34.tetracyclines

Question 1

name medications that belong to tetracyclines

Answer 1

1. tetracycline - caps. 250mg, flac
2. oxytetracycline - caps.250mg
3. doxycyclin (vibramycin) - caps.100mg

Question 2

Mechanism of action of tetracyclines

Answer 2

1.concentrate intracellularly in susceptible organisms
2.bind reversibly to 30S subunit of bacterial ribosome -
prevent tRNA binding to mRNA -
inhibiting the bacterial protein synthesis

Question 3

antibacterial spectrum of tetracyclines

Answer 3

=.bacteriostatic
against a wide variety of organism -
1.gram +
2.gram -
3.protozoa
4.spirochetes
5.mycobacteria
6.against chlamydia infections

Question 4

how does a resistance to tetracyclines form?

Answer 4

1. efflux pump expels drug out of the cell, thus preventing intracellular accumulation

OR

2. enzymatic activation of the drug and production of bacterial proteins that prevent tetracyclines from binding to the ribosome

Question 5

Pharmacokinetics of Tetracyclines
-absorption

Answer 5

1.adequately absorbed after oral administration
2.if given with divalent or trivalent cations (iron supplements) - decreased absorption, due to formation of nonabsorbable chelates

Question 6

PK - distribution of tetracyclines

Answer 6

1. concentrate well in bile, liver, kidney, gingival fluid and skin
2. bind to tissues undergoing calcification (teeth and bones)
   or to tumors that have a high calcium content
3. penetration into most body fluids is adequate
4. cross placental barrier and concentrate in fetal bones and dentition

Question 7

Metabolism and Elimination of Tetracyclines

Answer 7

1.tetracycline and doxycycline are not hepatically metabolized
2.tetracycline is eliminated unchanged in the urine
3.doxycycline is eliminated via the bile into feces (preferred in renal failure)

Question 8

Adverse effects of Tetracyclines

Answer 8

1. Gastric discomfort - take on empty stomach!
2. discoloration and hypoplasia of teeth
3. temporary stunting of growth
   —limited use in pediatrics
4. hepatotoxicity in high doses - in pregnancy/patients with renal dysfunction
5. phototoxicity: severe sunburn may occur
6. vestibular dysfunction: dizziness, vertigo
7. pseudotumor cerebri: benign, intracranial hypertension with headache and blurred vision

Question 9

Contraindications for Tetracyclines

Answer 9

1.pregnancy, breastfeeding
2.children under 8

Question 10

Doxycycline is an …

Answer 10

enzyme inhibitor

Question 11

Application of tetracyclines for which disease

Answer 11

wide
1-chlamydia
2-lyme disease
3-skin infections
4-RTI
5-STI

Question 12

Tetracyclines are bacteriostatic or cidal
how do they act

Answer 12

bacteriostatic - bind to 30S ribosomal subunit

Question 13

how are tetracyclines administered?

Answer 13

1.orally
2.parenterally
3.topically

Question 14

what happens when tetracyclines are administered per i.v?

Answer 14

increased risk of phlebitis