INFECTIONS: PENICILLIN, ANTIPSEUDOMONAL

Question 1

PENICILLINS, ASM: INDICATIONS

Answer 1

• Reserved for severe infections particularly where there is a broad spectrum of potential pathogens (inc Pseudomonas Aeruginosa); antibiotic resistance is likely (eg. hospital-acquired infection); or patients are immunocompromised (eg. neutropenia)
• Clinical Infections with these drugs include:

O LRTI
O UTI
O Intra-abdominal sepsis
O Skin and soft tissue infection

Question 2

PENICILLINS, ASM: MOA

Answer 2

• Penicillins inhibit the enzymes responsible for cross-linking peptidoglycans in bacterial cell walls
• This weakens cell walls, preventing them from maintaining an osmotic gradient
• Uncontrolled entry of water into bacteria causes cell swelling, lysis and death
• Penicillins contain a β-lactam ring, which is responsible for their antimicrobial activity
• Side chains attached to the β-lactam ring can be modified to make semi-synthetic penicillins
• For piperacillin, the side chain of broad-spectrum penicillins has been converted to a form of urea
• This longer side chain may improve affinity to penicillin binding proteins, increasing the spectrum of antimicrobial activity to include Pseudomonas aeruginosa
• Addition of the β-lactamase inhibitor tazobactam confers antimicrobial activity against β-lactamaseproducing bacteria (e.g. Staphylococcus aureus, Gram-negative anaerobes)

Question 3

PENICILLINS, ASM: ADVERSE EFFECTS

Answer 3

• GI upset
• AB-associated colitis
• Hypersensitivity

Question 4

PENICILLINS, ASM: WARNINGS

Answer 4

• Antipseudomonal penicillins should be used with caution in people at risk of C. difficile infection, particularly those in hospital and the elderly
• The main contraindication is a history of penicillin allergy. Note that allergy to one type of penicillin implies allergy to all types as it is due to a reaction to the basic penicillin structure
• The dose of antipseudomonal penicillins should be reduced in patients with moderate/severe renal impairment.

Question 5

PENICILLINS, ASM: INTERACTIONS

Answer 5

• MTX

- Can enhance the anticoagulant effect of Warfarin (by killing normal GI flora that synthesis Vit K)

Question 6

PENICILLINS, ASM: EXAMPLES

Answer 6

• piperacillin with tazobactam (e.g. Tazocin®)