Antibiotics: Tetracyclines

Question 1

Indications of tetracyclines?

Answer 1

Acne vulgaris (inflamed papules, pustules, cysts)

LRTI including:
- infective exacerbation of COPD, pneumonia, atypical pneumonia.

PID, Chlamydial infection

Other infections:
- Typhoid​
- Anthrax​
- Malaria​
- Lyme disease

Question 2

Spectrum of activity?

Answer 2

Broad spectrum

Works against Gram-positive and Gram-negative organisms.

Question 3

MOA of tetracyclines?

Answer 3

Inhibits bacterial protein synthesis -BACTERIOSTATIC

Binds to 30S subunit of the bacterial ribosome and prevents tRNA from binding to mRNA.
→ this prevents addition of new amino acids to help grow polypeptide chains.

Question 4

Adverse effects of tetracyclines?

Answer 4

Nausea
Vomiting
Diarrhoea

Hypersensitivity reactions

Oesophageal irritation
Ulceration
Dysphagia

Photosensitivity
Discolouration and/or hypoplasia of tooth enamel in children

Hepatoxicity

Intracranial hypertension
- headache
- visual disturbance

Question 5

Warnings of tetracyclines?

Answer 5

Can bind to teeth and bones during fetal development, infancy, and early childhood.

Avoid in:
- pregnancy
- breastfeeding
- children ≤12years

Caution in renal impairment due to antianabolic effects can raise serum urea.
→ reduced excretion of this can increase the risk of adverse effects.

Question 6

Interactions of tetracyclines?

Answer 6

Binds to divalent cations.
→ so should not be given within 2 hours of calcium, antacids or iron.
→ the above prevents abx absorption.

Enhances anticoagulant effect of warfarin by killing normal gut bacteria that synthesis vitamin K.

Question 7

Monitoring of tetracyclines?

Answer 7

Check infection resolves by:
- symptoms/signs improved (e.g. reduction in inflamed papules, pustules, and cysts in acne)
- blood markers e.g. falling CRP

Question 8

Pt education of tetracyclines?

Answer 8

Aims to get rid of infection and improve symptoms.

Check for tetracycline allergy.

Seek medical advice if they develop a rash or unexpected symptoms.

If allergy develops during treatment, give pt written and verbal advice NOT to take this abx class in future and make sure that the type of reaction (including its nature) is clearly documented in pt’s medical records.

Advise pt to take tx during a meal with a full glass water when sitting or standing.

Avoid indigestion remedies.

Avoid medicine containing iron or zinc 2 hours before and after taking the abx

During tx, they should protect their skin from sunlight.

Question 9

Examples of tetracycline?

Answer 9

doxycycline
lymecycline