Penicillin is a group of antibiotics which include penicillin G, penicillin V, procaine penicillin, and benzathine penicillin.
Penicillin inhibits activity of enzymes that are needed for the cross linking of peptidoglycans in bacterial cell walls, which is the final step in cell wall biosynthesis.
Bacteria constantly remodel their peptidoglycan cell walls.
Bacteria simultaneously building and breaking down portions of the cell wall as they grow and divide.
Penicillin acts by inhibiting penicillin-binding proteins, which normally catalyze cross-linking of bacterial cell walls.
This results in cell wall weakening due to fewer cross links and water uncontrollably flows into the cell because it cannot maintain the correct osmotic gradient.
Bacteria that attempt to grow and divide in the presence of penicillin fail to do so, and end up shedding their cell walls.
This results in cell lysis and death.
Penicillin G is for intravenous use.
Penicillin V is oral
Procaine and benzathine Penicillin are intramuscular agents.
Among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci.
Pregnancy category US: B (No risk in non-human studies)
Routes of administration Intravenous, intramuscular, oral.
Metabolism- liver
Elimination half-life between 0.5 and 56 hours.
Excretion by Kidneys
About 10% of people report an allergy to penicillin; however, up to 90% of this group may not actually be allergic.
Serious PCN allergies only occur in about 0.03%.
All penicillins are β-lactam antibiotics.
Penicillin families effective against additional bacteria; these include the antistaphylococcal penicillins, aminopenicillins and the antipseudomonal penicillins.
Penicillins are derived from Penicillium fungi.
Procaine penicillin and benzathine penicillin have the same antibacterial activity as benzylpenicillin but act for a longer period of time.
Phenoxymethylpenicillin is less active against gram-negative bacteria than benzylpenicillin.
Benzylpenicillin, procaine penicillin and benzathine penicillin can only be given by intravenous or intramuscular injections.
Phenoxymethylpenicillin can be given by mouth because of its acidic stability.
The range of infections caused by susceptible bacteria include: Streptococcus, Staphylococcus, Clostridium, Neisseria, and Listeria genera.
Adverse drug reactions:
Common with ≥ 1% of people-diarrhea, hypersensitivity, nausea, rash, neurotoxicity, urticaria, and superinfection.
Infrequent adverse effects affecting 0.1–1% of people include:
fever, vomiting, erythema, dermatitis, angioedema, seizures, and pseudomembranous colitis.
PCN can induce serum sickness or a serum sickness-like reaction in some individuals.
Allergy will occur in 1-10% of people, presenting as a skin rash after exposure.
IgE-mediated anaphylaxis will occur in approximately 0.01% of patients.
Pain and inflammation at the injection site are also common for parenteral benzathine benzylpenicillin, benzylpenicillin, and, to a lesser extent, procaine benzylpenicillin.
Penicillin G, administered as benzylpenicillin IV or IM.
Penicillin G has high urinary excretion and is produced as a salt of potassium or sodium.
Penicillin V, phenoxymethylpenicillin orally is less active than benzylpenicillin against Gram-negative bacteria.
Benzathine benzylpenicillin, benzathine penicillin G, intramuscularly causes slower release over two to four weeks.
Procaine benzylpenicillin, penicillin G procaine has slow release intramuscularly.
Some bacteria produce enzymes that break down the beta-lactam ring, called beta-lactamases
Bacteria that make beta-lactam enzymes make the bacteria resistant to penicillin.
Beta lactamase inhibitors irreversibly bind to beta-lactamase preventing it breaking down on beta lactam rings on the antibiotic molecule.
The use of clavulanic acid or tazobactam, beta-lactamase inhibitors, with penicillin gives penicillin activity against beta-lactamase producing bacteria.
β-Lactam antibiotics inhibit the formation of peptidoglycan cross-links in the bacterial cell wall.
β-Lactam antibiotics bind the four-membered β-lactam ring of penicillin to the enzyme DD-transpeptidase.
Subsequently, DD-transpeptidase cannot catalyze formation of these cross-links, and an imbalance between cell wall production and degradation develops, causing the cell to die.
Protoplasts are Gram-positive bacteria when they lose their cell walls.
Gram-negative bacteria do not lose their cell walls completely after treatment with penicillin, and are called spheroplasts.
Penicillin have a synergistic effect with aminoglycosides, since the inhibition of peptidoglycan synthesis allows aminoglycosides to penetrate the bacterial cell wall more easily.
Some bacteria produce enzymes that break down the beta-lactam ring, called beta-lactamases.
Beta-lactamases make the bacteria resistant to penicillin.
Therefore, some penicillins are modified or given with other drugs for use against antibiotic resistant bacteria or in immunocompromised patients.
Penicillin has low protein binding in plasma.
Penicillin G has a low bioavailability, below 30%.
Penicillin V has a bioavailability between 60 and 70%.
Penicillin has a biological short half life and is excreted via the kidneys.
The key structural feature of the penicillins is the four-membered β-lactam ring, essential for penicillin’s antibacterial activity.
It is actively excreted, and about 80% of a penicillin dose is cleared from the body within three to four hours of administration.
When probenecid and penicillin are administered together, probenecid competitively inhibits the excretion of penicillin.
The combination of probenecid and penicillin increases penicillin’s concentration and prolongs its activity.
Ampicillin offered a broader spectrum of activity than either of the original penicillins.
β-lactamase-resistant penicillins, including flucloxacillin, dicloxacillin, and methicillin have significant activity against β-lactamase-producing bacterial species, but were ineffective against the methicillin-resistant Staphylococcus aureus (MRSA) strains that subsequently emerged.
Antipseudomonal penicillins, such as carbenicillin, ticarcillin, and piperacillin, are useful for their activity against Gram-negative bacteria.
The β-lactam ring is retained it at the center of the structures of mecillinams, carbapenems and, the cephalosporins.
Penicillin is a metabolite of certain species of Penicillium and is produced when growth of the fungus is inhibited by stress.
Pregnancy category US: B (No risk in non-human studies)
Routes of administration Intravenous, intramuscular, by mouth
Metabolism by the liver.
Elimination half-life between 0.5 and 56 hours. Excretion by Kidneys.
About 10% of people report that they are allergic to penicillin; however, up to 90% of this group may not actually be allergic.
Serious PCN allergies only occur in about 0.03%.
Those allergic to penicillin are most often given cephalosporin because of its functional groups.
Procaine penicillin and benzathine penicillin have the same antibacterial activity as benzylpenicillin but act for a longer period of time.
Phenoxymethylpenicillin is less active against gram-negative bacteria than benzylpenicillin.
Benzylpenicillin, procaine penicillin and benzathine penicillin can only be given by intravenous or intramuscular injections, but phenoxymethylpenicillin can be given by mouth because of its acidic stability.
The number of penicillin-resistant bacteria is increasing.
Susceptible bacteria include: those in the Streptococcus, Staphylococcus, Clostridium, Neisseria, and Listeria genera.
Side effects of penicillin: Common (≥ 1% of people) adverse drug reactions include diarrhea, hypersensitivity, nausea, rash, neurotoxicity, urticaria, and superinfection.
Infrequent adverse effects (0.1–1% of people) include fever, vomiting, erythema, dermatitis, angioedema, seizures and pseudomembranous colitis.
Pain and inflammation at the injection site are common for parenterally administered benzathine benzylpenicillin, benzylpenicillin, and, to a lesser extent, procaine benzylpenicillin.