COLLIE-AM POWDER

Indications

• Bacterial infections
• Listerial meningitis
• Bronchitis
• Urinary tract infections
• Community-acquired pneumonia
• Salmonellosis

Dosage

Children: Refer to the BNF for Children for specific dosing: Neonate up to 7 days: 30 mg/kg every 12 hours; Neonate 7 to 20 days: 30 mg/kg every 8 hours; Neonate 21 to 28 days: 30 mg/kg every 6 hours.

Adults: 500 mg to 1 g every 6 hours, depending on the severity of the infection.

Mechanism of action

Ampicillin works by inhibiting bacterial cell wall synthesis, leading to cell lysis and death in susceptible bacteria.

Pharmacodynamics

Ampicillin exhibits bactericidal activity against a broad spectrum of gram-positive and some gram-negative bacteria, including Streptococcus spp., Enterococcus spp., and certain E. coli strains.

Pharmacokinetics

Ampicillin is well absorbed from the gastrointestinal tract, with a bioavailability of approximately 50-70%. It is distributed widely in body tissues and fluids, including the central nervous system. It is primarily eliminated by the kidneys through glomerular filtration and tubular secretion.

Adverse effects

• Colitis haemorrhagic
• Skin rash

Interactions

• Allopurinol (increases risk of skin rash)

Precautions

• Caution in renal impairment
• Potential for electrolyte accumulation with intravenous use

Pregnancy

Not known to be harmful.

Breast-feeding

Trace amounts in milk, but appropriate to use.

Storage

Store in a cool, dry place, protected from light.

Formulations

• Ampicillin 500 mg capsules
• Ampicillin 125 mg/5 ml oral suspension
• Ampicillin 25 mg per 1 ml oral suspension
• Ampicillin powder for injection

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

By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, Ampicillin 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 Ampicillin interferes with an autolysin inhibitor. SINCE PENICILLIN HAS NO EFFECT ON EXISTING CELL WALLS, BACTERIA MUST BE MULTIPLYING FOR BACTERICIDAL ACTION OF PENICILLIN TO BE MANIFEST. /PENICILLINS/ 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 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

Ampicillin 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. Ampicillin has <i>in vitro</i> activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of Ampicillin results from the inhibition of cell wall synthesis and is mediated through Ampicillin binding to penicillin binding proteins (PBPs). Ampicillin is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, and cephalosporinases and extended spectrum beta-lactamases.

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.