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Pharm Test 5 > Antibiotics III > Flashcards

Antibiotics III Flashcards

0
Q

Tetracyclines (2)

A

doxycycline, tigecycline

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1
Q

Aminoglycosides (4)

A

Gentamicin, Streptomycin, amikacin, neomycin

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2
Q

Macrolides (2)

A

Erythromycin, azithromycin

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3
Q

2 subunits of bacterial 70S ribosome are:

A

30s and 50S

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4
Q

Aminoglycosides are lipid/water soluble and are given Orally/IV

A

Water soluble, given IV

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5
Q

Gentamicin is bactericidal/bacteriostatic against G+/G- organisms?

A

Bactericidal, G- (and G+ staph); activity is concentration dependent

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6
Q

Why are aminoglycosides not effective against strict anaerobes?

A

Passive diffusion through outer membrane porins into periplasmic space; active transport across the plasma membrane into the cytosol is O2-dependent. Transport is enhanced by cell wall inhibitors.

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7
Q

Aminoglycosides binds to the 30S/50S ribosomal subunit? What does this cause?

A

30S: 1) Interference with formation of the initiation complex. 2) Misreading of mRNA, causing incorrect incorporation of amino acids into proteins. 3) Blockade of translocation inducing premature termination of protein synthesis.

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8
Q

T/F: Aminoglycosides have residual activity for several hours after plasma levels fall below MIC.

A

True: Long post-antibiotic effect

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9
Q

Streptomycin main use

A

Second line drug for active TB

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10
Q

Amikacin main use

A

Least susceptible to inactivation; used in hospitals where resistance to gentamicin and tobramycin is common

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11
Q

Neomycin main use

A

combined in an OTC topical ointment (Neosporin) with polymyxin B and bacitracin

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12
Q

Adverse reactions of Aminoglycosides

A

Ototoxicity (Irreversible-Elevated trough plasma levels impede egress out of inner ear cells, Tinnitus is a warning symptom), Nephrotoxicity (reversible), Neuromuscular blockade.

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13
Q

T/F: with Aminoglycosides, it is better to give a single high dose?

A

True: Less trough time

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14
Q

Mechanism of action for Tetracyclines

A

Active transport system causes drug accumulation in bacterial cells (mammalian cells lack this transport). Binds 30S ribosomal subunit; inhibits binding of tRNAs to the A-site of the mRNA-ribosomal complex-prevents addition of amino acids: Bacteriostatic

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15
Q

Resistance to tetracyclines

A

Due to increased drug efflux and production of proteins that interfere with drug binding to the 30S subunit. Tigecycline renders resistant to efflux and increases binding

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16
Q

Tetracycline are all orally effective except for ________ and they form chelates with multivalent cations. Which cations?

A

Tigecycline, Ca2+, Mg2+, Fe2+, Zn2+, AL3+ Should not be administered with dairy products, iron supplements, MG-containing laxatives and antacids, and bismuth subsalicylate

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17
Q

Therapeutic uses of tetracyclines

A

Broad spectrum agaisnt aerobic and anaerobic G+ and G-. Effective against rickettsial infections. Oral treatment of acne and periodontal disease. Treatment and prophylaxis of malaria.

18
Q

Tetracyclines adverse reactions

A

GI irritation, deposition in bones and teeth, renal toxicity, super infection, hepatotoxicity, photosensitivity

19
Q

MOA of Macrolides

A

Bacteriostatic, but can be bactericidal. Binds to 50S subunit; inhibits translocation step of protein elongation

20
Q

Resistance of macrolides

A

Efflux transporters, plasma-encoded methylation of 50S subunit that decreases binding affinity; induction of erythromycin ribosome methylation (erm) gene confers a multi-drug resistance phenotype referred to as MLSb

21
Q

How are macrolides administered and erythromycin is eliminated primarily by hepatic ________ (enzyme)

A

Administered orally, CYP3A4 (interaction exist)

22
Q

Therapeutic uses of macrolides

A

Commonly used agents and a substitute for penicillin sensitive patients. Atypical pneumonias (Legionnaire’s disease, mycoplasma, chlamydial) and other resp. infections. Bordetella pertussis, diptheria, chlamydia

23
Q

Adverse reactions of macrolides

A

Generally safe. GI irritation, cholestatic hepatitis with erythromycin, prolonged Q-T interval

24
Q

MOA of Clindamycin

A

Binding site overlap at 50S; blocks peptide bond formation through interactions at the A-site and the P-site.

25
Q

T/F: Clindamycin is effective against most anaerobic bacteria and G+ aerobes?

A

True

26
Q

Therapeutic uses of Clindamycin

A

Usually bacteriostatic but can be bactericidal depending on dose, used as alternative to penicillin; not in combo with macrolides or chloraamphenicol. Severe group A streptococcal infections and gas gangrene. Abdominal and pelvic infections caused by Bacteroides fragilis. Topical for acne.

28
Q

Adverse reaction for clindamycin

A

Diarrhea (C. dif)

29
Q

MOA of chlorampenicol

A

1) Binds to peptidyl transferase of the 50S subunit; prevents attachment of incoming tRNA to the A-site (like clindamycin)
2) Broad spectrum Bacteriostatic against G+ (MRSA), G- and anaerobes
3) Widely distributed in tissues, metabolized by liver

30
Q

Resistance to chloramphenicol is due to…

A

acetyltransferase that acetylates (inactivates) the drug

31
Q

Therapeutic use of chloramphenicol

A

Only for life-threatening situations (bacterial meningitis) when other (safer) drugs are ineffective; still used in developing countries because of low cost

32
Q

Name the drug with these adverse conditions:

1) Gray baby syndrome
2) Bone marrow suppression
3) Aplastic anemia

A

Chloramphenicol

33
Q

Name an Oxizolidinone

A

Linezolid

34
Q

MOA of Linezolid

A

Binds to unique site on 23S rRNA of the 50S subunit and blocks formation of the initiation complex; action is bacteriostatic

35
Q

Therapeutic uses of linezolid

A

Effective against MDR G+ pathogens- VRE and MRSA

36
Q

Blood counts should be performed weekly for patients on linezolid because

A

it causes reversible myelosuppression; neuropathy

37
Q

Name a streptogramin

A

Quinupristin-dalfopristin (30-70 fixed dose that is bactericidal)

38
Q

T/F: Quinupristin directly inhibits peptidyl transferase center of the 23S rRNA (50S) and Dalfopristin binds at the same site as the macrolides

A

False: Switched

39
Q

T/F: Quinupristin-dalfopristin is active against many G+ organisms but G- activity is limited and approved by FDA in 1999 for serious infections caused by VRE

A

True

40
Q

Adverse reactions of Quinupristin-dalfopristin

A

Hyperbilirubinemia and arthralgia/myalgia

-Inhibits CYP3A4

41
Q

Drugs that target 50S ribosomal subunit (5)

A 
1-Erythromycin
2-Chloramphenicol
3-Clindamycin
4-Quinupristin-dalfopristin
5-Linezolid
42
Q

Drugs that target 30S ribosomal subunit (2)

A

Aminoglycosides and tetracyclines

43
Q

All of the protein synthesis inhibitors are bacteriostatic except which 2?

A

Aminoglycosides and Quinupristin-dalfopristin

Pharm Test 5 (8 decks)

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