Pharmacology - Antibiotics Flashcards
Trimethoprim
Inhibits dihydrofolate reductase (prevents reduction of folic acid to tetrahydrofolate)
Sulfamethoxazole
Structural analog of para-aminobenoic acid (PABA). Competes with PABA to inhibit dihydrofolic acid synthesis, an intermediate step in formation of tetrahydrofolate.
Imipenem
Binds a PBP (penicillin binding protein) and inhibits final step of peptidoglycan synthesis in bacterial cell walls.
Cilastatin
Use in conjunction with imipenem - prevents renal metabolism of imipenem by competitively inhibiting dehydropeptidase in renal tubule brush border.
Remember: Imipenem is LASTING with CiLASTatin.
Bacitracin
Prevents mucopeptide transfer into growing cell wall, inhibiting cell wall synthesis.
Metronidazole
Binds DNA in susceptible cells, unraveling DNA’s helical structure and breaking its strands.
Pyrimethamine
Acts the same way as trimethoprim and methotrexate; treats toxoplasmosis because it inhibits parasitic dihydrofolate reductase.
Penicillins and cephalosporins
Irreversibly bind penicillin binding proteins, AKA transpeptidases, which cross-link peptidoglycan in the bacterial cell wall.
NOTE: They do NOT bind to the cell wall glycoproteins! They bind to the transpeptidases!
Another word for penicillin binding proteins?
Transpeptidases!
What do transpeptidases do?
They cross-link peptidoglycan in the bacterial cell wall.
Vancomycin
Binds to terminal D-alanine residues of cell wall glycoproteins and prevents transpeptidases from forming cross-links.
Note: Vancomycin actually binds to the glycoproteins of the cell wall.
Side effects: Red man syndrome (histamine mediated), nephrotoxicity
Which binds to cell wall glycoproteins, vanc or penicillins?
Vancomycin
Fluoroquinolones
Interfere with DNA replication by binding to DNA gyrase
Beta lactamase
Degrades penicillin and cephalosporin.
Which antibiotics would require entry into the cell to function?
Tetracycline and macrolides for example - probably things that inhibit ribosomal assembly.
What are the commonly used drugs for invasive MRSA?
- Vancomycin
- Daptomycin
- Linezolid
Remember: My Dapper Van is Lined with MRSA.
Daptomycin
Disrupts bacterial membrane through creation of transmembrane channels which cause leakage of intracellular ions, leading to depolarization of the cellular membrane and inhibition of DNA / RNA / protein synthesis.
Cannot permeate outer membrane of Gram Negative bacteria.
Is inactivated by pulmonary surfactant - do not use for pneumonieas.
Side effects: increased CPK and increased myopathy, especially in patients taking statins.
Linezolid
Inhibits bacterial protein synthesis by binding to the 50S subunit.
Basically like clinda.
Side effects: Thrombocytopenia, optic neuritis, high risk for serotonin syndrome.
Tetracyclines
Inhibit 30S subunit.
Bacteriostatic, bind to 30S and prevent attachment of amino-acyl tRNA; limited CNS penetration. Do not take with milk.
Remember: Buy AT 30, CCEL at 50.
Aminoglycosides
Bactericidal - inhibit formation of initiation complex and cause misreading of mRNA; also block translocation. Require O2 for uptake; therefore ineffective against anaerobes.
Mean GNATS caNNOT kill annaerobes.
Gentamicin Neomycin Amikacin Tobramycin Streptomycin
Nephrotoxic
Neuromuscular blockade
Ototoxic
Teratogenic
Macrolides
Azithromycin, clarithromycin, erythromycin. Inhibit protein synthesis by blocking translocation. bind to 23S rRNA of the 50S ribosomal subunit. bacteriostatic.
Chloramphenicol
Binds peptidyltransferase at 50S ribosomal subunit. bacteriostatic. Aplastic anemia and gray baby syndorme.
MOR: Plasmid-encoded acetyltransferase inactivates drug.
Clindamycin
Blocks peptide transfer at the 50s ribosomal subunit.
Carbapenems
Imipenem, meropenem, ertapenem, doripenem
beta lactam / broad spectrum / beta-lactamase resistant
