Tetracyclines (and Tigecycline)

Tertracyclines and tigecycline

16 cards | Total Attempts: 190 | Created by slhecht | Last updated: Sep 30, 2015 | Total Attempts: 190

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What Is The Core Structure Of Tetracyclines?

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Cards In This Set

Front	Back
What is the core structure of tetracyclines?	Four fused 6-membered rings (tetra-cycline).
What is the main structural modification to the tertracycline structure that yields tigecycline?	Glycoamino complex.
How do tetracyclines (and tigecyline) work?	They inhibit protein synthesis by binding to the 30S bacterial ribosomal subunit.Note: Tigecyline binds more strongly
Tetracyclines used to be considered broad-spectrum antibiotics. What changed?	Widespread resistance limits their use.
Are tetracyclines (and tigecyline) bactericidal or bacteriostatic?	Bacteriostatic.
What are mechanisms of resistance to tetracyclines? What about tigecycline?	1. EFFLUX (main mechanism): both Gram+ and Gram- can synthesize large amounts of efflux proteins2. Ribosomal Protection Proteins: bacteria can produce proteins that bind to the ribosome, causing a conformational change so that tetracylines can not longer bind.3. Decreased penetration across bacterial membrane Tigecycline is less susceptible to resistance; tet-resistant organisms are susceptible to tigecycline.
How are tetracyclines administered and absorbed? What about tigecycline?	Tetracyclines are administered orally, with variable absorption. Absorption is impaired by di-and trivalent cations, e.g. Ca²⁺ (don't take with milk), Mg²⁺, Al³⁺ (component of antacids). Tigecycline is administered by IV.
How is tetracycline distributed in the body?	Sequestered in tissues, usually liver. This means Vd can be bigger than body water. Concentration in CSF is low.
How are tetracyclines metabolized and eliminated?	Tetracyclines are concentrated in the liver. Primary elimination route varies: - Doxycycline and minocycline ("domino") eliminated hepatically. Use these for renal failure patients.- Demeclocyline and tetracycline eliminated renally Note: t_1/2 of doxycyline (16hrs) is twice as long at t_1/2 of tetracyline (8hrs), which makes doxycyline very popular.
What are tetracyclines used for?	Since broad spectrum activity has been largely compromised by resistance, tetracyclines are good for organisms that lack a cell wall.-- Rickettsiae-- Chlamydiae-- Lyme disease
What are some adverse effects of all tetracyclines?Specific tetracyclines?	1. GI irritation2. Effects on calcifying tissues (they bind Ca2+)-- inhibit bone growth in utero (contraindiated in pregnant women, children <8yo)-- discoloration of teeth3. Hepatotoxicity (especially in pregnant women)4. Decreased efficacy of oral contraceptives5. Can lead to superinfections by broadly killing off flora 6. Democlo- and doxycline can lead to photosensitiviy* ("phoDosensiDivity")7. Minocyclin can lead to dizziness*
What are two reasons tetracycline is contraindicated in pregnant women?	1. Inhibition of fetal bone growth2. Increased susceptibility to hepatotoxicity in both mother and fetus.
Who may not take tetracyclines due to its effect on calcifying tissues?	Pregnant women and children under 8yo.
What are some adverse effects of tigecycline?	FeverGI irritationHypertensionHepatotoxicityHematologic Alphabetical: FGHHH
What are differences between tetracyclines and tigecyline?	Administration: tetracyclines are given orally, tigecycline by IV Efficacy: *tigecyline* binds better to 30S subunit AND evades resistance mechanisms Clinical uses: Tetracyclines have some broad spectrum activity (diminished due to resistance) and are effective against organisms that lack a cell wall. Tigecycline is reserved for complex skin and intra-abdominal infections and drug-resistant organisms. Adverse Effects: lots for tetracyclines, few for tigecyline