2. Macrolides

Question 1

Examples of macrolides

Answer 1

Erythromycin, Clarithromycin, Azithromycin

Question 2

Macrolide spectrum of activity

Answer 2

Have a similar spectrum of activity to penicillins. They are broad spectrum antibiotics.
Are active against many penicillin resistant stapphylococci

Question 3

Macrolide mechanism of action

Answer 3

Prevents bacterial protein synthesis by binding to the 50S subunit of ribosomes - bacteriostatic.

Question 4

Macrolide indications

Answer 4

Commonly treat respiratory tract infections like chlamydia, pneumonia and H.pylori. Also treat skin and soft tissue infections.

Question 5

Macrolide dosages

Answer 5

Azithromycin - BD (available OTC)
Clarithromycin - BD
Erythromycin QDS/BD and is the safest macrolide to take in pregnancy

Question 6

When are macrolides are typically given?

Answer 6

In penicillin-allergic patients

Question 7

Macrocolides typically treat

Answer 7

Campylobacter enteritis, Respiratory tract infections (such as pneumonia, whooping cough, legionella, chlamyida and mycoplasma infections) and skin infections

Question 8

Typical side effects of macrolides and its management

Answer 8

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

Question 9

Describe azithromycin half life

Answer 9

long half life therefore once daily dosage is recommended

Question 10

What is azithromycin typically used to treat

Answer 10

Uncomplicated genital chlamydia, uncomplicated gonorrhoea, typhoid, trachoma, Lyme disease, H. pylori

Question 11

Macrolide cautionary criteria

Answer 11

may predispose patient to QT prolongation, may aggravate myasthenia graves (particularly erytrhomycin)

Question 12

Macrolide common side effects

Answer 12

Reduced appetite, diarrhoea, dizziness, gastrointestinal discomfort (mainly with erythromycin)

Disturbances in taste is associated with clarithromycin

Question 13

Impact of exposure to Erythromycin in early infancy

Answer 13

Increased risk of infantile hypertrophic pyloric stenosis

Question 14

Interaction considerations

Answer 14

Erythromycin and Clarithromcyin are potent enzyme inhibitors

Question 15

Penicillins should never be used in this administration route

Answer 15

Intrathecal injection, due to risk of encephalopathy - can be FATAL

Question 16

Macrolides should be used with caution

Answer 16

In patients with hepatic impairment

Question 17

Appropriateness of macrolides with pregnancy

Answer 17

Macrolides should be avoided in pregnancy, though erythromycin can be given if the benefits OUTWEIGH the risks.

Question 18

Macrolides counselling/labels

Answer 18

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

Question 19

Macrolide drug interactions

Answer 19

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.