Tetracylines Flashcards
What are examples of tetracyclines?
Doxycycline
Lymecycline
What are examples of glycylcline?
Tigecycline
What are five common indications?
Acne vulgaris
Lower RTI (infective COPD and pneumonia )
Chlamydia
Typhoid, malaria and Lymes
Tigecycline- severe skin, soft tissue and abdominal infection
What is their spectrum of activity?
Broad spectrum
Gram positive and negative
What is the mechanism of tetracycline
Inhibits bacterial protein synthesis
Binds to 30s subunit which binds to bacteria.
This stops translocation
Bacteriostatic
What is the mechanism of resistance of bacteria
Resistance is widespread in gram positive
-effluent pump
Allows bacteria to pump out tetracyclines
What is the advantage of Tigecycline over tetracyclines ?
Tigeyclycline- glycylcycline antibiotic which is structurally and mechanistically similar to tetracyclines, but less susceptible to resistance.
What are important side effects?
Gi upset
C.diff
Tetracycline specifically- oesophageal ulceration
Dysphagia
Photosensitivity
Discolouration and/or hypoplasia of tooth enamel
What are uncommon side effects?
Hepatotoxicity
Intracranial hypertension - causes headache and visual disturbance
What are warnings and cautions of tetracyclines?
Caution in renal impairment as their antianabolic effects can rise serum urea and reduced drug excretion
This increases risk of Side effects
What groups of people should not be prescribed tetracyclines?
NOT PRESCRIBED IN:
Pregnancy
Breastfeeding
Children younger than 12
(Can bind to teeth and bones during childhood development)
What electrolytes should be not be taken with tetracyclines and why?
Calcium, antacids and iron
Has to be taken at least 2 hours apart
Concurrent use can prevent antibiotic absorption as tetracyclines bind to divalent cations
What are other interactions with tetracyclines?
Warfarin
They enhance the anticoagulant effect by killing normal gut bacteria that synthesise vitamin K
What are dosages?
Doxycycline:
200mg day one and 100mg for 6 days
Lymcycline:
Acne 8 weeks
COPD infective exacerbation:
5-7 days
Higher doses needed in more severe infections
Tigecycline only given orally
What are patient counselling points?
Swallowed whole
Plenty of water
Sitting up or standing for 30min after admin
This avoids it getting stuck in oesophagus where it can cause ulceration
Avoid sunlight even on cloudy days
