ANTIBODY WATER SOLUBLE POWDER

Indications

• Treatment of multidrug-resistant gram-negative bacterial infections
• Pneumonia caused by Pseudomonas aeruginosa
• Complicated urinary tract infections
• Infections in cystic fibrosis patients

Dosage

Children: Refer to the BNF for Children for appropriate paediatric dosing information.

Adults: Refer to the BNF for specific dosing guidelines, as doses may vary based on infection severity and renal function.

Mechanism of action

Colistin interacts with the bacterial cytoplasmic membrane, disrupting its integrity and altering permeability. It binds to the membrane through its cationic properties, leading to leakage of essential intracellular components, which results in bactericidal effects.

Pharmacodynamics

Colistin functions as a cationic polypeptide that disrupts bacterial cell membranes via a detergent-like mechanism. It is effective against certain multidrug-resistant organisms, including Pseudomonas aeruginosa and Acinetobacter baumannii. Its use has increased due to the rise of antibiotic-resistant infections, particularly in patients with cystic fibrosis and other serious infections.

Pharmacokinetics

Colistin is administered parenterally and has variable pharmacokinetics depending on the route of administration. It is not well-absorbed orally and is primarily eliminated by the kidneys. The pharmacokinetic profile may vary based on renal function and dosage regimen, necessitating careful monitoring in patients with renal impairment.

Adverse effects

• Nephrotoxicity
• Neurotoxicity
• Allergic reactions
• Rash
• Fever

Interactions

• Increased risk of nephrotoxicity with other nephrotoxic agents
• Potential interactions with neuromuscular blockers

Precautions

• Monitor renal function during treatment
• Use with caution in patients with renal impairment
• Consider monitoring neuromuscular function in patients receiving concomitant neuromuscular blockers

Pregnancy

Colistin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether colistin is excreted in human milk. Caution should be exercised when administering to a nursing mother.

Storage

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

Formulations

• Colistin sulfate for injection
• Colistin methanesulfonate for injection

Indications

• Bacterial infections
• Respiratory tract infections
• Urinary tract infections
• Skin infections
• Gastrointestinal infections

Dosage

Children: Refer to the BNF for Children for appropriate dosing in paediatric patients.

Adults: Refer to the specific product guidelines for dosing information, as it can vary based on the indication and formulation used.

Mechanism of action

Enrofloxacin exerts its antibacterial effect through the inhibition of bacterial DNA gyrase and topoisomerase IV, which are essential enzymes for DNA replication and transcription. By interfering with these enzymes, enrofloxacin disrupts the normal function of the bacterial cell, leading to cell death.

Pharmacodynamics

Enrofloxacin has a bactericidal effect, meaning it kills bacteria rather than merely inhibiting their growth. Its activity is concentration-dependent, meaning that higher concentrations lead to more significant antibacterial effects. The drug has a broad spectrum of activity against many gram-negative bacteria, including Pseudomonas aeruginosa, as well as some gram-positive organisms.

Pharmacokinetics

Enrofloxacin is well-absorbed after oral administration, with peak plasma concentrations typically achieved within 1 to 2 hours. It is widely distributed throughout the body, including into tissues and fluids, and has good penetration into the central nervous system. The elimination half-life varies but is generally between 4 to 8 hours in humans. Enrofloxacin is primarily metabolized in the liver, and its metabolites, including ciprofloxacin, are also active against bacteria.

Contra-indications

• Hypersensitivity to enrofloxacin or any of its components
• Use in growing animals due to potential effects on cartilage development

Adverse effects

• Gastrointestinal disturbances such as vomiting and diarrhea
• Central nervous system effects including seizures and ataxia
• Tendon rupture or damage, particularly in larger breed dogs
• Possible cartilage damage in young animals

Interactions

• Antacids or products containing aluminum, magnesium, or iron may reduce the absorption of enrofloxacin
• Cationic agents may interfere with its antimicrobial activity
• Concurrent use with other nephrotoxic drugs may increase the risk of renal toxicity

Precautions

• Use with caution in animals with a history of seizures or renal impairment
• Monitor for signs of adverse reactions during therapy
• Not for use in animals with known hypersensitivity to fluoroquinolones

Pregnancy

Safety during pregnancy has not been established, use only if benefits outweigh risks.

Breast-feeding

Safety during lactation has not been fully established, use with caution.

Storage

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

Formulations

• Injectable solution
• Oral tablets
• Oral suspension

Mechanism of action

Colistin is a surface active agent which penetrates into and disrupts the bacterial cell membrane. Colistin is polycationic and has both hydrophobic and lipophilic moieties. It interacts with the bacterial cytoplasmic membrane, changing its permeability. This effect is bactericidal. There is also evidence that polymyxins enter the cell and precipitate cytoplasmic components, primarily ribosomes. POLYMYXIN B IS SURFACE-ACTIVE AGENT... CONTAINING LIPOPHILIC & LIPOPHOBIC GROUPS SEPARATED WITHIN MOLECULE. /POLYMYXIN B/ PERMEABILITY OF THE BACTERIAL MEMBRANE CHANGES IMMEDIATELY ON CONTACT WITH DRUG. SENSITIVITY TO POLYMYXIN B APPARENTLY IS RELATED TO THE PHOSPHOLIPID CONTENT OF THE CELL WALL-MEMBRANE COMPLEX. /POLYMYXIN B/ Colistin acts like a cationic detergent and binds to and damages the bacterial cytoplasmic membrane of susceptible bacteria. Damage to the bacterial cytoplasmic membrane alters the osmotic barrier of the membrane and causes leakage of essential intracellular metabolites and nucleosides.

Pharmacodynamics

Colistin is a polymyxin antibiotic agent. Polymyxins are cationic polypeptides that disrupt the bacterial cell membrane through a detergentlike mechanism. With the development of less toxic agents, such as extended-spectrum penicillins and cephalosporins, parenteral polymyxin use was largely abandoned, except for the treatment of multidrug-resistant pulmonary infections in patients with cystic fibrosis. More recently, however, the emergence of multidrug-resistant gram-negative bacteria, such as <i>Pseudomonas aeruginosa</i> and <i>Acinetobacter baumannii</i>, and the lack of new antimicrobial agents have led to the revived use of the polymyxins.