Penicillins

Question 1

Examples of broad spec penicillins

Answer 1

NOT used in CNS infections except meningitis because poorly penetrate cerebral spinal fluid

Amoxicillin (TDS)

Co-amoxiclav (+clavulanic acid) but causes cholestatic jaundice esp Tx >14 days

Ampicillin (before food - QDS, high resistance)

Question 2

MOA

Answer 2

• Prevents peptidoglycan cross linking in bacterial cell walls (bacteriacidal)
• Broad or narrow spec

Question 3

Examples of narrow spec penicillins

Answer 3

• Benzylpenicillin (parenteral)
• Phenoxymethylpenicillin (QDS)
• Flucoxacillin (staphylococcal infections) (Before food, QDS, cholestatic jaundice, life threatening hypoKalaemia)

Question 4

Examples of antipseudomonal (serious infections)

Answer 4

• Piperacillin (parenteral)
• Ticarcillin (parenteral)

Question 5

What are the indications of amoxicillin?

Answer 5

• RTI
• H pylori
• Otitis media
• Oral infection
• UTI
• NOT sore throats (Sore throats cause grandular fever, rashes are a common symptom - may mistake for penicillin allergy)

Question 6

What is the dose of amoxicillin?

Answer 6

• 1-11M: 125mg TDS
• 1-4Y: 250mg TDS
• Adult: 500-1000mg TDS

Question 7

What are the side effects of amoxicillin?

Answer 7

Antibiotic associated colitis (broad spec)

Penicillin allergy
- True allergy (anaphylaxis, urticaria, immediate rash) - no beta lactam abx
- May not be allergy ( develop minor rash >72H) - penicillin only for serious infections

Question 8

What is the route for amoxicillin?

Answer 8

NOT intrathecal - damage brain

Question 9

What are the interactions of amoxicillin?

Answer 9

Warfarin → bleed

Methotrexate toxicity

Hepatotoxicity (flucox + co-amoxiclav)