2. Macrolides Flashcards
Examples of macrolides
Erythromycin, Clarithromycin, Azithromycin
Macrolide spectrum of activity
Have a similar spectrum of activity to penicillins. They are broad spectrum antibiotics.
Are active against many penicillin resistant stapphylococci
Macrolide mechanism of action
Prevents bacterial protein synthesis by binding to the 50S subunit of ribosomes - bacteriostatic.
Macrolide indications
Commonly treat respiratory tract infections like chlamydia, pneumonia and H.pylori. Also treat skin and soft tissue infections.
Macrolide dosages
Azithromycin - BD (available OTC)
Clarithromycin - BD
Erythromycin QDS/BD and is the safest macrolide to take in pregnancy
When are macrolides are typically given?
In penicillin-allergic patients
Macrocolides typically treat
Campylobacter enteritis, Respiratory tract infections (such as pneumonia, whooping cough, legionella, chlamyida and mycoplasma infections) and skin infections
Typical side effects of macrolides and its management
Nausea, vomiting and diarrhoea though managed by providing a lower dose, commonly seen with erythromycin.
Can prolong the QT interval, predisposing the patient to dangerous arrhythmias. Increased risk of this with erythromycin. Patient must report signs of a cardiovascular event such as fainting, dizziness, shortness of breath, heart palpitations. Used in caution with drugs that cause hypokalaemia or that already prolong QT interval.
Taste disturbances, tongue discolouration are also another side effect
Describe azithromycin half life
long half life therefore once daily dosage is recommended
What is azithromycin typically used to treat
Uncomplicated genital chlamydia, uncomplicated gonorrhoea, typhoid, trachoma, Lyme disease, H. pylori
Macrolide cautionary criteria
may predispose patient to QT prolongation, may aggravate myasthenia graves (particularly erytrhomycin)
Macrolide common side effects
Reduced appetite, diarrhoea, dizziness, gastrointestinal discomfort (mainly with erythromycin)
Disturbances in taste is associated with clarithromycin
Impact of exposure to Erythromycin in early infancy
Increased risk of infantile hypertrophic pyloric stenosis
Interaction considerations
Erythromycin and Clarithromcyin are potent enzyme inhibitors
Penicillins should never be used in this administration route
Intrathecal injection, due to risk of encephalopathy - can be FATAL
Macrolides should be used with caution
In patients with hepatic impairment
Appropriateness of macrolides with pregnancy
Macrolides should be avoided in pregnancy, though erythromycin can be given if the benefits OUTWEIGH the risks.
Macrolides counselling/labels
As absorption of some macrolides are affected by food or indigestion remedies
BEFORE FOOD:
Azithromycin capsules should be taken when the stomach is empty. Meaning an hour before food or 2 hours after food.
AFTER FOOD
Clarithromcyin should be taken with or just after a meal
INDIGESTION REMEDIES
Azirthromcyin and Erythromycin: Should not be taken with indigestion remedies 2 hours before or after taking this medicine
Macrolide drug interactions
Erythromycin and Clarithromycin are cytochrome P450 enzyme inhibitors. Causes many interactions and increases levels of drugs in the body.
Macrolides interact with statins, as there is an increased risk of myopathy. Patients must temporarily stop statins until they have completed their antibiotic course.
Macrolides increase the anticoagulant effect of warfarin. Especially erythromycin with rivaroxaban.
Macrolides already prolong the QT interval. If taken with drugs that further prolong the QT interval, increases the risk of ventricular arrhythmias.
Drugs that prolong QT interval (antipsychotics, ani-arrhythmics, SSRI’s like, escitalopram and citalopram clarithromcyin, erthyromcyin, lithium, methadone, 5HT3 antagonists, clomipramine, domperidone, hydroxyzine). Hypokalaemia is a risk factor for prolonged QT interval
When you combine drugs that cause hypokalaemia at the same time as a drug that prolongs the QT interval, it increases the risk of a life-threatening ventricular arrhythmia called torsades de pointes. Example of this includes beta agonists + loop/thiazide diuretics.
