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Does Tobramycin Interact with Penicillin G?

Tobramycin and Penicillin G have a unknown drug interaction according to U.S. FDA drug labeling data. Combined with tobramycin results in synergistic bactericidal effect in vitro against certain strains of Enterococcus faecalis, but not synergistic against Enterococcus faecium. The mechanism involves aminoglycoside combined with antibiotic that interferes with cell-wall synthesis. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Unknown
Tobramycin Class
Aminoglycoside Antibacterial
Management
Consult your pharmacist
Data Source
U.S. FDA via OpenFDA

How This Interaction Works

The interaction between Tobramycin and Penicillin G occurs because aminoglycoside combined with antibiotic that interferes with cell-wall synthesis. Clinically, this means combined with tobramycin results in synergistic bactericidal effect in vitro against certain strains of enterococcus faecalis, but not synergistic against enterococcus faecium.

What To Tell Your Doctor or Pharmacist

If you are taking Tobramycin and your doctor is considering prescribing Penicillin G (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Never stop or change either medication without first consulting your healthcare provider
💊 Tobramycin(Bethkis)+💊 Penicillin G(Penicillin G Potassium)

Severity & Interaction Details

ℹ️
unknown
Interaction documented — severity unclassified
The FDA label notes an interaction but the severity is not classified in our dataset.
Severity scale
MinorContra
On record
Yes
Drug A class
Aminoglycoside Antibacterial
Drug B class
—
Source
NLP:tobramycin

What this means in plain English

Combined with tobramycin results in synergistic bactericidal effect in vitro against certain strains of Enterococcus faecalis, but not synergistic against Enterococcus faecium.

About Tobramycin and Penicillin G

Tobramycin is an Aminoglycoside Antibacterial. Tobramycin is also sold under the brand name Bethkis. Tobramycin is taken by mouth, whereas Penicillin G is given by intravenous (IV) infusion. Tobramycin additionally carries an FDA boxed warning, the FDA's strongest safety alert.

What the FDA label says

"Aminoglycoside combined with antibiotic that interferes with cell-wall synthesis"

📖 Source: NLP:tobramycin

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Data integrity: Every interaction shown is extracted directly from official U.S. FDA drug labeling via openFDA and the U.S. National Library of Medicine (NIH) — no interactions are invented, inferred, or manually edited. Maintained by CheckDrugInteractions.com. See our methodology or report a correction at support@checkdruginteractions.com.

Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine, supplemented with a small number of well-established interactions from curated clinical references. For informational purposes only. Always consult your pharmacist or physician.