Neomycin Side Effects
Neomycin can cause serious adverse effects including nephrotoxicity, ototoxicity, and neuromuscular blockade, with ototoxicity often being permanent even after discontinuation of the drug. 1
Major Side Effects
Ototoxicity
- Irreversible deafness can occur even with topical application or irrigation of wounds 2, 3
- Hearing loss may be progressive despite withdrawal of neomycin 3
- Risk of ototoxicity increases with:
Nephrotoxicity
- Acute renal failure can develop, especially with systemic absorption 2
- Usually reversible with proper management and discontinuation 2, 3
- Requires monitoring of renal function during treatment 1
Neuromuscular Blockade
- Can occur regardless of renal function status 1
- Particularly concerning in patients with pre-existing muscular disorders like myasthenia gravis 1
- May aggravate muscle weakness due to curare-like effect on neuromuscular junction 1
Gastrointestinal Side Effects
- Nausea, vomiting, and diarrhea are the most common adverse reactions 1
- Malabsorption syndrome with prolonged therapy, characterized by:
- Increased fecal fat
- Decreased serum carotene
- Reduced xylose absorption 1
- Inhibits gastrointestinal absorption of:
- Penicillin V
- Oral vitamin B-12
- Methotrexate
- 5-fluorouracil
- Digoxin 1
- May enhance the effect of coumarin anticoagulants by decreasing vitamin K availability 1
Allergic Reactions
- Cross-allergenicity among aminoglycosides has been demonstrated 1
- Neomycin allergy often manifests as contact dermatitis (delayed-type immune response) 6
- Typically appears as erythematous, pruritic nodule or papule 48-96 hours after exposure 6
Risk of Microbial Overgrowth
- May result in overgrowth of nonsusceptible organisms, particularly fungi 1
- Requires appropriate antifungal therapy if overgrowth occurs 1
Monitoring Recommendations
To avoid nephrotoxicity and eighth nerve damage, the following should be performed before and during therapy:
- Urinalysis for increased protein excretion, decreased specific gravity, casts and cells
- Renal function tests (serum creatinine, BUN, creatinine clearance)
- Tests of vestibulocochlear nerve function
- Serial vestibular and audiometric tests, especially in high-risk patients 1
Special Precautions
- Elderly patients may have reduced renal function not evident in routine screening tests 1
- Caution with concurrent use of other nephrotoxic/ototoxic drugs due to potential enhancement of toxicity 1
- Caution with concurrent use of aminoglycosides and polymyxins 1
- Monitor digoxin serum levels when co-administered with neomycin 1
Practical Considerations
- Temporary gastrointestinal side effects may occur even with short-term use 7
- Systemic absorption can occur from topical application to large wounds, resulting in "high output" renal failure and hearing loss 2
- Benefits of neomycin irrigation should be weighed against the risk of permanent hearing impairment 3