Antibiotics

Question 1

What is the antibiotic treatment for a community acquired pneumonia?

Answer 1

Amoxicillin

Doxycycline or clarithromycin for penicillin allergic

Question 2

What is the basic mechanism of penicillins?

Answer 2

Cell wall synthesis inhibitors

They inhibit transpeptidase so remodelling of NAM + NAG chains can’t occur

Question 3

If penicillin allergic, which other antibiotics should be avoided?

Answer 3

Cephalosporin (also beta-lactams)

Question 4

When should you not give amoxicillin?

Answer 4

Sore throat in children - if it is EBV it will cause a rash

Question 5

What are some indications for penicillins?

Answer 5

1. Gram positive bacteria e.g. staph + strep
2. Meningococci
3. Pneumococcal infections
4. Tetanus

Question 6

What drug do penicillins interact with?

Answer 6

They reduce renal excretion of methotrexate which is a folate antagonist

Question 7

What is generally used for skin infections?

Answer 7

Flucloxacillin

Erythromycin if allergic

Question 8

Name some cephalosporins

Answer 8

Ceftriaxone
Cefazolin
Cefuroxime

Question 9

How do cephalosporins work?

Answer 9

They inhibit enzymes involved in cross-linking the cell wall

Question 10

What are cephalosporins used for?

Answer 10

UTIs
More severe infection
Antibiotic-resistant infections

Question 11

What is the main risk of cephalosporins

Answer 11

C. difficile infection

Question 12

What are the C. difficile causing antibiotics

Answer 12

Cephalosporins
Ciprofloxacin
Clarithromycin

Question 13

What drug do cephalosporins interact with?

Answer 13

Warfarin - they kill the gut flora that synthesises vitamin K so the effect of warfarin is increased

Question 14

Name some macrolides

Answer 14

Erythromycin
Clarithromycin
Azithromycin

Question 15

How is azithromycin different to the other macrolides?

Answer 15

It is not a CYP450 inhibitor

Question 16

What are the main indications for macrolides

Answer 16

LRTIs - particularly mycoplasma pneumoniae
Skin infections when penicillin allergic
Eradication of H. Pylori with amoxicillin and PPI

Question 17

Describe the mechanism of macrolides

Answer 17

They bind to 50S ribosomal subunit to inhibit protein synthesis

Question 18

What are the QT interval prolonging drugs

Answer 18

Amiodarone
Lithium
SSRIs
Quinolones
Macrolides
Antipsychotics e.g. lithium
Antihistamines

Question 19

What drugs do macrolides interact with and why?

Answer 19

They are CYP450 inhibitors

Increase the concentration of warfarin, statins, antidepressants

Question 20

Name 2 quinolones

Answer 20

Ciprofloxacin

Levofloxacin

Question 21

What are the indications for quinolones

Answer 21

UTI
GI infection - salmonella, shigella, campylobacter
HAP - pseudomonas aeroginosa

Question 22

What is the other antibiotic used to treat pseudomonas aeroginosa?

Answer 22

IV gentamicin

Question 23

What are some important side effects of quinolones?

Answer 23

• C. difficile
• Prolonged QT interval
• Rupture of achilles tendon
• Seizures

Question 24

What condition can also cause rupture of achilles tendon?

Answer 24

Cushing’s (weak tendons)

Question 25

How do quinolones interact with other drugs?

Answer 25

They are CYP450 inhibitors

Question 26

Name the CYP450 inhibitors

Answer 26

Some Certain Silly Compounds Annoyingly Inhibit Enzymes, Grr ``` Sodium valproate Ciprofloxacin Sulphonamide Cimetidine/omeprazole Antifungals, amiodarone Isoniazid Erythromycin/clarithromycin Grapefruit juice ```

Question 27

What antibiotic is used for serious gram negative aerobe infections?

Answer 27

Gentamicin

Question 28

Name some indications for gentamicin

Answer 28

Endocarditis Pyelonephritis/complicated UTI Sepsis Pseudomonas aeroginosa LRTI

Question 29

What drug class is gentamicin in? How do they work?

Answer 29

Aminoglycosides Enter cells via oxygen transport system Bind to 30S subunit of ribosomes and inhibit protein synthesis

Question 30

What antibiotics is gentamicin often used with and why?

Answer 30

Beta-lactams | To weaken the cell wall and make it more effective

Question 31

What are the 2 main side effects of gentamicin?

Answer 31

Ototoxicity | Nephrotoxicity

Question 32

When is gentamicin contraindicated?

Answer 32

Myasthenia gravis - it impairs neuromuscular transmission

Question 33

What other drugs cause ototoxicity?

Answer 33

Loop diuretics Macrolides at high doses Gentamicin Vancomycin

Question 34

Which drugs would increase risk of nephrotoxicity if given with gentamicin?

Answer 34

Ciclosporin Chemotherapy Cephalosporins

Question 35

How is co-amoxiclav effective against anaerobes?

Answer 35

Penicillins aren't effective against anaerobes. | However, the acid component (clavulanic acid) breaks down the beta-lactamases that make bacteria anaerobic

Question 36

Name a tetracycline

Answer 36

Doxycycline

Question 37

What are tetracyclines used for?

Answer 37

1. Acne vulgaris - Propionibacterium acnes 2. LRTIs - Chlamydia pneumoniae 3. Chlamydia 4. Typhoid 5. Anthrax 6. Malaria 7. Lyme disease

Question 38

What are the main side effects of tetracyclines

Answer 38

Photosensitivity | Discolouration of teeth

Question 39

Who should you not give tetracyclines to?

Answer 39

Pregnant women and children Harms teeth, bones and liver Blue/black discolouration

Question 40

What decreases absorption of tetracyclines?

Answer 40

Divalent cations e.g. calcium, antacids, iron

Question 41

What gram bacteria is vancomycin only effective against?

Answer 41

Gram positive

Question 42

Name some indications for vancomycin

Answer 42

1. MRSA 2. Severe C. difficile infection when metronidazole could not treat it 3. Endocarditis

Question 43

What kind of reaction can occur due to vancomycin?

Answer 43

Anaphylactoid reaction -> Red man syndrome

Question 44

What other side effects can vancomycin cause?

Answer 44

- Thrombophlebitis if given IV - Ototoxicity - Nephrotoxicity - Neutropenia - Thrombocytopenia

Question 45

What drug class is vancomycin in ?

Answer 45

Glycopeptides

Question 46

Name an anaerobic antimicrobial. How do they work

Answer 46

Metronidazole They enter bacteria and are reduced, which releases a free radical that prevents DNA synthesis

Question 47

What is the main contraindication for metronidazole?

Answer 47

Alcohol - it inhibits acetyldehydrogenase

Question 48

What are the main indications for metronidazole

Answer 48

1. Bacterial vaginosis 2. C. difficile 3. Dental abscesses 4. Endocarditis 5. H. Pylori eradication with amoxicillin + PPI

Question 49

What side effects might you get with metronidazole?

Answer 49

Metallic taste Dark urine Peripheral neuropathy Seizures

Question 50

What drug does metronidazole particularly interact with?

Answer 50

Lithium

Question 51

Which antibiotic inhibits folate synthesis? What should you not give it with?

Answer 51

Trimethoprim Don't give with methotrexate (folate antagonist)

Question 52

What is trimethoprim used for?

Answer 52

1. UTIs | 2. Pneumocystis pneumonia - co-trimoxazole (trimethoprim + sulfamethoxazole)

Question 53

What is an important interaction with trimethoprim?

Answer 53

It enhances the effect of warfarin

Question 54

What are the main side effects of trimethoprim?

Answer 54

Hyperkalaemia | Impaired haematopoiesis - folate deficiency

Question 55

Who should you not give trimethoprim to?

Answer 55

- Pregnant women particularly in first trimester - Folate deficiency - Renal impairment - Neonates, elderly, HIV

Question 56

Which antibiotic is used in long term UTIs or UTI prophylaxis?

Answer 56

Nitrofurantoin

Question 57

Which organisms is nitrofurantoin particularly effective against?

Answer 57

E. Coli | Staphylococcus saprophyticus

Question 58

Who should not be given nitrofurantoin?

Answer 58

Pregnant women and neonates - risk of haemolytic anaemia in the baby People with renal impairment

Question 59

Name some side effects of nitrofurantoin?

Answer 59

- Dark brown urine - Peripheral neuropathy - Pulmonary reactions - acute and chronic