Heparin
Contraindicated
Textbook
Incompatibility and potential loss of drug effect.
Do not mix in the same syringe/infusion bottle.
Source: KDT 7e · p58
Drug reference
penicillin
Drug monograph
CDSCO approved
EXCRETION
—
not curated
INTERACTIONS
3 major
incl. contraindicated
PREGNANCY
—
not curated
Top interactionssee all 9 →
- HeparinContraindicatedTextbookKDT 7e · p58
- ChloramphenicolSevereTextbookKDT 7e · p699
- TetracyclineSevereTextbookKDT 7e · p699
Mechanism
Not yet extracted
Indications
Moderate/severe leptospirosis
Dosing
- Adult
- Standard dose
Pharmacokinetics
Half-life
Penicillin-G has a half-life of 30 min.
Excretion
Penicillin is actively secreted into the renal tubules via organic acid transport (OATP).
Drug interactions
Chloramphenicol
Severe
Textbook
Apparent antagonism on pneumococci; higher mortality in pneumococcal meningitis compared to penicillin alone.
Avoid combination for highly sensitive organisms where cidal drug alone is sufficient.
Source: KDT 7e · p699
Tetracycline
Severe
Textbook
Apparent antagonism on pneumococci; higher mortality in pneumococcal meningitis compared to penicillin alone.
Avoid combination for highly sensitive organisms where cidal drug alone is sufficient.
Source: KDT 7e · p699
Erythromycin
Moderate
Textbook
Antagonism for group A Streptococci.
Source: KDT 7e · p699
Gentamicin
Moderate
Textbook
Synergism for enterococcal subacute bacterial endocarditis (SABE), leading to faster cure and reduced chances of relapse.
Source: KDT 7e · p698
Streptomycin
Moderate
Textbook
Synergism for enterococcal subacute bacterial endocarditis (SABE), leading to faster cure and reduced chances of relapse.
Source: KDT 7e · p698
Sulfonamide
Moderate
Textbook
Synergism for actinomycosis.
Source: KDT 7e · p699
Methotrexate
Moderate
Database
Delayed MTX elimination, toxicity
Monitor MTX levels and renal function.
Probenecid
Mild
Textbook-cited
Prolonged antibiotic duration of action and higher blood levels
Intentionally utilized in single-dose gonorrhoea therapy; generally desirable
Source: KDT 7e · p948
Related guidelines
Other Unclassified drugs
Ask House about penicillin
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Sources: KD Tripathi 7e, Harrison 22e·Verified: 2026-05-10 · House clinical team