Dr. Roane Macrolides, Clindamycin, Linezolid, etc Flashcards
Macrolide MOA
-Macrolides and Clindamycin probably share the same MOA
-binding to the 50S subunit and inhibiting ribosome translocation
Macrolides
Azithromycin
Erythromycin
Clarithromycin
Which drug class shares the same MOA with Macrolides?
Clindamycin
Spectrum of Activity
-Broad spectrum
-Gram (+): Staph, Strep
-Gram (-)
-Syphilis
-Chlamydia
-Mycoplasma Pneumonia
Which pneumonia is referred to as “walking” pneumonia?
Mycoplasma pneumonia - not so sick so pt can walk
-considered atypical -> Erythromycin and tetracyclines are effective
Which of the Macrolides has the longest half-life?
Azithromycin 40 hrs
Zpak PO
What causes high levels of drugs when a patient takes Chloramphenicol?
Erythromycin and Clarithromycin inhibit CYP450
CYP450 cant metabolize other drugs -> increase in concentration
What is a prokinetic effect?
Stimulation of gastric motility (Erythromycin)
Adverse effects of Macrolides
-GI disturbance, cramping -> used in Erythromycin (prokinetic effect)
-Cholestatic Jaundice
-Ototoxicity
What is a QTc?
calculated average interval between Q-wave and T-wave
Which Microlide is associated with prolongation of the QTc interval?
Telithromycin (Ketek)
Consequence of QT prolongation
-Increased risk of heart attack
-Torsades de pointes (twisting of points)
Which Macrolide treats Pseudomembranous colitis (superinfection) of the colon due to overgrowth of C. diff?
Fidaxomicin (Dificid)
Why is the Activity of Fidaxomicin limited to the colon?
Due to its poor oral availability
What is the resistance mechanism of bacteria against Macrolides?
Erythromycin ribosome methylation ERM genes: ERMa ERMb responsible for:
-methylation of the ribosomal binding site -> prevention of binding
-Efflux pump
What is the purpose of the D-test?
-Do Macrolides induce resistance to Clindamycin?
-it depends on if the ERM gene coding for MLS is ON -> it methylates ribosomal RNA preventing binding of macrolides, clindamycin, and streptogramins
-It affects the activity of Clindamycin bc they share the same MOA
What are the semisynthetic drugs derived from Streptogramins?
Quinupristin/dalfopristin (Synercid)
What is the MOA of Quinupristin/dalfopristin?
-Binding to separate sites of the 50S ribosome -> synergistic effect to inhibit protein synthesis
-long-lasting post-antibiotic effect (PAE)
Which CYP is affected by Quinupristin/dalfopristin?
CYP 3A4
Oxazolidinones
-Linezolid (Zyvox)
-Tedizolid (Sivextro
-chemical synthesized
Linezolid MOA
Inhibits the formation of 70S
->Blocks assembly of the initiation complex
Linezolid shares the MOA with which drug?
-Chloramphenicol
-blocking peptide bond formation
-Resistance due to altering the binding site
What is an important indication of Linezolid?
-ABSSSI (Acute Bacterial Skin and skin structure infection)
-alternative to Vancomycin
Why does Linezolid have such a high number of drugs it interacts with?
Because it blocks MOA (monoamine oxidase)
MOA is responsible for metabolizing a variety of drugs into their inactive form
