(7) Antimicrobials: Other Abx (4.1-.4.3)

Question 1

What is the precursor molecule to folate?

Answer 1

PABA

(PABA + Pteridine → → → Folate. The initial reaction only occurs in bacteria)

Question 2

MOA: Sulfamethoxazole

Answer 2

PABA analog ⇒ Inhibits dihydropteroate synthase

Question 3

MOA: Trimethoprim

Answer 3

Inhibits dihydrofolate reductase

(TmP ∝ TP)

Question 4

What type of infections is TMP-SMX first line for?

Answer 4

(1) UTI
(2) Prostatitis
(3) Nocardia
(4) Pneumocystis jirovecii
* (Prophylaxis for Toxoplasma, NOT treatment)*

Question 5

Name an antibiotic commonly used for UTIs which is also effective against MRSA

Answer 5

TMP-SMX

Question 6

Treatment: Nocardia

Answer 6

TMP-SMX

Question 7

CD4: TMP-SMX prophylaxis against Pneumocystis jirovecii

Answer 7

CD4 < 200

Question 8

CD4 Count: TMP-SMX prophylaxis against Toxoplasma gondii

Answer 8

CD4 < 100

Question 9

Treatment: Toxoplasma gondii

Answer 9

(1) Pyrimethamine
(2) + Sulfadiazine
* (TMP-SMX is preferred for PROPHYLAXIS, whereas Pyrimethamine-Sulfadiazine is preferred against an active infection)*

Question 10

Adverse Effects - Renal (2) : TMP-SMX

Answer 10

(1) Type IV renal tubular acidosis
(2) Interstitial nephritis

Question 11

Adverse Effects - In neonates (2) : TMP-SMX

Answer 11

(1) Neural tube defects
(2) Kernicterus
* (Note: TMP-SMX ⇒ Neural tube defects due to ↓ folate levels)*

Question 12

Name 3 different mechanisms by which TMP-SMX can lead to anemia

Answer 12

(1) Pancytopenia ⇒ ↓ RBCs
(2) ↓ Folate ⇒ Megaloblastic anemia
(3) ↓ GSH ⇒ Hemolytic anemia

Question 13

Name 3 adverse effects of TMP-SMX that present with cutaneous symptoms

Answer 13

(1) Atopic reaction
(2) Steven-Johnson syndrome
(3) Photosensitivity

Question 14

Name 2 reasons why TMP-SMX can lead to excessive bleeding when used with Warfarin

Answer 14

There is an increase in free Warfarin concentrate due to:

(1) Inhibition of CYP450 system
(2) Displacement from albumin

Question 15

MOA: Fluoroquinolones

Answer 15

Inhibits bacterial topoisomerase

Question 16

What type of gram (-) infections can Fluoroquinolones treat?

Answer 16

(1) Complicated UTIs
(2) Pyelonephritis
(3) Prostatitis
(4) Gastroenteritis

Question 17

Name 2 Fluoroquinolones which can be used to treat a UTI caused by Pseudomonas

Answer 17

(1) Levofloxacin
(2) Ciprofloxacin

Question 18

What type of antibiotic should you use to treat osteomyelitis in a sickle cell patient?

Answer 18

Fluoroquinolone

Question 19

Name 2 gram (+) organisms which can be treated with Fluoroquinolones

Answer 19

(1) Bacillus anthracis
(2) Strep. pneumoniae
* (Levofloxacin and Moxifloxacin are the respiratory fluoroquinolones)*

Question 20

Name 2 classes of antibiotics which exhibit reduced potency when taken with divalent cations

Answer 20

(1) Fluoroquinolones
(2) Tetracyclines

Question 21

Adverse Effects (4) : Flouroquinolones

Answer 21

(1) Torsades
(2) GI distress
(3) Tendon rupture
(4) Teratogen
* (Teratogen ⇒ Abnormal cartilage development)*

Question 22

Name 2 classes of antibiotics associated with Torsades de pointes

Answer 22

(1) Flouroquinolones
(2) Macrolides

Question 23

Name 2 factors which increase the risk of Fluoroquinolone-induced tendon rupture

Answer 23

(1) Old age
(2) Glucocorticoids

Question 24

In what age group are Fluoroquinolones contraindicated?

Answer 24

<10 y/o

Question 25

Name 2 poorly gram staining organisms which can be treated with Fluoroquinolones

Answer 25

(1) Mycoplasma
(2) Legionella
* (Legionella is technically gram (-), but stains poorly so I included it here)*

Question 26

What antibiotic is particularly effective against polymicrobial anaerobic infections?

Answer 26

Metronidazole

(i.e., intra-abdominal infections)

Question 27

MOA: Metronidazole

Answer 27

Free radical metabolites ⇒ DNA damage

(∴ Bacteriocidal)

Question 28

Name 3 protozoal infections Metronidazole is used to treat

Answer 28

(1) Entamoeba histolytica
(2) Giardia lamblia
(3) Trichomonas vaginalis

Question 29

Name 3 bacterial infections Metronidazole is used to treat

Answer 29

(1) Gardnerella vaginalis
(2) Helicobacter pylori
(3) Clostridium
* (And other anaerobes)*

Question 30

What antibiotic can substitute for Amoxicillin in the treatment of H. pylori?

Answer 30

Metronidazole

Question 31

As a general rule, compare when you would use Metronidazole vs. Clindamycin

Answer 31

In the treatment of ANAEROBIC bacteria,

(1) Metronidazole: Below the diaphragm
(2) Clindamycin: Above the diaphragm

Question 32

What is the drug of choice for pseudomembranous colitis caused by Clostridium difficile?

Answer 32

Metronidazole

Question 33

Adverse Effect: Metronidazole

Answer 33

Disulfiram-like reaction

Question 34

Name an (1) antibiotic and (2) endocrine drug which have been associated with a Disulfiram-like reaction

Answer 34

(1) Antibiotic: Metronidazole
(2) Endocrine: Chlorpropamide

Question 35

What are the class IV antiarrhythmics?

Answer 35

(1) Verapamil
(2) Diltiazem

Question 36

MOA: Class IV antiarrhythmics

Answer 36

Calcium channel blockers

(Non-dihydropyridine reduce Δ of AP upstroke in SA/AV)

Question 37

What type of arrhythmias can class IV antiarrhythmics treat?

Answer 37

Supraventricular

Question 38

Where do class IV antiarrhythmics exert the strongest effect?

Answer 38

AV node

Question 39

What effect do class IV antiarrhythmics have on EKG tracing?

Answer 39

Prolonged PR interval

(And ∴ can cause heart block)