PENICILLIN G SODIUM INJECTION 1M.U

Indications

• Bacterial infections caused by susceptible organisms
• Pneumonia
• Meningitis
• Endocarditis
• Sepsis
• Skin and soft tissue infections
• Bone and joint infections

Dosage

Children: Refer to the BNF

Adults: Refer to the BNF for specific dosing guidelines based on the type and severity of infection.

Mechanism of action

Benzylpenicillin exerts its bactericidal effect by binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall. This binding inhibits the third and final stage of bacterial cell wall synthesis. The weakened cell wall ultimately leads to cell lysis, which is mediated by bacterial autolytic enzymes. The action of benzylpenicillin is dependent on its ability to reach and bind to these PBPs, which include transpeptidases, carboxypeptidases, and endopeptidases.

Pharmacodynamics

Benzylpenicillin is particularly effective against gram-positive bacteria and has activity against some gram-negative organisms as well. Its bactericidal nature is attributed to the inhibition of cell wall synthesis, which disrupts the structural integrity of the bacterial cell. Benzylpenicillin remains stable against hydrolysis by various beta-lactamases, including penicillinases and extended-spectrum beta-lactamases, enhancing its efficacy in treating infections caused by resistant strains.

Pharmacokinetics

Benzylpenicillin is administered via parenteral routes due to its poor oral bioavailability. It is widely distributed throughout the body, including the central nervous system, especially in the presence of inflammation. The drug is primarily eliminated by the kidneys through glomerular filtration and tubular secretion, with a half-life of approximately 30 minutes to 1 hour in healthy adults. Dosing may need adjustment in patients with renal impairment.

Contra-indications

• Hypersensitivity to benzylpenicillin or any other penicillins
• History of severe allergic reactions to beta-lactam antibiotics

Adverse effects

• Allergic reactions including rash, pruritus, and anaphylaxis
• Gastrointestinal disturbances such as nausea, vomiting, and diarrhea
• Hematologic effects including leukopenia, thrombocytopenia, and hemolytic anemia
• Renal toxicity in cases of high doses or prolonged use

Interactions

• leflunomide+benzylpenicillin: Unknown (increases exposure)
• nitisinone+benzylpenicillin: Unknown (increases exposure)
• teriflunomide+benzylpenicillin: Unknown (increases exposure)

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of anaphylaxis during initial doses
• Consider alternative therapy in patients with a history of severe penicillin allergy

Pregnancy

Benzylpenicillin is generally considered safe to use during pregnancy, but it should be used only if clearly needed.

Breast-feeding

Benzylpenicillin is excreted in breast milk in small amounts and is considered safe for use during breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight. Reconstituted solutions should be used promptly or stored in a refrigerator and used within 24 hours.

Formulations

• Benzylpenicillin sodium
• Benzylpenicillin potassium

Indications

• Mild to moderate susceptible infections
• Throat infections
• Otitis media
• Cellulitis
• Pneumonia
• Meningitis
• Meningococcal disease
• Endocarditis (in combination with other antibacterials)

Dosage

Children: For children weighing up to 40 kg: 80 mg/kg every 8 hours, increased if necessary to 80 mg/kg every 6 hours for more severe infections. For children weighing 40 kg and above: 3.2 g every 6-8 hours, increased if necessary. Neonates (up to 7 days): 25 mg/kg every 12 hours, increased if necessary to 25 mg/kg every 8 hours. Neonates (7 to 28 days): 25 mg/kg every 8 hours, increased if necessary to 50 mg/kg every 8 hours for severe infections.

Adults: For adults, the usual dose is 3.2 g every 6 hours for severe infections; for less severe infections, 1.2 g every 6 hours may be sufficient. Dosing frequency can be adjusted based on the severity of the infection.

Mechanism of action

Benzylpenicillin sodium inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis and death in susceptible bacteria.

Pharmacodynamics

Benzylpenicillin sodium demonstrates bactericidal activity against Gram-positive bacteria and some Gram-negative bacteria. Its efficacy is influenced by the bacterial growth phase, with maximum activity observed during active cell division.

Pharmacokinetics

Benzylpenicillin sodium is administered via intramuscular or intravenous routes. It has a short half-life, requiring frequent dosing. The drug is primarily eliminated by renal excretion, necessitating dose adjustments in patients with renal impairment.

Adverse effects

• Eosinophilia
• Hypokalaemia
• Thrombophlebitis
• Cholestatic jaundice

Precautions

• High doses may lead to hypernatraemia due to sodium content.
• Caution in hepatic impairment.
• Caution in renal impairment; adjustment needed based on estimated glomerular filtration rate.

Pregnancy

Not known to be harmful.

Breast-feeding

Trace amounts in milk, but appropriate to use.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• Intramuscular injection
• Slow intravenous injection
• Intravenous infusion

Mechanism of action

By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, penicillin G inhibits the third and last stage of bacterial cell wall synthesis. Cell lysis is then mediated by bacterial cell wall autolytic enzymes such as autolysins; it is possible that penicillin G interferes with an autolysin inhibitor. The penicillins and their metabolites are potent immunogens because of their ability to combine with proteins and act as haptens for acute antibody-mediated reactions. The most frequent (about 95 percent) or "major" determinant of penicillin allergy is the penicilloyl determinant produced by opening the beta-lactam ring of the penicillin. This allows linkage of the penicillin to protein at the amide group. "Minor" determinants (less frequent) are the other metabolites formed, including native penicillin and penicilloic acids. /Penicillins/ Bactericidal; inhibit bacterial cell wall synthesis. Action is dependent on the ability of penicillins to reach and bind penicillin-binding proteins (PBPs) located on the inner membrane of the bacterial cell wall. Penicillin-binding proteins (which include transpeptidases, carboxypeptidases, and endopeptidases) are enzymes that are involved in the terminal stages of assembling the bacterial cell wall and in reshaping the cell wall during growth and division. Penicillins bind to, and inactivate, penicillin-binding proteins, resulting in the weakening of the bacterial cell wall and lysis. /Penicillins/

Pharmacodynamics

Penicillin G is a penicillin beta-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms. The name "penicillin" can either refer to several variants of penicillin available, or to the group of antibiotics derived from the penicillins. Penicillin G has <i>in vitro</i> activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of penicillin G results from the inhibition of cell wall synthesis and is mediated through penicillin G binding to penicillin binding proteins (PBPs). Penicillin G is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, and cephalosporinases and extended spectrum beta-lactamases.