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PHARM MIDTERM2 > DRUGS AFFECTING NUCLEIC ACID SYNTHESIS > Flashcards

DRUGS AFFECTING NUCLEIC ACID SYNTHESIS Flashcards

1
Q

DRUGS AFFECTING NUCLEIC ACID SYNTHESIS

A

1) FLUOROQUINOLONES
2) SULFONAMIDES
3) TRIMETHOPRIM

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2
Q

FLUOROQUINOLONES

GENERATIONS

A

1st Gen = NALIDIXIC ACID (QUINOLONE)

2nd Gen = CIPROFLOXACIN –> is SYNERGISTIC with B-lactams

3rd Gen = LEVOFLOXACIN –> excellent activity against S. pneumoniae

4th Gen = GEMIFLOXACIN, MOXIFLOXACIN

LOWER GEN = HIGHER GRAM -VE ACTIVITY

HIGHER GEN = HIGHER GRAM +VE ACTIVITY

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3
Q

DOC FOR UNCOMPLICATED UTI:

A

1st gen FLUOROQUINOLONES = NALIDIXIC ACID

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4
Q

DOC FOR TRAVELERS DIARRHEA (E. COLI)

A

2ND GEN FLUOROQUINOLONE: CIPROFLOXACIN

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5
Q

DOC FOR PSEUDOMONAS AERUGINOSA (CF PATIENTS) EVEN CHILDREN

A

2nd gen fluoroquinolone = CIPROFLOXACIN

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6
Q

PROPHYLAXIS AGAINST MENINGITIS (alternative to ceftriaxone and rifampin)

A

2nd Generation Fluoroquinolone: CIPROFLOXACIN

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7
Q

DOC FOR PROSTATITIS (E. COLI)

A

3rd GENERATION FLUOROQUINOLONE: LEVOFLOXACIN

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8
Q

WHEN TO USE 3RD + 4TH LINE FLUOROQUINOLONES?

A

Levofloxacin, moxifloxacin & gemifloxacin (excellent activity against S.pneumoniae, H.influenzae & M.catarrhalis)

Used in treatment of pneumonia when:

  • First-line agents have failed
  • In the presence of comorbidities

• Patient is an inpatient

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9
Q

FLUOROQUINOLONES CLINICAL APPLICATIONS TABLE

A
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10
Q

FLUOROQUINOLONES PK + AE

A

PK:

  • Good oral bioavailability
  • Well distributed into all tissues and fluids (including

bones)

  • Iron, zinc, calcium (divalent cations) interfere with absorption, so DON’T TAKE WITH MILK OR ANTACIDS
  • Dosage adjustments required in renal dysfunction (except

moxifloxacin)

AE:

  • GI distress
  • CNS, rash, photosensitivity
  • Connective tissue problems (avoid in pregnancy, nursing mother, under 18’s) – Black Box Warning!
  • QT prolongation (moxifloxacin, gemifloxacin, levofloxacin)
  • High risk of causing superinfections (C.difficile, C albicans, streptococci)
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11
Q

FLUOROQUINOLONES - INTERACTIONS + CONTRAINDICATIONS

A

INTERACTIONS:

Theophylline, NSAIDs & corticosteroids = enhance toxicity of fluoroquinolones

• 3rd & 4th generation = raise serum levels of warfarin, caffeine & cyclosporine

CONTRAINDICATIONS:

  • *Pregnancy & nursing mothers**
  • *• Children < 18y** (unless benefits outweigh risks)
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12
Q

SULFAMETHOXAZOLE

SULFADIAZINE

SULFASALAZINE

A

SULFONAMIDES

  • Structural analogs of p-aminobenzoic acid (PABA)
  • Bacteriostatic against Gram-positive & Gram-negative organisms

MOA:

  • Inhibit bacterial folic acid synthesis
  • Synthetic analogs of PABA (p-amino-benzoic acid)
  • Competitive inhibitors (& substrate) of dihydropteroate synthase
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13
Q

SULFONAMIDES - RESISTANCE

A

Plasmid transfers / random mutations that:

  • Altered dihydropteroate synthase
  • Decreased cellular permeability
  • Enhanced PABA production
  • Decreased intracellular drug accumulation
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14
Q

SULFONAMIDES - CLINICAL APPLICATIONS

Infrequently used as single agents (resistance)

  • Topical agents (ocular, burn infections)
  • Oral agents (simple UTI’s)
  • Sulfasalazine (oral) = ulcerative colitis, enteritis, IBD
A
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15
Q

SULFONAMIDE PK + AE

A
  • Oral or topical
  • Can accumulate in renal failure
  • Acetylated in liver. Can precipitate at neutral or acidic pH –> kidney damage

AE:

  • GI distress, fever, rashes, photosensitivity are common
  • Crystalluria (nephrotoxicity)
  • Hypersensitivity reactions
  • Hematopoietic disturbances (esp. patients with G6PD deficiency)
  • Kernicterus (in newborns and infants <2 months)
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16
Q

SULFONAMIDES - DRUG INTERACTIONS + CONTRAINDICATIONS

A

Warfarin, phenytoin and methotrexate can lead to increased plasma levels

CONTRAINDICATIONS:

Newborns & infants < 2 months (kernicterus) – drugs compete with bilirubin for binding sites on albumin

17
Q

TRIMETHOPRIM

A

Structurally similar to folic acid

• Bacteriostatic against Gram-positive & Gram-negative organisms

MOA:

1) Potent inhibitor of bacterial dihydrofolate reductase
2) Inhibits purine, pyrimidine & amino acid synthesis

18
Q

TRIMETHOPRIM CLINICAL APPLICATIONS

A

1) UTI’s
2) BACTERIAL PROSTATITIS (after Ciprofloxacin)
3) BACTERIAL VAGINITIS

19
Q

TRIMETHOPRIM PK + AE

A
  • Mostly (80-90%) excreted unchanged through kidney
  • Reaches high concentrations in prostatic & vaginal fluids

AE:

  • Antifolate effects (contraindicated in pregnancy)
  • Skin rash, pruritus
20
Q

COTRIMOXAZOLE

A
  • Combination of trimethoprim & sulfamethoxazole
  • Bactericidal

Mechanism of action

• Synergistic: inhibition of sequential steps in tetrahydrofolic acid synthesis

21
Q

COTRIMOXAZOLE CLINICAL APPLICATIONS

A

1) Uncomplicated UTI’s (drug of choice)

2) PCP (drug of choice)
3) Nocardiosis (drug of choice)

4) Toxoplasmosis (alternative drug)

• Respiratory, ear, sinus infections (H.influenzae, M.catarrhalis)

22
Q

COTRIMOXAZOLE AE + PK

A
  • Oral admin. generally (can be given IV)
  • Well distributed (including CSF)

ADVERSE EFFECTS:

• Dermatologic (common)

  • GI
  • Hematologic (hemolytic anemia)
  • AIDS patients = higher incidence
  • Contraindicated in pregnancy (esp. *1st trimester)*
23
Q

METRONIDAZOLE

A
  • Antimicrobial, amebicide & antiprotozoal
  • Activity against anaerobic bacteria (including bacteroides & Clostridium)

• Bactericidal

MOA:

  • Anaerobic conditions are vital for optimal activity
  • Undergoes reductive bioactivation of its nitro group by

ferredoxin

• Forms cytotoxic products that interfere with nucleic acid synthesis

24
Q

METRONIDAZOLE CLINICAL APPLICATIONS

A

1) C.difficile infections (drug of choice)
2) Anaerobic or mixed intra-abdominal infections
3) Vaginitis (trichomonas & bacterial vaginosis, G.vaginalis)

4) Brain abscesses
5) H.pylori eradication (in combination)

25
Q

METRONIDAZOLE PK + AE

A
  • Oral, IV, rectal or topical
  • _Wide distribution (including CSF) ****_

• Elimination = hepatic metabolism

AE:

• GI irritation, stomatitis, peripheral neuropathy (prolonged use)

Headache, dark coloration of urine

Leukopenia, dizziness, ataxia (rarer)

• Opportunistic fungal infections

-Disulfiram-like effect (avoid alcohol)

-Use generally not advised in *1st trimester*

26
Q

NITROFURANTOIN

A

URINARY ANTISEPTIC

• Oral agents with antibacterial activity in urine but little or

no systemic effect

  • Use is limited to prophylaxis and treatment of lower UTI’s
  • Bacteriostatic & bactericidal
  • Active against many Gram-positive and Gram-negative bacteria

MOA:

• Reduction of nitrofurantoin by bacteria in the urine leads

to formation of reactive intermediates that subsequently

damage bacterial DNA

• Slow emergence of resistance and no cross-resistance

27
Q

NITROFURANTOIN PK + AE

A

URINARY ANTISEPTIC

Pharmacokinetics

• Rapid elimination (only achieves adequate concentrations in urine)

Adverse Effects

  • Anorexia, nausea & vomiting.
  • Neuropathies, hemolytic anemia (G6PD deficient patients)

PHARM MIDTERM2 (18 decks)

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