Gentamicin Topical and Magnesium: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Gentamicin Topical
Magnesium
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Neuromuscular weakness
Interaction Deep Dive
Concomitant magnesium and aminoglycosides can produce neuromuscular weakness and possibly paralysis3.
Why it happens (mechanism)
Decreased acetylcholine release
Literature reports
1 report — tap to read
a) Anticholinergic release from presynaptic cholinergic neurons can be impaired by aminoglycosides but is clinically insignificant in patients with normal cholinergic function since there is an excessive reserve of acetylcholine. Magnesium also acts as a neuromuscular blocker by causing decreased acetylcholine release from motor nerve impulses 1. In patients receiving aminoglycosides and magnesium concurrently, a decrease in acetylcholine release may be sufficient to impair neuromuscular transmission. This has been demonstrated in animal studies 2.
Common questions
Can I take Gentamicin Topical and Magnesium together?
Neuromuscular weakness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Gentamicin Topical and Magnesium interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Gentamicin Topical or Magnesium need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (3)
- Gilman AG, Goodman LS, & Gilman AGilman AG, Goodman LS, & Gilman A (Eds): Goodman and Gilman's The Pharmacological Basis of Therapeutics, 6th. Macmillan Publishing Co, New York, NY, 1980.
- L'Hommedieu CS, Nicholas D, Armes DA, et al: Potentiation of magnesium sulfate induced neuromuscular weakness by gentamicin, tobramycin, and amikacin. J Pediatr 1983; 102:629-631.
- Watson A, Coffey L, Keogh B, et al: Severe hypomagnesaemia and hypocalcaemia following gentamicin therapy. Ir Med J 1983; 76:381-383.
Keep reading about Gentamicin Topical
Keep reading about Magnesium
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