Tetracyclines

Question 1

MOA of tetracyclines

Answer 1

• Prevents protein synthesis by binding to 30S subunit of ribosomes (bacteriostatic)
• Broad spec

Question 2

What is the indication of tetracyclines?

Answer 2

• Chlamydia
• Malaria prophylaxis
• RTI
• Acne
• Rosacea

Question 3

Give examples of tetracyclines

Answer 3

• Doxycycline (dose: 200mg OD, malaria prophylaxis + chlamydia)
• Minocycline (broader spec - rare use due to harsh s/e)

Question 4

What are the side effects of tetracyclines?

Answer 4

Benign intracranial hypertension
- Symptoms: headache + visual disturbances

Tooth discolouration + dental hypoplasia

• CI: children under 12 + pregnant/breastfeeding
• Limecycline: CI <8
• Doxycycline: given w caution in children aged 8-11 for severe acute infections OR 8: severe life threatening infections

Question 5

Tetracylines + renal impairment

Answer 5

Avoid (except doxycycline + minocycline)

Question 6

Tetracyclines + hepatic impairment

Answer 6

Avoid

Question 7

What are the interactions of tetracyclines?

Answer 7

Hepatotoxicity w hepatotoxic drugs
- Co-amox
- Flucox
- Isoniazid
- Carbamazepine + valproate
- Fluconazole
- Methotrexate
- Statins

Question 8

What are the counselling point for tetracyclines?

Answer 8

Photosensitivity
- Demeclocycline + doxycycline: avoid sunlight or sun lamps
- Label: protect your skin from sunlight, even on bright but cloudy day. Do not use sun bed

Avoid antacids, iron or zinc: 2H gap

DOT: democlocycline, oxytetracycline, tetracycline → Avoid milk + empty stomach
- Label: Take this medicine when your stomach is empty. This means an hour before food or 2 hours after food

DMT: doxycycline, minocycline, tetracycline → oesophagitis (ulcers, dysphagia)
- Swallow whole w plenty of fluid sitting or standing