Penicillin G Sodium

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Cat Number

API0231579

CAS Number

69-57-8

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Product Detail Description Scientific Support Customer Q&A

CAS Number

69-57-8

EINECS

200-710-2

Storage

Store at 2-8℃

Synonyms

Crystapen; Benzylpenicillin sodium; BENZYLPENICILLIN SODIUM SALT; American penicillin; Sodium penicillin G

Molecular Formula

C16H17N2NaO4S

Molecular Weight

356.4

Smiles

CC1([C@@H](N2[C@H](S1)[C@@H](C2=O)NC(=O)CC3=CC=CC=C3)C(=O)[O-])C.[Na+]

Appearance

White to slightly yellow crystalline powder

Melting Point

209-212℃

Boiling Point

663.3℃

Relative Density

1.41

General Description

Penicillin G sodium is a natural, parenteral beta-lactam antibiotic derived from Penicillium chrysogenum and represents the original member of the penicillin family. It is available as a crystalline powder for reconstitution and intravenous or intramuscular administration. The drug is acid-labile and therefore ineffective orally, necessitating injectable delivery for systemic effect.

Mechanism of Action

Penicillin G exerts bactericidal activity by binding to penicillin-binding proteins (PBPs) located on the bacterial cell wall. This binding inhibits transpeptidase enzymes responsible for cross-linking peptidoglycan strands, disrupting cell wall synthesis. The resultant loss of structural integrity leads to osmotic lysis, particularly during active bacterial replication. The drug is most effective against gram-positive organisms and certain spirochetes.

Application

This antibiotic remains the drug of choice for infections caused by non-resistant streptococci, Treponema pallidum (syphilis), Clostridium perfringens, and Neisseria meningitidis. It is also used for pneumococcal pneumonia and endocarditis due to penicillin-susceptible strains. High doses are required for central nervous system infections due to limited penetration, and resistance mediated by beta-lactamase is increasingly encountered.

In this multicenter, randomized, noninferiority trial (249 participants, 61% HIV‑positive), patients with early syphilis received either one or three weekly doses of intramuscular benzathine penicillin G (2.4 million units each). The primary endpoint—serologic response (≥4‑fold RPR titer drop or seroreversion) at 6 months—was achieved in 76% of the single‑dose group versus 70% of the three‑dose group (difference –6 percentage points; noninferiority margin 10%). No clinical relapses occurred. A single dose is noninferior to three doses for early syphilis, regardless of HIV status, supporting simplified treatment.

Fig. 1 Serological Response to Benzathine Penicillin (95% CI) Therapy Stratified by Stage and Treatment Group. (Hook EW 3rd, et al., 2025)

References

Hook EW 3rd, et al. One Dose versus Three Doses of Benzathine Penicillin G in Early Syphilis. N Engl J Med. 2025;393(9):869-878.

Does Penicillin G Sodium require refrigerated storage as a beta-lactam antibiotic?

Yes, it must be stored at 2-8°C. At room temperature, rapid hydrolysis of the beta-lactam ring occurs, leading to significant potency loss.

Is Penicillin G Sodium extremely moisture-sensitive, and how is this prevented?

Yes, it is highly hygroscopic. Our packaging includes moisture-barrier vials or foil bags with desiccant, and the material should be opened only in low-humidity environments.

What is the stability of Penicillin G Sodium after reconstitution for injection?

Reconstituted solutions have limited stability (typically 24-48 hours under refrigeration). We provide detailed in-use stability data for various diluents and storage conditions.

How is the impurity penicilloic acid monitored during stability?

This primary hydrolysis product is specifically quantified using a stability-indicating HPLC method, ensuring it remains below pharmacopoeial limits.