What is the Difference Between Penicillin G and Penicillin V

The main difference between penicillin G and penicillin V is that penicillin G is formed when phenylacetic acid is added to the culture medium whereas penicillin V is formed when phenoxyacetic acid is added to the medium.

Penicillin G and V are two of the first-generation penicillins that are important to treat bacterial infections.  

Key Areas Covered

1. What is Penicillin G
– Definition, Structure, Function
2. What is Penicillin V
– Definition, Structure, Function
3. Similarities Between Penicillin G and Penicillin V
– Outline of Common Features
4. Difference Between Penicillin G and Penicillin V
– Comparison of Key Differences

Key Terms

Benzylpenicillin, Penicillin, Penicillin G, Penicillin V, Phenoxymethylpenicillin 

What is Penicillin G

Penicillin G or Benzylpenicillin is a beta-lactam antibiotic important for treating bacterial infections. It is also a broad-spectrum antibiotic that treats pneumonia, strep throat, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospirosis, cellulitis, and tetanus. In addition, it is given as an injection to veins or muscles. There are two long-acting forms of the drug: benzathine benzylpenicillin and procaine benzylpenicillin. They are given as an injection into a muscle. Apart from that, the side effects of penicillin G include diarrhea, seizures, and allergic reactions including anaphylaxis.

Figure 1: Penicillin G

Furthermore, penicillin G is effective against Gram-positive bacteria. Some Gram-negative organisms are susceptible to penicillin G. Generally, penicillin G binds to penicillin-binding proteins (PBPs) inside of the bacterial cell wall and inactivates them. However, the inactivation of the PBPs interferes with the cross-linkage of the peptidoglycan chains that are important for the rigidity and strength of the bacterial cell wall, interrupting cell wall synthesis. Eventually, this results in the weakening of the bacterial cell wall, causing cell lysis.

What is Penicillin V

Penicillin V or Phenoxymethylpenicillin is an important broad-spectrum antibiotic of the beta-lactam family. In general, it treats a number of bacterial infections, especially, strep throat, otitis media, and cellulitis. It is also helpful in preventing rheumatic fever. The administration route of penicillin V is by mouth. The side effects of penicillin V include diarrhea, nausea, and allergic reactions including anaphylaxis.

Figure 2: Penicillin V

Moreover, penicillin V is an antibiotic that causes the death of bacteria by weakening their cell walls. Therefore, it is active against Gram-positive bacteria and less active against Gram-negative bacteria. However, penicillin V is more acid tolerant in comparison to penicillin G, and therefore, it is given orally. Since the absorption of penicillin V is unpredictable, it is given for mild to moderate infections but not for severe infections. 

Similarities Between Penicillin G and Penicillin V

• Penicillin G and penicillin V are two penicillin antibiotics, natural penicillins.
• Both are broad-spectrum antibiotics that are in the beta-lactam family. They cause bacteria to die.
• They are active against Gram-positive bacteria and less active against Gram-negative bacteria.
• Moreover, they have similar side effects.
• Both are not recommended for those who are having a penicillin allergy.

Difference Between Penicillin G and Penicillin V

Definition

Generally, penicillin G refers to a penicillin beta-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms, while penicillin V refers to a member of the penicillin family exhibiting broad-spectrum antibiotic properties.

Production

Penicillin G is formed when phenylacetic acid is added to the culture medium while penicillin V is formed when phenoxyacetic acid is added to the medium.

Molecular Formula

The molecular formula of penicillin G is C₁₆H₁₈N₂O₄S while the molecular formula of penicillin V is C₁₆H₁₈N₂O₅S.

Synonyms

Another name for penicillin G is Benzylpenicillin while the other name for penicillin V is Phenoxymethylpenicillin.

Type of Infections

Penicillin G helps to treat pneumonia, strep throat, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospirosis, cellulitis, and tetanus while penicillin V helps to treat strep throat, otitis media, and cellulitis.

Side Effects

The side effects of penicillin G include diarrhea, seizures, and allergic reactions including anaphylaxis while the side effects of penicillin V include diarrhea, nausea, and allergic reactions including anaphylaxis.

Conclusion

In brief, Penicillin G and penicillin V are two types of broad-spectrum, beta-lactam antibiotics. Both help in weakening bacterial cell walls by binding to the penicillin-binding proteins. Therefore, both types of antibiotics are active against Gram-positive bacteria and less active against Gram-negative bacteria. However, penicillin G is formed with the addition of phenylacetic acid to the culture medium while penicillin V occurs with the addition of phenoxyacetic acid. In addition, penicillin G is important to treat several infections including pneumonia, strep throat, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospirosis, cellulitis, and tetanus while penicillin V is important to treat strep throat, otitis media, and cellulitis. Therefore, the main difference between penicillin G and penicillin V is their production.

References:

1. Ball, A. P., et al. “The Natural Penicillins – Benzylpenicillin (Penicillin G) and Phenoxymethylpenicillin (Penicillin V).” SpringerLink, Springer Netherlands, 1 Jan. 1978, 
2. “Penicillin V.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “Benzylpenicillin” By Vaccinationist – Own work (Public Domain) via Commons Wikimedia
2. “Penicillin-V-2D-skeletal” By Bert.Kilanowski – Own Work (CC0) via Commons Wikimedia