Chlamydia

Question 1

Tetracycline (Doxycycline)

Common indications

Answer 1

1. Acne vulgaris- particularly where there are inflamed papules, pustules and or cysts
2. Lower respiratory tract infection- Including infective exacerbations of COPD, Pneumonia and atypical pneumonia
3. Chalmydia- including PID
4. Other infections of the thyroid, anthrax, malaria and lyme disease

Question 2

Tetracycline (Doxycycline)

MOA

Answer 2

• Tetracycline inhibits bacterial protein synthesis
• They bind to the ribosomal 30S subunit found specifically in bacteria, this prevents binding of transfer RNA to mRNA, which prevents the addition of new amino acids to the growing polypeptide chain
• Inhibition of protein synthesis is bacteriostatic (stops bacterial growth), which assists the immune system in killing and removing bacteria from the body
• Tetracyclines have a relatively broad spectrum of antibacterial activity, resistance including efflux pump and reduced bacterial accumulation

Question 3

Tetracycline (Doxycycline)

Adverse effects

Answer 3

• N&V, diarrhoea
• risk of c.dif
• Hypersensitivity- there is no cross-reactivity with other penicillins
• Oesophageal irritation, ulceration and dysphagia
• Photosensitivity
• discolouration of tooth enamel
• Intracranial HTN cause headache and visual disturbances

Question 4

Tetracycline (Doxycycline)

Warnings

Answer 4

• Should NOT be used in pregnancy, breastfeeding and U12
• Avoid in renal impairment

Question 5

Tetracycline (Doxycycline)

Interactions

Answer 5

• Bind to divalent cations, They should therefore not be given within 2 hours of calcium, antacids or Fe will prevent antibiotic absorption
• Tetracyclines can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesises vit K

Question 6

Other options

Answer 6

• Azoithromycin
• Amoxicillin
• Erythromycin