Neomycin is an aminoglycoside antibiotic derived from *Streptomyces fradiae*. It is primarily used topically and orally due to its significant systemic toxicity when administered parenterally. It is bactericidal, acting by inhibiting bacterial protein synthesis. In the Indian context, it is widely used for topical skin infections, ophthalmic conditions, and as an oral preparation for hepatic encephalopathy and preoperative bowel sterilization.
Adult: **Topical:** Apply a thin layer to affected area 1-3 times daily. **Ophthalmic:** 1-2 drops in the affected eye(s) every 4-6 hours, or ointment applied 2-3 times daily. **Otic:** 2-3 drops in the affected ear 3-4 times daily. **Oral (Hepatic Encephalopathy):** 1-3 g every 6 hours for 5-6 days. **Oral (Bowel Prep):** 1 g each of neomycin and erythromycin base at 1 PM, 2 PM, and 11 PM on the day before surgery (combined with mechanical cleansing).
Note: **Oral:** Administer with or without food. For bowel prep, follow specific protocol with laxatives. **Topical:** Clean and dry area before application. Do not cover with occlusive dressings unless advised. **Ophthalmic:** Do not touch dropper tip to eye. Wait 5 minutes between different eye drops. **Otic:** Warm drops in hand before instillation. Lie with affected ear upward for 5 minutes.
Neomycin is a bactericidal aminoglycoside. It binds irreversibly to the 30S ribosomal subunit of susceptible bacteria, specifically to the 16S rRNA of the subunit. This binding interferes with the initiation complex of protein synthesis, causes misreading of the genetic code on mRNA, and leads to the incorporation of incorrect amino acids into the growing polypeptide chain. The result is the production of non-functional or toxic proteins and bacterial cell death.
Pregnancy: **Category D (US FDA).** Aminoglycosides cross the placenta. Risk of fetal ototoxicity. Use only if potential benefit justifies the potential risk to the fetus. Topical use on small areas is considered low risk.
Driving: Generally no effect. However, if systemic ototoxicity occurs (vertigo, dizziness), it can impair the ability to drive or operate machinery.
| Other Ototoxic drugs (e.g., Furosemide, Ethacrynic acid) | Increased risk of hearing loss and vestibular damage. | Major |
| Other Nephrotoxic drugs (e.g., Vancomycin, Amphotericin B, Cisplatin) | Increased risk of acute kidney injury. | Major |
| Neuromuscular blocking agents (e.g., Succinylcholine, Tubocurarine) | Potentiation of neuromuscular blockade, leading to prolonged respiratory depression. | Major |
| Oral Anticoagulants (e.g., Warfarin) | Neomycin may reduce vitamin K production by gut flora, potentially enhancing anticoagulant effect. | Moderate |
| Digoxin, Methotrexate | Reduced absorption of these drugs from the GI tract due to neomycin-induced mucosal damage or altered flora. | Moderate |
| Penicillin V | Neomycin may reduce its absorption. | Moderate |
Same composition (Neomycin (NA)), different brands: