BENZATHINE 2.4MEGA INJECTION

Indications

• Rheumatic fever prevention
• Syphilis treatment
• Streptococcal infections
• Prophylaxis for bacterial endocarditis

Dosage

Children: Refer to BNF for Children for specific dosing guidelines.

Adults: Refer to BNF for specific dosing guidelines.

Mechanism of action

Benzathine penicillin G works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins within the bacterial cell wall, preventing the cross-linking of peptidoglycan layers, which is essential for maintaining the structural integrity of the bacterial cell wall. This leads to cell lysis and death of the bacteria.

Pharmacodynamics

Benzathine penicillin G exhibits bactericidal activity against a wide range of gram-positive organisms, particularly streptococci and certain strains of staphylococci. Its therapeutic effects are largely due to its ability to maintain therapeutic levels in the body for an extended period, allowing for once-monthly dosing in many cases. The efficacy can be influenced by the site of infection and the susceptibility of the bacteria.

Pharmacokinetics

After intramuscular injection, benzathine penicillin G is slowly released into the bloodstream, resulting in sustained serum levels over time. Its half-life can vary but is generally around 3 to 4 weeks, depending on the dosage and individual patient factors. The drug is primarily excreted by the kidneys, and its pharmacokinetics may be altered in patients with renal impairment.

Contra-indications

• Hypersensitivity to benzathine or any of its components
• History of severe allergic reactions to penicillin
• Active infections caused by penicillin-resistant organisms

Adverse effects

• Allergic reactions including anaphylaxis
• Local injection site reactions such as pain, swelling, and inflammation
• Fever
• Nausea
• Diarrhea
• Dizziness

Interactions

• May interact with other antibiotics, particularly those that are also beta-lactam antibiotics
• Potential for increased risk of bleeding when used with anticoagulants

Precautions

• Use with caution in patients with a history of asthma or allergies
• Monitor patients for signs of anaphylaxis after administration
• Consider alternative therapy in patients with renal impairment

Pregnancy

Benzathine is generally considered safe for use during pregnancy, but should be used only if clearly needed.

Breast-feeding

Benzathine is excreted in breast milk; however, it is not expected to harm a nursing infant when used at therapeutic doses.

Storage

Store at room temperature, away from light and moisture. Do not freeze.

Formulations

• Benzathine benzylpenicillin injection
• Benzathine benzylpenicillin for intramuscular use

Indications

• Bacterial infections
• Pneumonia
• Streptococcal infections
• Syphilis
• Meningitis
• Endocarditis
• Skin infections

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations based on the type of penicillin and indication.

Adults: Refer to the BNF for specific dosing recommendations based on the type of penicillin and indication.

Mechanism of action

Penicillin targets penicillin-binding proteins (PBPs) located inside the bacterial cell wall. By binding to these proteins, penicillin disrupts the transpeptidation process, which is essential for cell wall structural integrity. This results in weakened cell walls, causing osmotic instability and ultimately leading to cell lysis and death.

Pharmacodynamics

Penicillin exhibits bactericidal activity, meaning that it kills bacteria rather than merely inhibiting their growth. Its effectiveness is generally dependent on the growth phase of the bacteria, as it is most active against actively dividing cells. The spectrum of activity varies among different penicillins, with some being more effective against specific bacterial strains.

Pharmacokinetics

Penicillin is primarily absorbed in the gastrointestinal tract, with its bioavailability varying depending on the specific type of penicillin. It is primarily excreted by the kidneys, with a half-life that typically ranges from 30 minutes to 2 hours, depending on the formulation. Dosage adjustments may be necessary in patients with renal impairment to prevent accumulation and toxicity.

Contra-indications

• History of hypersensitivity to penicillins
• Severe allergic reactions to beta-lactam antibiotics

Adverse effects

• Allergic reactions such as rash, urticaria, and anaphylaxis
• Gastrointestinal disturbances including nausea, vomiting, and diarrhea
• Superinfection due to alteration of normal flora
• Hematologic reactions such as leukopenia, thrombocytopenia

Interactions

• valproate+penicillins: Severe (increases risk of adverse effects)
• allopurinol+penicillins: Unknown (increases risk of skin rash)
• leflunomide+penicillins: Unknown (increases exposure)
• nitisinone+penicillins: Unknown (increases exposure)
• penicillins+phenindione: Unknown (increases risk of bleeding events)
• teriflunomide+penicillins: Unknown (increases exposure)

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of allergic reactions
• Consider alternative therapy in patients with a history of severe allergies

Pregnancy

Penicillins are generally considered safe to use during pregnancy; however, consult local guidelines and assess benefits versus risks.

Breast-feeding

Penicillins are excreted in breast milk in small amounts; generally considered safe, but monitor infant for possible effects.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Oral tablets
• Oral suspension
• Intravenous injection
• Intramuscular injection