Antibiotics that Inhibit Protein Synthesis Flashcards
Why can high levels of antibiotics that inhibit protein synthesis cause toxic effects for humans?
Mammalian mitochondrial ribosome is close to bacterial. High levels of these drugs may cause toxic effects.
Who not to give Tetracyclines to
Pregnant women
Breast feeding
Kids under 8-12
MOA of tetracycline
Reversibly bind to the 30s ribosomal subunit. Prevent binding of tRNA.
Is tetracycline bacteriostatic or cidal?
Static. Will haunt protein synthesis, but not killing.
Each of the Tetracyclines have small differences in efficacy and pharmacokinetics. Which tetracyclines are longer lasting?
Doxycycline and minocycline.
Tetracycline spectrum
Considered broad
Will target gram negative and positive
Which two drugs are used to treat chlamydial infections?
Doxycycline or azithromycin
Tetracycline resistant bacteria may be susceptible to others in class. True or false.
True. In must cases, you don’t want to prescribe within the same class but ok for tetracycline class.
Absorption of tetracycline
Bind to calcium, aluminum, iron, and magnesium. Dairy products reduce bioavailability of tetracycline. Avoid antacids or iron supplements with all in this class.
Distribution of tetracycline
Bind to tissues undergoing calcification- teeth and bones.
Minocycline is the only one to penetrate CSF (but not effective for CNS infections)
Will cross placenta and bind to fetal bones and teeth.
Food + tetracyclines?
Avoid taking with dairy, iron, or antacid.
Take on empty stomach for better absorption.
Elimination of tetracyclines
Most are secreted into bile by the liver–> secreted back into GI –> Reabsorbed into intestine –> excreted by kidney (urine)
Which tetracycline is not eliminated by the kidney AKA which tetracycline should you prescribe to someone with kidney problems
Doxycycline is not eliminated by kidney. Good for patients with renal disease.
Are tetracyclines excreted in breast milk?
Yes, all of them are. Do not give to pregnant women, breastfeeding women, or kids.
Common adverse effects with tetracycline
- Gastric discomfort- avoid dairy and antacids.
- Discoloration and hypoplasia of teeth in children. Can stunt growth.
- Photo-toxicity (severe sunburn)
- Pseudotumor cerebri (headache and blurred vision. Swollen ON bilateral)
- Superinfections
Which drug class can cause pseudo tumor cerebri of bilateral ON
Tetracyclines. May report headaches and blurry vision.
Why would you use low doses of doxycyline?
Show anti-inflammatory effect. Down regulates pro-inflammatory chemicals. very effective at treating soft tissue inflammation (rosacea, blepharitis, possibly dry eye)
50 mg or less. Does NOT encourage resistance to larger dose.
Is ahminoglycosides bacteriostatic or cidal
Primarily bactericidal.
How are ahminoglycosides administered
Usually topically, IV, or IM.
Very polar so oral absorption is inadequate.
Rarely used systemically bc is associated with serious toxicities.
What ingredient are people allergic to in neosporin?
Neomycin (amino glycoside drug)
Which two aminoglycosides can elicit an allergic response?
Gentamicin and neomycin.
Not gentle or nice
Which aminoglycoside usually doesn’t result in an allergic reaction?
Tobramycin
Which drug class results in unchanged drug appearance in the urine?
Aminoglycosides. Very limited metabolism, then eliminated by the kidneys.
Aminoglycosides antibacterial spectrum
Effective against aerobic gram negative bacteria (including pseudomonas)
Effective against some gram positive bacteria. Can be combined with B-lactam or vancomycin to improve spectrum.
How is resistance of ahminoglycosides caused?
Decreased uptake of drug, plasmid associated synthesis of enzymes.
Distribution of aminoglycosides To CNS? Tissues? Renal cortex and inner ear? placenta?
Low penetration to CNS and tissues.
High concentration in renal cortex and inner ear.
All cross the placenta
Metabolism of aminoglycosides
None. Rapidly excreted in urine.
Four main adverse effects of aminoglycosides?
- Ototoxicity. Deafness may be irreversible. Can affect fetus.
- Nephrotoxicity. Kidney damage can be severe.
- Neuromuscular paralysis. Causes decrease in Ach release. Mainly after large dose.
- Allergic reactions. Contact dermatitis very common with neomycin and gentimycin.
Macrolide that was developed as an alternative to penicillin G.
Erythromycin. Good if allergic to PCN.
Drug of choice in macrolide class for chlamydia infections. What is the dose?
Azithromycin. 1000 mg one time!
Can either get a 1000 mg powder or 2 500 mg tablets.
Mechanisms of macrolide resistance
Efflux pumo
Decreased affinity to 50 s subunit
Plasmid associated enzymes.
Which macrolide should not be given IV
Erythromycin. High incidence of thrombophlebitis. Pain and inflammation at injection site.
Macrolide with longest half life, resulting in high volume of distribution
Azithromycin. Great penetration into most tissues, Good for eyelid infections (stye)
Which two macrolides are extensively metabolized and inhibit oxidation of many drugs
Erythromycin and clarithromycin. Cause a lot of drug/drug interactions due to extensive interaction with P450 enzymes.
Macrolide adverse effects
GI problems Acute hepatitis with jaundice Ototoxicity Caution in patients with arrhythmia -azithromycin may be associated with increased risk of cardiac death.
Clindamycin MOA. Commonly used to treat what?
50 S interference.
Can be used to treat skin and soft tissue infections.
Commonly used to treat abdominal infections associated with trauma (usually caused by anaerobic bacteria)
Linezolid used to combat resistant gram ___ organisms
positive.
MOA of linezolid
Inhibits formation of ribosomal complex. Unique binding site means no cross resistance with other drug classes.
bacteria haven’t figured this one out yet.
Pharmacokinetics of Linezolid
Completely absorbed on oral administration
High volume of dis
No interaction with P450
Renal and non-renal excretion
Adverse effets of linezolid
Thrombocytopenia- low platelets
Anemia
Optic and peripheral neuropathy.
Can increase serotonin levels. Caution if patient is taking other antidepressants to increase serotonin levels.
