Penicillins

Question 1

Indications

Answer 1

1. Strep infection including tonsillitis, pneumonia (in combination with a macrolide if severe), endocarditis and soft tissue infections
2. Clostridial infection eg tentanus
3. Meningococcal infection eg meningitis

Question 2

Mechanism of action

Answer 2

Inhibit enzymes that cross-link peptidoglycan in bacterial cell walls

Bacteria resist the penicillins using beta-lactamase. Other mechanisms use reduced absorption or change the enzyme target.

Question 3

Adverse effect

Answer 3

Allergy affects 1-10% of people. Usually presents as a skin rash.

Less commonly anaphylaxis.

Question 4

Warnings

Answer 4

Safe in most situations

Question 5

Interactions

Answer 5

Reduce renal excretion of methotrexate.

Question 6

Prescription

Answer 6

Benzylpenicillin can only be administered by injection (IM/IV) as it is hydrolysed by stomach acid.

Penicillin V can be taken orally but absorption is unpredictable and is less active.

Question 7

Administration

Answer 7

IV benzylpenicillin can be given either as slow IV or infusion.

Question 8

Communication

Answer 8

Explain that the aim of treatment is to get rid of infection and improve symptoms. For oral treatment, encourage the patient to complete the prescribed course.

ALLERGY ALLERGY ALLERGY

Question 9

Monitoring

Answer 9

Inflammatory marker