PHM203 - Protein Synthesis Inhibitors: Questions With
Correct Solutions
What effect is possible with protein synthesis inhibitors? Right Ans - Post-
antibiotic effect
What two subunits combine to form a 70S ribosome? What is the function of a
ribosome? Right Ans - 30S and 50S. It is the workbench for protein
synthesis.
Which two antibiotics bind to mammalian ribosomes? Right Ans -
tetracyclines and chloramphenicol
What are the 5 classes of protein synthesis inhibitors? Right Ans -
Macrolides (erythromycin)
Oxazolidinones (linezolid)
Clindamycin
Aminoglycosides (gentamicin, tobramycin)
Tetracyclines (tetracycline, doxycycline)
They act at initiation, translation, and elongation
Which ribosomal subunit do macrolides bind to? Right Ans - 50S,
reversibly.
What are the three macrolides? Right Ans - Azithromycin (IV and po)
Clarithromycin (only po)
Erythromycin (po, rarely used)
Classify azithromycin, erythromycin and clarithromycin from longest to
shortest half life.
Which two are extensively metabolized by the liver (CYP450)? Right Ans -
Azythro>clarithro>erythro
CYP450: Ery>clarith
Macrolides adverse effects Right Ans - Primarily with erythromycin
- GI (N/V/D)
, - Tinnitus, hearing loss
- QT-prolongation - DI
- CYP450 inhibitor (theophylline, cyclosporine)
GI heard that QT is prolonged
What are the 3 mechanisms of resistance for macrolides? What do they cross
resist with? Right Ans - - Reduced cell membrane permeability or active
efflux
- Production of esterases that hydrolyze macrolides
- Modification of ribosomal binding site by chromosomal mutation or by a
methylate
There is cross-resistance with MLSb (macrolides, lincosomides,
streptogramins) and with clindamycin
What is the spectrum of macrolides? Right Ans - - S. pneumoniae (GP)
- GN
- Atypical organisms of pneumonia
- H. influenzae (clarithromycin and azithromycin)
Which ribosomal subunit does clindamycin bind to Right Ans - 50S,
reversibly
What kind of drug is clindamycin? Does it penetrate well into all tissues?
Right Ans - It is a pro-drug (both IV and oral)
Penetrates well into tissue except the brain! (40% will cross BBB)
Does clindamycin need to be adjusted for renal dysfunction? Is it metabolized
by CYP450? Right Ans - No
What are the adverse effects of clindamycin? Right Ans - N/V/D
C. difficile
Transient elevation in liver enzymes
Neuromuscular blockade
What does clindamycin cross resist with Right Ans - Macrolides - MLSb
What are the 3 mechanisms of resistance for clindamycin? Right Ans - -
Mutation of the ribosomal receptor site (50S)
Correct Solutions
What effect is possible with protein synthesis inhibitors? Right Ans - Post-
antibiotic effect
What two subunits combine to form a 70S ribosome? What is the function of a
ribosome? Right Ans - 30S and 50S. It is the workbench for protein
synthesis.
Which two antibiotics bind to mammalian ribosomes? Right Ans -
tetracyclines and chloramphenicol
What are the 5 classes of protein synthesis inhibitors? Right Ans -
Macrolides (erythromycin)
Oxazolidinones (linezolid)
Clindamycin
Aminoglycosides (gentamicin, tobramycin)
Tetracyclines (tetracycline, doxycycline)
They act at initiation, translation, and elongation
Which ribosomal subunit do macrolides bind to? Right Ans - 50S,
reversibly.
What are the three macrolides? Right Ans - Azithromycin (IV and po)
Clarithromycin (only po)
Erythromycin (po, rarely used)
Classify azithromycin, erythromycin and clarithromycin from longest to
shortest half life.
Which two are extensively metabolized by the liver (CYP450)? Right Ans -
Azythro>clarithro>erythro
CYP450: Ery>clarith
Macrolides adverse effects Right Ans - Primarily with erythromycin
- GI (N/V/D)
, - Tinnitus, hearing loss
- QT-prolongation - DI
- CYP450 inhibitor (theophylline, cyclosporine)
GI heard that QT is prolonged
What are the 3 mechanisms of resistance for macrolides? What do they cross
resist with? Right Ans - - Reduced cell membrane permeability or active
efflux
- Production of esterases that hydrolyze macrolides
- Modification of ribosomal binding site by chromosomal mutation or by a
methylate
There is cross-resistance with MLSb (macrolides, lincosomides,
streptogramins) and with clindamycin
What is the spectrum of macrolides? Right Ans - - S. pneumoniae (GP)
- GN
- Atypical organisms of pneumonia
- H. influenzae (clarithromycin and azithromycin)
Which ribosomal subunit does clindamycin bind to Right Ans - 50S,
reversibly
What kind of drug is clindamycin? Does it penetrate well into all tissues?
Right Ans - It is a pro-drug (both IV and oral)
Penetrates well into tissue except the brain! (40% will cross BBB)
Does clindamycin need to be adjusted for renal dysfunction? Is it metabolized
by CYP450? Right Ans - No
What are the adverse effects of clindamycin? Right Ans - N/V/D
C. difficile
Transient elevation in liver enzymes
Neuromuscular blockade
What does clindamycin cross resist with Right Ans - Macrolides - MLSb
What are the 3 mechanisms of resistance for clindamycin? Right Ans - -
Mutation of the ribosomal receptor site (50S)
