Usage
- Medical Conditions: Neomycin is an aminoglycoside antibiotic primarily used for bowel preparation before surgery to reduce the risk of infection. It’s also used topically for skin infections and ophthalmic infections. Orally, it can be used to treat hepatic encephalopathy.
- Pharmacological Classification: Antibiotic.
- Mechanism of Action: Neomycin inhibits bacterial protein synthesis by irreversibly binding to the 30S ribosomal subunit, ultimately leading to bacterial cell death.
Alternate Names
- International/Regional Variations: Framycetin, Mycifradin.
- Brand Names: Neo-Fradin, Neo-Tab, Nivemycin.
How It Works
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Pharmacodynamics: Neomycin exerts its bactericidal effect by irreversibly binding to specific proteins within the bacterial 30S ribosomal subunit. This binding interferes with the accurate reading of messenger RNA (mRNA) by the ribosome, leading to miscoded proteins and the inhibition of protein synthesis. This ultimately causes bacterial cell death. Neomycin is particularly effective against gram-negative bacteria.
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Pharmacokinetics:
- Absorption: Oral absorption is minimal (around 3%). Topical application results in limited systemic absorption. Higher absorption can occur in individuals with bowel inflammation or damage.
- Distribution: If absorbed systematically, it is distributed widely in tissues and can cross the placental barrier. It has poor penetration into the cerebrospinal fluid.
- Metabolism: Neomycin is not extensively metabolized.
- Elimination: Primarily excreted unchanged via the kidneys. Dose adjustment is necessary for patients with renal impairment.
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Mode of Action: Binds to the 30S ribosomal subunit of bacteria, interrupting protein synthesis.
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Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Inhibits bacterial protein synthesis.
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Elimination Pathways: Predominantly renal excretion.
Dosage
Standard Dosage
Adults:
- Bowel Preparation: 1 gram every hour for 4 hours, then 1 gram every 4 hours for 20 hours. Or, 1 gram at 1 PM, 2 PM, and 11 PM the day before an 8 AM surgery. Often combined with erythromycin base or metronidazole.
- Hepatic Encephalopathy: 4-12 grams daily in divided doses for 5-6 days for hepatic coma. Up to 4 grams daily for chronic hepatic insufficiency.
- Other: 1-3 grams every six hours for 5-6 days.
Children:
- Bowel Preparation: 90 mg/kg/day in 6 divided doses for 2-3 days.
- Hepatic Encephalopathy: 50-100 mg/kg/day in 3 divided doses for 5-6 days (maximum 12 grams/day).
- Other: 14.7 mg/kg every 4 hours for 3 days.
- Pediatric Safety: Neonates and premature infants are at increased risk of ototoxicity (hearing loss). Use with caution.
Special Cases:
- Elderly Patients: Increased risk of nephrotoxicity and ototoxicity. Close monitoring of renal function and hearing is recommended. Dose reduction may be needed.
- Patients with Renal Impairment: Dosage reduction is required. Close monitoring of renal function and drug levels.
- Patients with Hepatic Dysfunction: Dosage adjustment is generally not needed except in the context of hepatic encephalopathy.
- Patients with Comorbid Conditions: Caution advised in patients with neuromuscular disorders (myasthenia gravis, Parkinson’s disease) as neomycin can exacerbate muscle weakness.
Clinical Use Cases
Dosing in specific clinical settings is covered above (Bowel Preparation, Hepatic Encephalopathy). Neomycin is not typically used in situations like intubation, surgical procedures (except for bowel preparation), mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
- Renal impairment: Reduce dosage and monitor drug levels.
- Hepatic impairment: Generally no adjustment needed except in the context of hepatic encephalopathy.
Side Effects
Common Side Effects
Rare but Serious Side Effects
- Nephrotoxicity (kidney damage)
- Ototoxicity (hearing loss, tinnitus, vertigo)
- Neuromuscular blockade (muscle weakness, respiratory paralysis)
- Allergic reactions
Long-Term Effects
- Permanent hearing loss
- Kidney damage
Adverse Drug Reactions (ADR)
- Anaphylaxis
- Severe nephrotoxicity or ototoxicity
Contraindications
- Hypersensitivity to neomycin or other aminoglycosides
- Intestinal obstruction
- Inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis)
- Myasthenia gravis
Drug Interactions
- Other aminoglycosides (increased risk of nephrotoxicity and ototoxicity)
- Nephrotoxic drugs (e.g., amphotericin B, cisplatin, vancomycin)
- Ototoxic drugs (e.g., loop diuretics)
- Neuromuscular blocking agents (increased risk of respiratory paralysis)
- Oral anticoagulants (enhanced effect)
- Digoxin, penicillin V, vitamin B12, methotrexate, 5-fluorouracil (decreased absorption)
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Category D (evidence of human fetal risk, but potential benefits may outweigh risks in certain situations). Use only if clearly needed and the benefit outweighs the risk.
- Fetal Risks: Ototoxicity (hearing loss), nephrotoxicity.
- Breastfeeding: Neomycin may pass into breast milk. Monitor breastfed infants for gastrointestinal effects (diarrhea, candidiasis). Consider discontinuing breastfeeding or the drug.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit.
- Side Effects: Nausea, vomiting, diarrhea, nephrotoxicity, ototoxicity, neuromuscular blockade.
- Contraindications: Hypersensitivity, intestinal obstruction, inflammatory bowel disease, myasthenia gravis.
- Drug Interactions: Other aminoglycosides, nephrotoxic and ototoxic drugs, neuromuscular blocking agents.
- Pregnancy & Breastfeeding: Category D; may pass into breast milk.
- Dosage: Varies depending on indication; see dosage section.
- Monitoring Parameters: Renal function, hearing tests, signs of neuromuscular blockade.
Popular Combinations
- Bowel Preparation: Neomycin + erythromycin base or metronidazole.
Precautions
- Assess renal function and hearing before and during treatment.
- Monitor for signs of hypersensitivity and neuromuscular blockade.
- Use with caution in elderly patients and those with renal impairment.
- Avoid concurrent use of other nephrotoxic or ototoxic drugs.
- Patients with bowel obstruction or inflammatory bowel disease should not take oral neomycin.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Neomycin?
A: Dosage varies depending on the indication and patient factors. See the dosage section for detailed information.
Q2: What are the most common side effects of neomycin?
A: Nausea, vomiting, and diarrhea are the most common side effects.
Q3: What are the serious side effects of neomycin?
A: Nephrotoxicity, ototoxicity, and neuromuscular blockade are the most serious side effects.
Q4: Is neomycin safe to use during pregnancy?
A: No, neomycin is classified as pregnancy category D and should only be used if clearly needed and the benefit outweighs the risk.
Q5: Can neomycin be used in patients with renal impairment?
A: It can be used, but dosage adjustment is crucial, and careful monitoring is needed.
Q6: What are the contraindications to using neomycin?
A: Hypersensitivity to neomycin, intestinal obstruction, inflammatory bowel disease, and myasthenia gravis are contraindications.
Q7: How does neomycin interact with other medications?
A: Neomycin interacts with other aminoglycosides, nephrotoxic drugs, ototoxic drugs, neuromuscular blocking agents, and some oral medications. See drug interactions section for details.
Q8: What should patients be advised regarding neomycin treatment?
A: Patients should report any hearing changes, signs of kidney problems, or muscle weakness. They should also complete the full course of treatment even if they feel better. Advise them to avoid concurrent use of alcohol and other potentially ototoxic drugs.
Q9: What monitoring should be done for patients on neomycin?
A: Monitor renal function, hearing (audiometry if possible), and look for signs of neuromuscular blockade.
Q10: Can neomycin be given to children?
A: Yes, but with caution, especially in neonates and premature infants due to the risk of ototoxicity. Pediatric dosage adjustments are necessary.
