Tetracyclines

Question 1

Name some common tetracyclines?

Answer 1

Doxycycline

Lymecylcine

Question 2

What part of the bacterial cell do tetracyclines target?

Answer 2

Protein synthesis

Question 3

How do tetracyclines work?

Answer 3

Bind to the 30S subunit if bacterial ribosomes
This binding inhibits the binding of transfer RNA to messenger RNA so amino acids cannot be added to the growing polypeptide chain.
This inhibition of bacterial protein synthesis has a bacteriostatic effect allowing the bodies immune system to fight and kill the bacteria

Question 4

Are tetracyclines bactericidal or bacteriostatic?

Answer 4

Bacteriostatic

Question 5

What spectrums do tetracyclines have?

Answer 5

Brodspectrum relatively

Question 6

Is there resistance against tetracyclines and how?

Answer 6

Yes

Efflux pump allowing bacteria to pump out tetracyclines

Question 7

What are the common uses for tetracyclines?

Answer 7

1. Acne Vulgaris: against proprion bacterium acnes
2. Lower Respiratory Tract infections
   - Acute exacerbations in COPD (H.Influenza)
   - Pneumonia and Atypical Pneumonia (mycoplasma, chlymydia psittaci and Coxiella burnetti - Q fever)
3. Chlamydial Infections (including pelvic inflammation disease)
4. Other infections e.g. Lyme disease, Typhoid, malaria and Anthrax

Question 8

What atypical bacteria species in pneumonia do tetracyclines work against?

Answer 8

Mycolplasma, chlamydial psittaci, Coxiella burnetti - Q fever

Question 9

What are the contra-indications of tetracyclines?

Answer 9

1. Pregnant women
2. Breastfeeding women
3. Children <12

Question 10

When should tetracyclines be used with caution?

Answer 10

1. Renal Impairment
2. Myasthenia gravis
   - due to anti-anabolic effects causing muscle weakness and reduced excretion

Question 11

What are the common side effects with tetracyclines?

Answer 11

• GI upset (although lowest risk of c.diff)
• Hypersentitvity
• Oesophageal irritation/ulceration
• Dysphagia
• Photosensitivity
• Teeth staining/hypopigmentation
• Intercranial hypertension (causes headache and visual disturbances)

Question 12

What are some common interactions with tetracyclines?

Answer 12

• Iron, calcium and antacids (tetracyclines bind to these and therefore there is reduced abx absorption)
• warfarin

Question 13

What advice should you give to patients about when to take their tetracylines?

Answer 13

Dont take on empty stomach - nausea and vom

dont take with milk or calcium - binds to tetracycline reducing absorption