- Elimination Pathways: Both drugs are primarily metabolized in the liver. Metabolites and some parent drug are excreted in urine.
Dosage
Standard Dosage
Adults:
- Standard dose: Furazolidone 100 mg + Metronidazole 200-400mg four times a day.
- Duration: 5-10 days depending on the infection.
Children:
- Dose is based on body weight (6mg/kg/day furazolidone, 20-30mg/kg/day metronidazole divided into multiple doses).
- Use in infants under one month is generally avoided due to the risk of hemolytic anemia. Pediatric use requires careful monitoring.
Special Cases:
- Elderly Patients: Dose adjustments may be necessary, especially for high doses, due to age-related decline in renal and hepatic function. Monitor closely for adverse events.
- Patients with Renal Impairment: Dose adjustments are necessary based on creatinine clearance. Monitor drug levels closely.
- Patients with Hepatic Dysfunction: Dose modifications required due to reduced metabolic capacity. Monitor liver function tests and drug levels.
- Patients with Comorbid Conditions: Use with caution in patients with G6PD deficiency, neurological conditions, or history of seizures. Avoid alcohol during and shortly after treatment.
Clinical Use Cases
Dosage guidelines for these clinical scenarios aren’t specifically defined for this combined formulation. Treatment in these contexts usually involves parenteral administration of metronidazole.
- Intubation
- Surgical Procedures
- Mechanical Ventilation
- Intensive Care Unit (ICU) Use
- Emergency Situations (e.g., status epilepticus, cardiac arrest)
Dosage Adjustments
Dosages should be adjusted based on renal/hepatic impairment and response to therapy. Monitor for adverse effects and adjust accordingly.
Side Effects
Common Side Effects
- Nausea
- Vomiting
- Headache
- Metallic taste
- Darkened urine
- Dry mouth
Rare but Serious Side Effects
- Peripheral neuropathy
- Seizures
- Stevens-Johnson syndrome
- Psychotic reactions
Long-Term Effects
Long-term use of this drug combination is generally avoided due to the potential for toxicity, especially with metronidazole.
Adverse Drug Reactions (ADR)
- Hypersensitivity reactions (rash, itching, swelling)
- Disulfiram-like reaction (flushing, nausea, vomiting, headache) when taken with alcohol
Contraindications
- Hypersensitivity to either Furazolidone or Metronidazole, or any nitroimidazole derivative
- First trimester of pregnancy (Metronidazole)
- G6PD deficiency (Furazolidone)
- Patients with Cockayne syndrome
Drug Interactions
- Alcohol (Disulfiram-like reaction with Metronidazole)
- Disulfiram
- Warfarin and other anticoagulants
- Lithium
- Phenytoin and other anticonvulsants
- Tyramine-containing foods (Furazolidone)
Pregnancy and Breastfeeding
- Pregnancy: Contraindicated in the first trimester. Use with caution in later trimesters only if potential benefit outweighs risk.
- Breastfeeding: Metronidazole is excreted in breast milk. Advise mothers to express and discard milk during treatment and for 24-48 hours after the last dose, or consider temporarily discontinuing breastfeeding.
Drug Profile Summary
- Mechanism of Action: Furazolidone: Inhibits protein synthesis. Metronidazole: Damages microbial DNA.
- Side Effects: Nausea, vomiting, headache, metallic taste, darkened urine, peripheral neuropathy (rare).
- Contraindications: Hypersensitivity, first trimester pregnancy, G6PD deficiency, Cockayne syndrome.
- Drug Interactions: Alcohol, Disulfiram, anticoagulants, lithium, anticonvulsants.
- Pregnancy & Breastfeeding: Contraindicated in the first trimester; use with caution in later trimesters. Advise discarding breast milk during and after treatment.
- Dosage: Adults: 100 mg furazolidone + 200-400mg metronidazole four times/day. Pediatric: Weight-based.
- Monitoring Parameters: Complete blood count, liver function tests, renal function tests, signs of neurological toxicity.
Popular Combinations
This drug is commonly used as a standalone combination. Combining it with other antibiotics is generally not recommended due to increased risk of side effects and potential loss of efficacy.
Precautions
- Obtain a detailed medical history, including allergy information and current medications.
- Monitor closely for side effects, particularly neurological and hematological effects.
- Screen for G6PD deficiency before prescribing furazolidone.
- Counsel patients to avoid alcohol during and shortly after treatment with metronidazole.
- Monitor liver and kidney function in patients with pre-existing hepatic or renal disease.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Furazolidone + Metronidazole?
A: Adults: 100 mg Furazolidone + 200-400 mg Metronidazole, four times daily. Pediatric dosage is weight-based (6mg/kg/day furazolidone, 20-30mg/kg/day metronidazole).
Q2: What are the most common side effects?
A: Nausea, vomiting, headache, metallic taste, darkened urine, and dry mouth.
Q3: What are the contraindications for this medication?
A: Hypersensitivity, first trimester of pregnancy, G6PD deficiency, and Cockayne Syndrome.
Q4: Can this medication be used in pregnant women?
A: Contraindicated in the first trimester. Use with caution in later trimesters only if benefit outweighs risk.
Q5: Can this medication be used in breastfeeding mothers?
A: Metronidazole is excreted in breast milk. Mothers should discard breast milk during treatment and for 24-48 hours after the last dose, or consider temporarily discontinuing breastfeeding.
Q6: What are the important drug interactions to be aware of?
A: Alcohol (disulfiram-like reaction with metronidazole), disulfiram, warfarin, lithium, phenytoin, and tyramine-containing foods (with furazolidone).
Q7: How long does the treatment typically last?
A: 5-10 days depending on the type and severity of the infection.
Q8: What should I do if a patient misses a dose?
A: Take the missed dose as soon as remembered unless it is close to the next scheduled dose. Do not double the dose.
Q9: What is the mechanism of action of this combination drug?
A: Furazolidone inhibits protein synthesis and metronidazole damages DNA of anaerobic bacteria and protozoa.
Q10: How should I monitor patients taking this medication?
A: Monitor for side effects, especially neurological and hematological. Perform regular blood counts, liver function tests, and renal function tests if indicated.
