Macrolides

Question 1

Name three common macrolide antibiotics?

Answer 1

Erythromycin, Clarythromycin and Azithromycin

Question 2

What part of a bacterial cell do macrolide antibiotics target?

Answer 2

Protein Synthesis

Question 3

How do macrolide work?

Answer 3

They bind to the 50s subunit on a bacterial ribosome.
This prevents translocation a process required for the amino acid chain elongation.
This inhibition of protein synthesis has a BACTERIOSTATIC effect allowing the body to then kill and eliminate the bacteria

Question 4

What spectrum do macrolide Abxs have?

Answer 4

Realtively brod spec against Gram + and some Gram -

Clarythromycin is a second generation macrolide so has more activity against Gram - bacteria epically H.Influenza

Question 5

Is bacterial resistance against macrolide common and if so how?

Answer 5

Yes due to ribosomal mutations preventing macrolide binding

Question 6

What are the common uses for macrolide?

Answer 6

1. Respiratory and Skin and Soft tissue infections (when penicillin allergy so is contraindicated)
2. Severe and atypical pneumonia (along with penicillin against mycoplasma and legionella pneumonia)
3. H.Pylori infection (along with PPI and either metronidazole or amoxicillin)

Question 7

What are the contraindications of using macrolides?

Answer 7

Previous macrolide hypersensivity reaction

Question 8

When should macrolide be used with caution?

Answer 8

Those with severe hepatic impairment and renal impairment as it is primary eliminated by the liver and small bit by the kidneys
Those with a QT elongation

Question 9

What are the common interactions with macrolide?

Answer 9

1. They are CYP450 inhibitors therfore inhibit the metabolism of drugs metabolised by the CYP450 system e.g. warfarin (increase bleeding) and statins (increase myopathy)
2. Drugs that prolong the QT interval/ increase susepcitbility to arrhythmia’s
   - Amiodarone, anti-psychotics, quinine, quinolone abxs, SSRIS

Question 10

What are the common side effects of macrolides?

Answer 10

It is an irritant so when given:

• Orally: nausea, vom, abdominal pain and diarrhoea
• IV: Thrombophlebitis

Also:

• Allergy
• Abx associated collitis
• Liver abnormalities e.g. cholestatic jaundice
• Prologation of QT interval (predisposing to arrhythmias)
• Ototoxicity at high doses