Antimetabolites, DNA Synthesis Inhibitors, TB Agents

Question 1

Sulfamethoxazole

1) Mechanism of Action
2) Use
3) Spectrum

Answer 1

1) False substrates that blocks early step in folic acid synthesis reducing thymidine, purine, and methionine production
2) UTIs, Prostatitis, Toxoplasmosis
* *Generally used in combination w/ Trimethoprim**
3) Broad Spectrum

Question 2

Trimethoprim

1) Mechanism of Action
2) Use
3) Spectrum

Answer 2

1) DiHydroFolate Reductase (DHFR) inhibitor that blocks the later step in folic acid synthesis reducing thymidine, purine, and methionine production
2) Used in combination w/Sulfamethoxazole for UTIs, Prostatitis
3) Broad Spectrum

Question 3

What drugs make up Cotrimoxazole?

Answer 3

Sulfamethoxazole + Trimethoprim

Bactericidal when used together

Question 4

Ciprofloxacin

1) Mechanism of Action
2) Use
3) Adverse Effects

Answer 4

1) Inhibit bacterial topoisomerase II and IV which blocks DNA unwinding and induces IRREVERSIBLE DNA damage/degradation
2) Hospital acquired infections, Gram- Pseudomonas, Gram+ Streptococci, STDs
* *MRSA Resistant**
3) C.Difficile and MRSA colonization

Question 5

Levofloxacin

1) Mechanism of Action
2) Use
3) Adverse Effects

Answer 5

1) Inhibit bacterial topoisomerase II and IV which blocks DNA unwinding and induces IRREVERSIBLE DNA damage/degradation
2) Hospital acquired infections, Gram- Pseudomonas, Gram+ Streptococci, STDs
* *MRSA Resistant**
3) C.Difficile and MRSA colonization

Question 6

Moxifloxacin

1) Mechanism of Action
2) Use
3) Adverse Effects

Answer 6

1) Inhibit bacterial topoisomerase II and IV which blocks DNA unwinding and induces IRREVERSIBLE DNA damage/degradation
2) Hospital acquired infections, Gram- Pseudomonas, Gram+ Streptococci, STDs
* *MRSA Resistant**
3) C.Difficile and MRSA colonization

Question 7

Metronidazole

1) Mechanism of Action
2) Use

Answer 7

1) Nitro group reduction in bacterial cells generating free radical species that damage DNA
2) C.Diff, Bowel surgery prophylaxis(w/cephalosporins) Useful against Obligate anaerobes

Question 8

Name three reasons why Mycobacteria are resistant to most antibiotics.

Answer 8

1) Unique cell wall structure made of mycolic acids and peptidoglycans
2) Slow cell division and frequent dormant growth states
3) They are intracellular pathogens that live in macrophages

Question 9

Tuberculosis is a ____________ infection.

Answer 9

mycobacterial

Question 10

Is TB treated with single agent regimens or multidrug regimens?

Answer 10

Multidrug regimens

Question 11

What are the first line agents for TB?

Answer 11

Isoniazid, Rifampin, Pyrazinamide, Ethambutol

Question 12

Isoniazid

1) Mechanism of Action
2) Use

Answer 12

1) Inhibits synthesis of mycolic acids (essential component of mycobacterial cell wall)
2) Tuberculosis (TB)
* *Most active anti-TB agent!**

Question 13

Rifampin

1) Mechanism of Action
2) Use

Answer 13

1) Inhibits bacterial RNA polymerase
2) Tuberculosis
* *Strong inducer of CYP450 isozymes-leads to decreased drug levels like contraceptives & warfarin**

Question 14

Pyrazinamide

1) Mechanism of Action
2) Use

Answer 14

1) Unknown-possibly inhibit mycobacterial fatty acid synthetase
2) Tuberculosis
* *Activity enhanced at low pHs**

Question 15

Ethambutol

1) Mechanism of Action
2) Use

Answer 15

1) Inhibits synthesis of arabinoglycan component of mycobacterial cell wall
2) Tuberculosis
* *Common serious toxicity=retrobulbar (optic nerve) neuritis**