Tetracyclines Flashcards
Example of Tetracycline’s
Doxycycline, Lymecycline
How do Tetracycline’s work?
Tetracyclines inhibit bacterial protein synthesis. They bind to the ribosomal 30S subunit found specifically in bacteria. This prevents binding of transfer RNA to messenger RNA, which prevents addition of new amino acids to growing polypeptide chains. 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.
Tetracyclines were discovered in 1945 and have been widely used. Consequently, some bacteria have acquired resistance to these antibiotics. A common mechanism is through acquisition of an efflux pump, which allows bacteria to pump out tetracyclines, preventing cytoplasmic accumulation.
Indications for Tetracycline’s
Acne vulgaris, particularly where there are inflamed papules, pustules and/or cysts (Proprionibacterium acnes).
Lower respiratory tract infections including infective exacerbations of COPD (e.g. Haemophilus influenzae), pneumonia and atypical pneumonia (mycoplasma, Chlamydia psittaci, Coxiella burnetii [Q fever]).
Chlamydial infection including pelvic inflammatory disease.
Other infections such as typhoid, anthrax, malaria and Lyme disease (Borrelia burgdorferi).
ConrtraIndications for Tetracycline’s
Tetracyclines bind to teeth and bones during fetal development, infancy and early childhood and so should not be prescribed during pregnancy, breastfeeding or for children ≤12 years of age.
They should be avoided in people with renal impairment as their anti-anabolic effects can raise plasma urea and reduced excretion can increase the risk of adverse effects.
Side effects of Tetracycline’s
As antibiotic structures are different, there is no cross-reactivity with penicillins or other β-lactam antibiotics.
Tetracycline-specific side effects include: oesophageal irritation, ulceration and dysphagia; photosensitivity (an exaggerated sunburn reaction when skin is exposed to light); and discolouration and/or hypoplasia of tooth enamel if prescribed for children. Intracranial hypertension is a rare adverse effect causing headache and visual disturbance.
Common Antibiotic : nausea, vomiting and diarrhoea, although they are considered to be among the lowest risk antibiotics for Clostridium difficile infection
Rare: Hypersensitivity reactions occur in ~1%
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Interactions of Tetracycline’s
Tetracyclines bind to divalent cations. They should therefore not be given within 2 hours of calcium, antacids or iron, which will prevent antibiotic absorption.
Tetracyclines can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesise vitamin K.
Elimination of Tetracycline’s
Renal
Patient information on Tetracycline’s
The duration of treatment depends on the indication; for example, 5–7 days in infective exacerbations of COPD, 8 weeks in acne.
The duration of treatment depends on the indication; for example, 5–7 days in infective exacerbations of COPD, 8 weeks in acne.
Explain that the aim of treatment is to get rid of infection and improve symptoms. For oral treatment, encourage the patient to complete the prescribed course. Before prescribing, always check with your patient personally or get collateral history to ensure they have no allergy to tetracyclines. Warn them to seek medical advice if a rash or other unexpected symptoms develop. If an allergy develops during treatment, give the patient written and verbal advice not to take this antibiotic in the future and make sure that the allergy is clearly documented in their medical records.
Clinical tip—Tetracyclines can cause nausea and vomiting when taken on an empty stomach, which can be reduced by taking these antibiotics with food. However, tetracyclines should not be taken with dairy products as calcium in the gastrointestinal tract binds tetracyclines and prevents their absorption.
