Lyme disease

Question 1

Tetracyclines

Common indications

Answer 1

1. Acne vulgaris- particularly where there sre inflammed papules, pustules or cysts
2. Lower respiratory treat infections including infective exacerbations of COPD (H.influenza), Pneumonia and atypical pneumonia
3. Chlamydial infection including PID (pelvic inflammatory disease)
4. Other infections such as typhoid, anthrax, malaria and lyme disease

Question 2

Tetracyclines

MOA

Answer 2

• Tetracyclines inhibit bacterial protein synthesis
• They bind to the ribosomal 30S subunit found specifically in bacteria
• This prevents binding of tRNA to mRNA, which prevents the addition of new amino acids to growing polypeptide chains
• Inhibition of protein synthesis is bacteriostatic (stop bac growth), which assists the immune system in killing and removing bacteria from the bldy
• Tetracyclines have a relatively broad spectrum of anti-bac activity
• Tetracyclines were discovered in 1945 and have been widely used
• Consequently, some bacteria have aquired resistance to these antibiotics
• A common mechanism is through acquisition of efflux pump, which allows bacteria to pump out tetracyclines, preventing cytoplasmic accumulation

Question 3

Tetracyclines

Adverse effects

Answer 3

• Most antibiotics, tetracycline cause N&V and diarrhoea, although they are considered to be among the lower risk antibiotics for C.diff infection
• Hypersentivity reactions occur in 1% of people- NO cross-sensitivity with penicillins
• Tetracycline-specific side effects include: oesophageal irritation, ulceration and dysphagia, photosensitvity, discolouration and hypoplasia of thooth enamel if prescribed for children
• Intracranial HTN is a rare adverse effect cause headache and visual disturbances

Question 4

Tetracyclines

Warnings

Answer 4

• Tetracyclines bind to teeth and bones in fetal development so are contraindicated in pregnancy and breastfeeding and for children <12yrs old
• Renal impairment as their anti-anabolic effects can raise plasma urea and reduced excretion can increase the risk of advese effects

Question 5

Tetracyclines

Interactions

Answer 5

• Tetracyclines bind to divalent cations
• They should therefore not be given within 2 hrs of calcium, antacids or Fe which will prevent absorption
• Tetracyclines can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesis vitamin K

Question 6

Tetracyclines

Prescription

Answer 6

• Duration depends on the indication
• Most are 5-7 days e.g. infective exacerbation of COPD, 8 weeks in acne

Question 7

Tetracyclines

Administration

Answer 7

• Are usually formulated as capsules or tabs
• These should be swallowed whole with plenty of water while sitting or standing to stop them getting stuck in the oesophagus where they may cause ulceration