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PR3151 Antibiotics + Antifungals > Fluoroquinolones, Anti-folates, Nitrofurantoin, Metronidazole > Flashcards

Fluoroquinolones, Anti-folates, Nitrofurantoin, Metronidazole Flashcards

1
Q

Are fluoroquinolones bactericidal or bacteriostatic?

A

Bactericidal

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2
Q

Fluoroquinolones inhibits _________

A

DNA replication

*Bind to DNA gyrase on gram -ve, topoisomerase IV on gram +ve

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3
Q

Does fluoroquinolone require dose adjustment?

A

Dose adj in renal impairment: Ciprofloxacin
Dose adj in hepatic impairment: Moxicloxacin

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4
Q

Can topoisomerase II in eukaryotic cells be inhibited by fluoroquinolones?

A

Yes at higher concentrations

*Topoisomerase II similar to DNA gyrase (introduce negative supercoiling)

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5
Q

What are the 2 antibiotics with high risk of causing CDAD?

A

Clindamycin and Fluoroquinolones

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6
Q

Name 2 drugs that distribute to the prostatic tissue and hence can be used for prostatitis

A

Fluoroquinolones

Trimethoprim (weak base, distribute to acidic prostatic and vaginal fluids)

Cotrimoxazole

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7
Q

Fluoroquinolones are generally avoided in ______ due to high incidence of resistance.

A

Ciprofloxacin is avoided in MRSA (and MSSA), due to high incidence of staphylococcal resistance

Levo and Moxi used with caution due to fast development of resistance

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8
Q

Fluoroquinolones are ineffective against _________

A

Anaerobes

*Does not cover Bacteroides (except Moxifloxacin)

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9
Q

Fluoroquinolones generally do not cover streptococcus and enterococcus, they cover more gram-negative strains and enteric coliforms including:

A

E coli
Klebsiella
Proteus
H influenzae
Pseudomonas
Salmonella, Shigella, Campylobacter

*Not too effective against ESBL producing strains

*Can cover gram-positive Bacillus

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10
Q

Levofloxacin and Moxifloxacin are known as respiratory quinolones and can be used against _____

They have better gram-positive coverage and can be used against:

A

Streptococcus pneumoniae

Added coverage against Atypicals, Mycobacterium TB (2nd line for TB)

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11
Q

What are the adverse effects associated with Fluoroquinolones?

*There are 10

A
  1. GI related
  2. Dysglycaemia risk
  3. Aortic dissections or ruptures of aortic aneurysm (take note to not use in pt with hist of blockages or aneurysm, also do not use in pt with high BP, elderly)
  4. Incr risk of CDAD (Clindamycin as well)
  5. Headache and dizziness (caution in pt with CNS disorders such as epilepsy)
  6. Phototoxicity
    - Also in: Tetracycline, Cotrimoxazole, Pyrazinamide
  7. Incr risk of tendinitis, tendon rupture
  8. Arthropathy
  9. Prolong QT interval
    - Also in: Macrolides, Azoles,
  10. Peripheral neuropathy
    - Also in: Linezolid, Isoniazid, Nitrofurantoin, Metronidazole
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12
Q

Fluoroquinolones can have DDI, cause rise in serum levels of ____ and ______

A

Warfarin and cyclosporine

Cipro also incr serum levels of theophylline

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13
Q

What do anti-folate drugs interfere with?

A

Interfere with synthesis of amino acids, purine, pyrimidine which are precursors for DNA, RNA, and protein synthesis

*Because tetrahydrofolate cofactors are required in the synthesis of AAs, purine, pyrimidine

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14
Q

Sulfonamides inhibit _____ which _____(function)_____

A

Competitively inhibits dihydropteroate synthase, which is responsible for incorporating PABA into dihydropteroic acid

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15
Q

Trimethoprim inhibit _____ which _____(function)_____

A

Inhibit dihydrofolate reductase which reduces dihydrofolic acid to tetrahydrofolic acid

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16
Q

Explain how sulfonamides cause nephrotoxicity

A

Sulfonamides are acetylated and conjugated in the liver

Acetylated metabolite precipitate at neutral or acidic pH, form crystal, cause crystalluria => damage kidneys

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17
Q

How can nephrotoxicity be prevented when taking sulfonamides?

A

Hydration and alkalinization of urine can help to reduce conc. of drug + promote its ionization such that crystal don’t ppt

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18
Q

Sulfonamides and Trimethoprim are excreted ________, require dose adjustment in _________

A

Excreted renally, require dose adjustment in renal impairment

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19
Q

Explain why G6PD deficiency causes risk of hemolytic anemia

A

G6PD enzyme is the central factor of antioxidant defense system in RBCs, maintains high levels of reduced glutathione (GSH) and NADPH, to protect RBCs from oxidative damage caused by ROS

20
Q

Explain how sulfa drugs cause kernicterus.

A

Sulfa drugs displace bilirubin from serum albumin, bilirubin can pass into fetal CNS and penetrate BBB, thereby causing brain damage

*Hence, sulfonamides should not be used in 3rd trimester, should not be used in infants <2months
(Also not used in these pt groups due to risk of G6PD deficiency)

21
Q

Explain a possible DDI of sulfa drugs

A

Sulfa drugs can displace watfarin from serum albumin, cause potentiation of anticoagulant effect

22
Q

What might cause Trimethoprim resistance?

A
  1. Altered dihydrofolate reductase enzyme with lower affinity for trimethoprim
  2. Efflux pump
23
Q

Trimethoprim causes ______ deficiency

This results in _________

A

Folic acid (Vit B9) deficiency
*Vit B9 helps body make RBCs

This results in blood disorders such as megaloblastic anemia, leukopenia, granulocytopenia

23
Q

Trimethoprim causes ______ deficiency

This results in _________

A

Folic acid (Vit B9) deficiency
*Vit B9 helps body make RBCs

This results in blood disorders such as megaloblastic anemia, leukopenia, granulocytopenia

*Not used in 1st trimester

24
Q

How is folic acid deficiency managed?

A

Folinic acid administration

  • Folinic acid is a 5-formyl derivative of tetrahydrofolic acid, readily converted to tetrahydrofolic acid
25
Q

Cotrimoxazole (1:5, Trimethoprim : Sulfamethoxazole)

What are the two main indications?

A
  1. Simple UTI, UTI prophylaxis
  2. Pneumocystic pneumonia (fungal)
    - Symptoms: fever, rash, hyperkalemia, hyponatremia, diarrhea
26
Q

Cotrimoxazole has activity against:

A

+ve: MRSA, MSSA, Strep pneumoniae

-ve: E. coli, Klebsiella, Proteus, Haemophilus
*may have some activity against the ESBL producing strains

Others:
- Pneumocystis jiroveci (fungi)
Toxoplasma gondii (parasites)

27
Q

Cotrimoxazole does not cover:

A

anaerobes, atypicals, pseudomonas

28
Q

List some of Cotrimoxazole adverse effects

A
  1. Rashes
  2. Photosensitivity
  3. GI: nausea, vomiting
  4. Glossitis, stomatitis
  5. Hemolytic anemia (in G6PD deficiency)
  6. Blood disorders (due to folic acid deficiency)
29
Q

What is the route of administration of nitrofurantoin?

A

ORAL only

30
Q

Nitrofurantoin indications include:

A

Treatment of lower UTI, prophylaxis of lower UTI

31
Q

What is nitrofurantoin MOA?

A

Gets reduced by to highly active intermediate that inhibits various enzymes + disrupts the synthesis of proteins, DNA, RNA, and metabolic processes

32
Q

What are the 2 main organisms that Nitrofurantoin is active against?

A
  1. E coli
  2. Enterococci

*It is resistant against proteus, pseudomonas, klesiella, enterobacter

33
Q

Explain the distribution and elimination of Nitrofurantoin

A

High urinary conc. as it concentrates in the bladder

Low systemic exposure as it is rapidly cleared renally (do not use in renal impairment as it can cause incr is systemic toxicity)

34
Q

Nitrofurantoin adverse effects:

A
  1. Brown discolouration of urine
  2. GI: nausea, vomitting, diarrhea
  3. Adverse effects associated with nitroreductive metabolism (pdn of injurious oxidative free radicals)
    - Hemolytic anemia in G6PD deficiency
    - Cholestatic jaundice and hepatocellular damage (prolong incubation period to onset of liver injury)
    - Pulmonary toxicity
  4. Peripheral neuropathy (rare)
35
Q

Metronidazole is an anti-protozoal agent (mixed amebicide), can be used for the treatment of amebiasis caused by ________

A

Entamoeba histolytica trophozoites

36
Q

Explain the MOA of metronidazole

A

Metronidazole is a nitroimidazole that gets reduced as the nitro group serves as an electron acceptor, forms cytotoxic free radicals
=> result in protein and DNA damage

37
Q

Metronidazole are only active against ______ bacteria because __________

A

Anerobic bacteria

Because reduction of metronidazole requires strong reducing conditions (and anaerobic organisms have more reducing potential)

38
Q

Name the only two drugs that can treat CDAD

A
  1. Vancomycin (PO)
  2. Metronidazole (PO) - only available oral
39
Q

Name the drugs that are effective against Bacteroides

A
  1. Penicillin + BLI
  2. Carbapenems
  3. Clindamycin
  4. Moxifloxacin
  5. Metronidazole (recommended)
40
Q

What antibiotics are part of the triple therapy fo H. pylori?

A
  1. Clarithromycin (Macrolide)
  2. Amoxicillin / Metronidazole
  3. Omeprazole
41
Q

How is Metronidazole eliminated?

A

Hepatic metabolism by CYP450, parent drug and metabolites excreted via urine

*require dose adj in hepatic impairment as drug can accumulate

42
Q

What are Metronidazole adverse effects?

A
  1. GI effects
  2. Metallic taste
  3. Oral moniliasis (yeast infection in mouth)
  4. Central and peripheral nervous system effects (seizures, optic and peripheral neuropathy)
    *Avoid alcohol
43
Q

Can Metronidazole be used in pregnancy?

A

Cat B, but avoid in first trimester as it can cross placenta barrier and enter fetal circulation rapidly

44
Q

Which drugs in this series can penetrate CSF?

A

Cotrimoxazole, Metronidazole

PR3151 Antibiotics + Antifungals (5 decks)

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