CH3 | Protein Synthesis Inhibitors (Tetracyclines) Flashcards
List the tetracyclines.
- Tetracycline (prototype).
- Minocycline.
- Doxycycline (newer agent).
- Demeclocycline (newer agent).
What is the mechanism of action of tetracyclines?
Tetracyclines bind reversibly to the 30S subunit of the bacterial ribosome; exhibiting a bacteriostatic effect.
How do tetracyclines enter bacterial cells?
In part by passive diffusion and an energy-dependent active transport (inner cytoplasmic membrane).
What is the antibacterial spectrum of tetracyclines?
Considered to be broad-spectrum bacteriostatic antibiotics for:
- Gram-positive bacteria.
- Gram-negative bacteria.
- Protozoa.
- Spirochetes.
- Mycobacteria.
What conditions are tetracyclines used to treat?
- Acne.
- Chlamydia.
What are the bacterial resistance mechanisms to tetracyclines?
- Increased drug efflux or decreased drug influx.
- Production of tetracycline-blocking proteins.
- Enzymatic inactivation.
How are tetracyclines absorbed?
Adequately after oral administration.
How are doxycycline and minocycline administered?
Orally and IV.
How should tetracyclines be taken?
On an empty stomach. Dairy products or divalent/trivalent cations should be avoided.
Where do tetracyclines concentrate?
- Most body fluids.
- Bile.
- Liver.
- Kidney.
Why should tetracyclines be avoided in pediatrics and children?
Tetracyclines bind to tissues undergoing calficiation.
How do tetracycline use relate to pregnant women?
Tetracyclines cross the placental barrier and concentrate in fetal bones and dentition.
Which tetracyclines achieve therapeutic CSF levels?
- Minocycline.
- Doxycycline.
How is tetracycline (drug) eliminated?
Unchanged in the urine.
How is minocycline eliminated?
Undergoes hepatic metabolism and renal metabolism (to a lesser extent).
How is doxycycline eliminated?
Via the bile, into the feces.
What are the adverse effects of tetracyclines?
- GIT disturbances.
- Drug deposition in bones and teeth; dangerous to children.
- Hepatotoxicity.
- Phototoxicity (sunburn).
- Vestibular dysfunction.
- Benign intracranial HTN (headaches; blurred vision) (rare).
- Contraindicated in: Pregnant and breastfeeding women, and children less than 8 years of age.
Which tetracyclines have a higher risk of phototoxicity?
- Tetracycline.
- Demeclocycline.
Wear adequate sun protection.
Which tetracyclines have a higher risk of vestibular dysfunction?
Minocycline.
