COLIMOX WATER SOLUBLE POWDER

Indications

• Bacterial infections
• Urinary tract infections
• Sinusitis
• Uncomplicated community-acquired pneumonia
• Salmonellosis
• Oral infections
• Lyme disease (under expert supervision)
• Acute exacerbation of bronchiectasis
• Anthrax (treatment and post-exposure prophylaxis)

Dosage

Children: 1 month–11 years: 30 mg/kg 3 times a day for 21 days; children 1–4 years: 250 mg 3 times a day; children 5–11 years: 500 mg 3 times a day.

Adults: 500 mg 3 times a day; increased if necessary up to 1 g 3 times a day in severe infections.

Mechanism of action

Amoxicillin works by inhibiting bacterial cell wall synthesis, leading to cell lysis and death. It binds to penicillin-binding proteins (PBPs) located inside the bacterial cell wall, interfering with the transpeptidation process necessary for cell wall integrity.

Pharmacodynamics

Amoxicillin exhibits bactericidal activity against susceptible bacteria. Its action is time-dependent, meaning that its effectiveness is related to the duration of time that the drug concentration remains above the minimum inhibitory concentration (MIC) for the target pathogen.

Pharmacokinetics

Amoxicillin is well absorbed from the gastrointestinal tract, with peak plasma concentrations achieved within 1-2 hours after oral administration. It is widely distributed in body tissues and fluids, and it is excreted primarily via the kidneys. The elimination half-life is approximately 1 hour, and renal impairment may necessitate dosage adjustments.

Adverse effects

• Skin rash
• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Allergic reactions (including anaphylaxis)
• Superinfection (due to resistant organisms)

Interactions

• Allopurinol (increases risk of skin rash)

Precautions

• History of penicillin allergy
• Renal impairment (reduce dose)
• Use with caution in patients with mononucleosis

Pregnancy

Use only if clearly needed; no adequate studies in pregnant women.

Breast-feeding

Amoxicillin is excreted in breast milk; use with caution.

Storage

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

Formulations

• Phenoxymethylpenicillin 250mg/5ml oral solution
• Phenoxymethylpenicillin 250 mg tablets

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

Mechanism of action

Amoxicillin competitively inhibits penicillin-binding protein 1 and other high molecular weight penicillin binding proteins. Penicillin bind proteins are responsible for glycosyltransferase and transpeptidase reactions that lead to cross-linking of D-alanine and D-aspartic acid in bacterial cell walls. Without the action of penicillin binding proteins, bacteria upregulate autolytic enzymes and are unable to build and repair the cell wall, leading to bacteriocidal action. 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/ Amoxicillin is similar to penicillin in its bactericidal action against susceptible bacteria during the stage of active multiplication. It acts through the inhibition of cell wall biosynthesis that leads to the death of the bacteria.

Pharmacodynamics

Amoxicillin competitively inhibit penicillin binding proteins, leading to upregulation of autolytic enzymes and inhibition of cell wall synthesis. Amoxicillin has a long duration of action as it is usually given twice daily. Amoxicillin has a wide therapeutic range as mild overdoses are not associated with significant toxicity. Patients should be counselled regarding the risk of anaphylaxis, _Clostridium difficile_ infections, and bacterial resistance.

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.