Tetracyclines Flashcards
What is the general action of tetracyclines?
Bacteriostatic
Binds to 30S ribosomes (and 50S to a lesser extent)
Inhibits bacterial protein synthesis
Name some common tetracyclines?
Tetracycline
Lymecycline
Doxycycline
What is the pharmacokinetic of doxycycline?
Oral bioavailability = 73-95%
Protein binding = plasma proteins (limited info available)
Half-life = limited info available
Metabolism = limited info available
Excretion = concentrated in bile by the liver, excreted in urine and faeces
Which bacteria is doxycycline effective against?
Gram +ve cocci = Streptococci
Gram -ve bacilli = E. coli
Gram -ve cocci = N. meningitis
Atypicals
What are the indications for doxycycline?
Susceptible infection e.g., chlamydia, rickettsia and mycoplasma
Severe infections (including refractory UTIs)
Acute sinusitis
Acute cough (if systemically very unwell or at higher risk of complications)
CAP
HAP
Acute exacerbation of bronchiectasis
Acute exacerbation of COPD
Mild diabetic foot infection
Cellulitis, erysipelas
Leg ulcer infection
Prophylaxis/treatment of infection from human or animal bites
Acne vulgaris
Rosacea
Papulopustular facial rosacea
Early syphilis
Late latent syphilis
Neurosyphilis
Uncomplicated genital chlamydia, non gonococcal urethritis
PID
Lyme disease
Anthrax
Malaria prophylaxis
Adjunct to quinine in Tx of Plasmodium falciparum malaria
Periodontitis
Tx of recurrent aphthous ulceration
Rocky mountain spotted fever
What is the typical dosing of doxycycline?
200mg daily for 1 dose
Then maintenance 100mg PO OD (length of days vary according to indication)
OR
just 100mg PO, OD/BD
What are the common side effects of tetracyclines in general?
Diarrhoea
N+V
Angioedema
Headache
HSP
Pericarditis
Hypersensitivity
SLE exacerbation
Skin reactions
Photosensitivity reaction
What are the uncommon side effects of tetracyclines in general?
Dizziness
Pancreatitis
What are the rare side effects of tetracyclines in general?
Decreased appetite
Thyroid gland discolouration
Dysphagia
Eosinophilia
Bulging fontanelle (in infants)
GI disorders
Glossitis
Haemolytic anaemia
Hepatic disorders
Idiopathic intercranial HTN
Increased infection risk
Neutropenia
Pseudomembranous enterocolitis
SJS
Thrombocytopenia
What is the frequency side effects of tetracyclines in general?
Tooth discolouration
If a patient on a tetracycline develops a headache or visual disturbance what should you do?
Headache and visual disturbances may indicated a benign intercranial hypertension
Stop treatment if raised intercranial pressure develops
What are the common side effects of doxycycline?
Dyspnoea
Hypotension
Peripheral oedema
Tachycardia
What are the uncommon side effects of doxycycline?
GI discomfort
What are the rare/very rare side effects of doxycycline?
Abx associated colitis
Anxiety
Arthralgia
Flushing
Raised ICP with papilloedema
Jarisch-Herxheimer reaction
Myalgia
Severe cutaneous adverse reactions (SCARs)
Skin hyperpigmentation (with long term use)
Stomatitis
Tinnitus
Vision disorders
Can tetracyclines be given to pregnant or breastfeeding women?
NO
What advise should you give people on how to take doxycycline capsules/tablets?
Drink with plenty of water
Whilst sitting or standing
Avoid lying down for at least 30 mins after taking doxycycline
Space the doses evenly throughout the day
Keep taking the medication until the course is finished, unless you are told to stop
It should not be taken together with dairy products, or calcium rich products as it can stop the body from absorbing the drug
What should patients not take with doxycycline?
Ingestion tablets
Medicines containing iron or zinc
2 hours before or after they take doxycycline
TRUE OR FALSE
Patients on doxycycline should protect their skin from sunlight
TRUE
Even on a bright but cloudy day
What are the significant drug interactions for doxycycline?
doxy + warfarin/acenocoumarol = increases anticoagulant effect - monitor INR
doxy + acitretin/alitretinoin/isotretinoin/tretinoin = increased risk of benign intercranial hypertension
doxy + ciclosporin = increased [ciclosporin]
doxy + lithium = increased risk of lithium toxicity
doxy + phenindione = increases anticoagulant effect of phenindione - monitor INR
Which group of people should you apply caution too when prescribing tetracyclines?
Myasthenia gravis - muscle weakness may be increased
SLE - can be exacerbated
Which group of people may doxycycline not be suitable for?
allergic reaction to doxycycline or any other medicine
kidney or liver problems
oesophagitis
SLE
myasthenia gravis
pregnant or breastfeeding
What are the common indications of lymecycline?
Acne (mainly)
Chest infections
Sinusitis
STIs
Infections in, or around, the mouth
What is the typical dosage of lymecycline for acne Tx?
1 capsule 408 mg OD
What advise should you give people on how to take lymecycline capsules?
Drink with plenty of water
Whilst sitting or standing (important the capsule is not stuck in throat as it could cause irritation)
Do not take the capsule just before bed
It can be taken with or without food - but less likely to feel sick if taken with food
