Nitrofurans:

• These are group of synthetic antibacterial compounds which contain 5-nitrofuran ring.
• These agents include furazolidine, furaltadone, nifuraldezone and nifurprazine

Mechanism of action:

These are types of pro drug which diffuses into susceptible bacteria

Bacterial enzymes reduce these drug into reactive metabolites

These metabolites blocks oxidative decarboxylation of pyruvate to acetyl coA

Deprivation of energy in bacteria

Antibacterial action of nitrofurans

Antimicrobial spectrum:

• These have broad spectrum of activity against both gram -ve and gram +ve bacteria
• It is also active against coccidia, trichomonads, amoebae and giardia
• It is primarily bacteriostatic but may become bactericidal at high concentration
• Presence of pus, blood, plasma and milk may reduce antibacterial activity.

Bacterial resistance:

• Bacterial resistance develops slowly
• Resistance is mainly by chromosomal mutation
• It may show complete cross-resistance but no cross-resistance with any other antibacterial agent.

Pharmacokinetics:

• They are either absorbed or after absorption they are rapidly eliminated that no systemic inhibitory concentration is achieved in body varies with individual drugs.
• Administration along with feed promotes absorption
• Acidic urine promotes passive reabsorption of nitrofurans in renal tubule and also decreases their overall urine concentration.

Side effects/Adverse effects:

• GI disturbances (nausea, vomiting, diarrhoea)
• CNS signs (excitement, tremors, convulsion and peripheral neuritis)
• Depression of spermatogenesis, disturbances of eye and poor weight gain
• Hypersensitivity

Contraindications and precautions:

• In patients who are hypersensitive to nitrofurans
• It is not recommended in food producing animal
• It should not be used by parenteral route due to systemic toxicity

Clinical uses:

• It is used topically for cutaneous infection and wound dressing in all species
• It is used as urinary antiseptics in dogs and cats

Nitrofurantoin:

• It is synthetic nitrofuran used mainly for prevention and treatment of urinary tract infections

Antimicrobial spectrum:

• It has wide range of antimicrobial activity including Staphylococcus aureus, Escherichia coli, Aerobacter aerogenes and species of Salmonella, Shigella, Klebsiella, Enterobacter and Corneybacterium.
• Pseudomonas aeruginosa & proteus, Serratia and Actinobacter species show little or no susceptibility to nitrofurantoin
• Antibacterial activity of nitrofurantoin is high in acidic urine

Pharmacokinetics:

• It is rapidly and almost completely absorbed from G.I tract
• They are rapidly excreted in urine via glomerular filtration
• Peak urine levels occur within 30 minutes of oral dosing
• Food enhances the oral absorption of nitrofurantoin
• Plasma half-lives is almost 20 minutes.

Side effects/Adverse effects:

• Nausea, vomiting, diarrhoea
• CNS disorders

Contraindications and precautions:

• It is contraindicated in patients with glucose-6-phosphate dehydrogenase deficiency because of risk of extravascular hemolysis resulting in anemia.

Uses:

• It is used exclusively for treatment of lower UTI in small animals

Dose:

Dogs & cats: 4 mg/kg, PO, 3 times daily

Horses: 2.5-4.5 mg/kg, PO, 3 times daily

Furazolidone:

• It is synthetic nitrofuran used for enteric infection

Antimicrobial spectrum:

• It has wide spectrum of activity that includes Clostridium, Salmonella, Shigella, Staphylococcus & Streptococcus species and E.coli
• It is also active against Giardia, Trichomonas, Coccidia and Histomonas

Pharmacokinetics:

• They are poorly absorbed from G.I tract after oral administration
• After absorption, they are rapidly metabolized and excreted in urine
• Distributed into CSF.

Side effects/Adverse effects:

• Inappetence, nausea, vomiting, abdominal cramps and diarrhoea
• Tremors, ataxia, convulsions and visual impairment

Contraindications and precautions:

• It should not be administered with SSRI antidepressant, tricyclic antidepressant and triptans.

Indications:

• In treatment of enteric infections
• In bacterial enteritis, food poisoning, diarrhoea, bacillary dysentery and giardiasis
• It is used topically for subcutaneous infection

Dose:

For enteric infections

Dogs: 2.2 mg/kg, PO, 3 times daily for 7 days

Cats: 4 mg/kg, PO, 2 times daily for 7-10 days

Horses: 4mg/kg, PO, 3 times daily

Birds: 100-200 mg/L in drinking water

For coccidiosis

Dogs and cats: 8-20mg/kg, PO, 3 times daily for 7 days