Quiz 3 - Smith - Antimicrobials II

Question 1

Difference b/t prokaryotic and eukaryotic ribosome.

Answer 1

Pro - 70 S = 30 S + 50 S

Eu - 80 S = 40 S + 60 S

*S is a Svedberg unit and is a fx of sedimentation rate, which is effected by both molecular weight and shape

Question 2

What is dose-dependent selectivity?

Answer 2

At low pharmacological doses, antimicrobial PSI’s (Protein synthesis inhibitors) are MORE SELECTIVE for bacterial ribosomes, so LESS TOXIC

At higher doses, toxicity occurs due to reduced selectivity
-Both host and bacterial ribosomes are affected, esp mitochondria
—Chloramphenicol
–Tetracyclines

Question 3

What does the A site do?

P site?

E site?

Answer 3

A - Holds AA to be added

P - Holds growing polypeptide chain

E - Exit site for tRNA

Question 4

Tell me how translation works?

Answer 4

When appropriate tRNA is recognized, a peptide bond is formed b/t the AA in the P-site and the AA in the A-site

String of AAs at the P site transfers to the AA in the A site

Ribosome shifts down the mRNA one codon and process repeats

tRNA in the P-site is shifted to the E-site and ejected from the ribosome

Process continues until a stop codon is positioned in the A-site

Question 5

What class are the following drugs in?

Gentamycin

Amikacin

Tobramycin

Streptomycin

Neomycin

Answer 5

Aminoglycosides

*Cephalosporins are typically used before these due to toxicity risks

Question 6

How do aminogylcosides work?

Answer 6

Bind to the 30S subunit and change its shape which does 3 things

• Block initiation
• Early termination
• Misreading

*THEY TARGET THE 30S subunit

Question 7

Tell me about streptomycin (IM, IV).

Answer 7

Oldest aminoglycoside

High level of bacterial resistance

Question 8

Gentamycin (IV) - tell me about it.

Answer 8

MOST COMMONLY PRESCRIBED aminoglycoside

Question 9

Tell me about amikacin (IM, IV).

Answer 9

Broadest spectrum

-Diarrhea

Question 10

Tell me about tobramycin (IM, IV).

Answer 10

Excellent against Pseudomonas aeruginosa

Question 11

Tell me about neomycin (Topical only).

Answer 11

Very toxic

Topical
Enema before bowel surgery

Question 12

When should aminoglycosides be used?

Answer 12

Against aerobic G- infections, like Pseudomonas

*Prone to high toxicity rates

Once daily dosing is very common

Question 13

T/F - Aminoglycosides are given IV or IM, mostly.

Answer 13

TRUE

NOT oral

*Exception is neomycin which is topical

**Risk of nephrotoxicity and ototoxicity is conc. Dependent

Question 14

Aminoglycosides synergize greatly with what two other classes?

Answer 14

B-LACTAMS

VANCOMYCIN

Question 15

Tell me about ototoxicity.

Answer 15

Correlates with the # of destroyed hair cells

• Usually irreversible
• Streptomycin is linked to vertigo and loss of balance

Question 16

Tell me about nephrotoxicity.

Answer 16

Usually reversible

Dose-dependent

-Frequent plasma conc and kidney fx monitoring is essential

Question 17

What are 4 adverse effects of aminoglycosides?

Answer 17

Ototoxicity

Nephrotoxicity

Neuromuscular paralysis

Teratogenic - Don’t give to pregnant women

*Also, contact dermatitis

Question 18

What are the “at risk groups” of aminoglycosides?

Answer 18

Elderly

Impaired renal fx

Septic pts

Recent exposure to other aminoglycosides
-Post-antibiotic effect can occur

Question 19

What 4 drugs are in the tetracycline family?

Answer 19

Tetracycline

Doxycycline

Minocycline

Tigecycline

Question 20

T/F - Tetracylcine is good against acne.

Answer 20

TRUE

Question 21

T/F - Tetracyclines are broad spec and affect G- and G+.

Answer 21

TRUE

Question 22

What is the exception to the rule with these drugs?

Answer 22

Tigecycline

-Effective even in pts resistant to other TTCs

Question 23

How do tetracyclines work?

Answer 23

Reversibly binds to 30S of bacterial ribosome blocking access of the amino acyl-tRNA to the mRNA-ribosomes complex’s acceptor site

Question 24

What are the pharmacokinetics of tetracyclines?

Answer 24

Oral absorption altered by diary, iron supplements or antacids

DO NOT USE DURING PREGNANCY OR BREAST FEEDING

USED FOR TREATMENT OF ACNE VULGARIS

Question 25

What are two oral adverse effects of tetracyclines?

Answer 25

Hairy tongue

Deposition in bone and primary dentition

Question 26

What are some general adverse effects of tetracyclines?

Answer 26

GI upset

Disulfiram-like effect - Avoid alcohol use while taking tetracyclines- hungover

Headache

Vestibular problems - dizziness, nausea, vomiting

Question 27

Tigecycline was developed for what?

Answer 27

To overcome tetracycline resistance in complicated skin, soft tissue, and intra abdominal infections

Know that this was created for those allergic to tetracyclines

Administered IV

Question 28

Erythromycin

Clarithromycin

Azithromycin

Are all what?

Answer 28

Macrolides or ketolides

Question 29

What is the mechanism of macrolides?

Answer 29

Irreversibly binds to the 50S subunit of bacterial ribosome to inhibit the translocation step of protein synthesis (From the A site to the P site)

BROAD SPEC

Cross resistant w/in class

Question 30

Tell me what macrolides are used for?

Answer 30

URIs and CA-pneumonia

Good alternative for pts allergic to penicillin

Question 31

Tell me about erythromycin.

Answer 31

Largely been replaced by clarithromycin and azithromycin for CA-pneumonia

Used for G+ bacteria, spirochetes, n gonorrhea, chlamydia, mycoplasma, legionella

Question 32

Tell me about clarithromycin.

Answer 32

Same as erythromycin plus add’l activity against h influenzae and h pylori

Question 33

Tell me about azithromycin.

Answer 33

Z-pack

Less active against staph and strep than erythromycin

More active against respiratory infections due to h influenzae, moraxella catarrhalis and mycobacterium (NTB)

LONGEST HALF-LIFE AND VOLUME OF DISTRIBUTION IN THIS CLASS