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Penicillin G (Penicillin G Potassium) - Drug Interactions, Contraindications, Overdosage, etc



Drug Interactions

Bacteriostatic antibacterials (i.e., chloramphenicol, erythromycins, sulfonamides or tetracyclines) may antagonize the bactericidal effect of penicillin, and concurrent use of these drugs should be avoided. This has been documented in vitro, however, the clinical significance of this interaction is not well-documented.

Penicillin blood levels may be prolonged by concurrent administration of probenecid which blocks the renal tubular secretion of penicillins. Other drugs may compete with penicillin G for renal tubular secretion and thus prolong the serum half-life of penicillin. These drugs include: aspirin, phenylbutazone, sulfonamides, indomethacin, thiazide diuretics, furosemide and ethacrynic acid.


Dose related toxicity may arise with the use of massive doses of intravenous penicillins (40 to 100 million units per day), particularly in patients with severe renal impairment (see PRECAUTIONS). The manifestations may include agitation, confusion, asterixis, hallucinations, stupor, coma, multifocal myoclonus, seizures and encephalopathy. Hyperkalemia is also possible (see ADVERSE REACTIONS, Metabolic).

In case of overdosage, discontinue penicillin, treat symptomatically and institute supportive measures as required. If necessary, hemodialysis may be used to reduce blood levels of penicillin G, although the degree of effectiveness of this procedure is questionable.


A history of a hypersensitivity (anaphylactic) reaction to any penicillin is a contraindication.


1. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard – Ninth Edition, CLSI document M07-A9. Clinical and Laboratory Standards Institute. Wayne, PA. January, 2012.

2. Performance Standards for Antimicrobial Susceptibility Testing, Twenty-Second Informational Supplement, CLSI document M100-S22. Clinical and Laboratory Standards Institute. Wayne, PA. January, 2012.

3. Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard – Eleventh Edition, CLSI document M02-A11. Clinical and Laboratory Standards Institute. Wayne, PA. January, 2012.

4. Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria; Approved Guideline-Second Edition, CLSI document M45-A2. Clinical and Laboratory Standards Institute. Wayne, PA. August, 2010.

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Manufactured for:

WG Critical Care, LLC

Paramus, NJ 07652


INS15862 03


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