Penicillin

Question 1

What type of penicillins are benzylpenicillin and phenoxymethylpenicillin?

Answer 1

narrow antimicrobial spectrum - against some gram(+) and gram(-) cocci

NOT active against gram(+) and gram(-) bacilli

therefore often combined with other antibiotics

Question 2

MOA of benzylpenicillin and phenoxymethylpenicillin?

Answer 2

SUMMARY: Interfere cell wall peptidoglycan cross-linking, this reduces osmotic control resulting in cell lysis (ultimately death).

Penicillins contain a β-lactam ring, which is responsible for their bactericidal activity.

1. Penicillin inhibits the enzymes responsible for cross-linking peptidoglycans in bacterial cell walls.
2. weakens cell walls = uncontrolled entry of water into bacteria = cell swelling, lysis and death.

Question 3

indications for benzylpenicillin and phenoxymethylpenicillin?

Answer 3

1) Streptococcal infections:
- tonsillitis
- pneumonia (w/macrolide or tetracycline)
- endocarditis (gentamicin)
- skin and soft tissue infection (w/flucloxacillin)

2) Meningococcal infection: meningitis, septicaemia.
3) Clostridial infection: gas gangrene (clostridial myonecrosis).

Question 4

Adverse effects of benzylpenicillin and phenoxymethylpenicillin?

Answer 4

1) penicillin allergy - skin rash or anaphylactoid reaction

2) at very high doses - neurological toxicity (coma and convulsions)

Question 5

Contraindications of benzylpenicillin and phenoxymethylpenicillin?

Answer 5

Penicillin allergy

Question 6

Cautions for benzylpenicillin and phenoxymethylpenicillin?

Answer 6

Renal impairment

Question 7

interactions for benzylpenicillin and phenoxymethylpenicillin?

Answer 7

Methotrexate

Question 8

What is a common interaction for benzylpenicillin/ phenoxymethylpenicillin, flucloxacillin and piperacilin?

Answer 8

Methotrexate