Can Neomycin Cause Paresthesias?
Yes, neomycin can cause paresthesias through neurotoxic effects, though this adverse effect is well-documented in FDA labeling and occurs even with oral administration at recommended doses. 1
Mechanism and Clinical Presentation
Neomycin-induced neurotoxicity manifests as peripheral nerve symptoms including paresthesias, which represent one of several neurological complications associated with this aminoglycoside antibiotic. 2 The FDA explicitly warns that neurotoxicity, including peripheral paresthesias, can occur following oral use of neomycin even when used in recommended doses. 1
Specific Neurotoxic Effects
Peripheral neuropathy: Neomycin causes paresthesias as part of its peripheral nerve toxicity profile, characterized by abnormal sensations, motor weakness, or sensory impairment. 2
Central nervous system involvement: Beyond peripheral effects, neomycin can cause NMDA receptor activation leading to neuronal damage, suggesting both peripheral and central mechanisms of neurotoxicity. 3
Neuromuscular blockade: In addition to paresthesias, neomycin can cause neuromuscular blockage and respiratory paralysis, particularly in patients receiving anesthetics or neuromuscular blocking agents. 1
Risk Factors and Clinical Context
High-Risk Populations
Renal impairment: The risk of neurotoxicity and paresthesias is substantially greater in patients with impaired renal function, as neomycin clearance depends on kidney function. 1
Systemic absorption: Although neomycin is poorly absorbed orally, small amounts are absorbed through intact intestinal mucosa, and systemic absorption increases the risk of toxic reactions including neurotoxicity. 1
Concurrent medications: Patients receiving other neurotoxic drugs (bacitracin, cisplatin, vancomycin, amphotericin B, polymyxin B, colistin, viomycin) face additive toxicity risks. 1
Dose and Duration Considerations
Higher doses and prolonged therapy: Neurotoxicity risk increases with doses exceeding recommendations and treatment duration beyond standard protocols. 1
Malabsorption syndrome: Oral neomycin doses of 12 grams per day can produce malabsorption of multiple substances, potentially contributing to neurological complications. 1
Monitoring and Prevention
Essential Monitoring Parameters
Neurological assessment: Serial monitoring for paresthesias and other neurological symptoms should be performed, especially in high-risk patients. 1
Renal function: Tests including serum creatinine, BUN, and creatinine clearance should be performed prior to and periodically during therapy, as renal insufficiency increases neurotoxicity risk. 1
Eighth nerve function: While primarily for ototoxicity monitoring, vestibular and audiometric tests should be performed as part of comprehensive neurotoxicity surveillance. 1
Clinical Management
Immediate discontinuation: If paresthesias or other neurotoxic symptoms develop, consideration should be given to reducing dosage or discontinuing therapy entirely. 1
Avoid concurrent neurotoxins: The concurrent use of neomycin with other potentially neurotoxic drugs should be avoided because toxicity may be additive. 1
Patient counseling: Patients or family members should be informed of possible toxic effects on peripheral nerves before administering the drug. 1
Important Clinical Caveats
Delayed onset: Neurotoxic effects may not manifest immediately during therapy, and symptoms can develop after treatment initiation. 1
Cross-allergenicity: Cross-allergenicity among aminoglycosides has been demonstrated, so patients with prior aminoglycoside neurotoxicity may be at higher risk. 1
Muscular disorders: Neomycin should be used with extreme caution in patients with myasthenia gravis or parkinsonism, as it may aggravate muscle weakness through curare-like effects on the neuromuscular junction. 1
Topical absorption: Neomycin is quickly and almost totally absorbed from body surfaces after local irrigation, meaning even topical use during surgical procedures can cause systemic neurotoxicity. 1