Does Penicillin G Interact with Tobramycin?
Penicillin G and Tobramycin 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 Penicillin G and Tobramycin 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 Penicillin G and your doctor is considering prescribing Tobramycin (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