Anti-Microbials (2) Flashcards
What is the MOA of the tetracyclines?
Bacteriostatic; bind to 30S and prevent attachment of aminoacyl-tRNA; limited CNS penetration.
What antimicrobial can be used in pts with renal failure because it’s fecally elminated?
Doxycycline is fecally eliminated and can be used in patients with renal failure.
bind to 30S and prevent attachment of aminoacyl-tRNA;
Drug used for the following bugs:
Borrelia burgdorferi, M. pneumoniae.
Drugs’ ability to accumulate intracellularly makes them very effective against
Rickettsia and Chlamydia.
Tetracyclines: doxycycline
Why can’t we take tetracyclines with milk, antacids or iron containing drugs?
. Do not take tetracyclines with milk (Ca2+), antacids (Ca2+ or Mg2+), or iron-containing preparations because divalent cations inhibit drugs’ absorption in the gut.
Young woman comes in with Chlyamydia, you prescribe the drug you SHOULD but what do we need to check first
tx Chlymidia with Doxycycline, but it a tetracycline thus teratogenic—make sure she’s not pregnant: see teeth stainig and inhibition of bone growth
Pt comes in with Lymes: Borrellia burgdorferi
What drug do you px and what is the mechanims of resisitance to this?
Px tetracycline: like Doxycycilne
resistance: decreaseud uptake or increased efflux out of bacterial cells by plasmid-endoced transport pumps
Drug with serious sides that can be used for the following:
Meningitis (Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae) and Rocky Mountain spotted fever (Rickettsia rickettsii).
Chloramphenicol
What serious sides effects are associatd with Chloramphenicol?
Anemia (dose dependent), aplastic anemia (dose independent), gray baby syndrome (in premature infants because they lack liver UDP-glucuronyl transferase).
Blocks peptidyltransferase at 50S ribosomal subunit.
Bacteriostatic.
Chloramphenicol
Blocks _peptide transfer (translocation) at 50S ribosomal subuni_t.
Bacteriostatic
Clindamycin
Used for Anaerobic infections (e.g., Bacteroides spp., Clostridium perfringens) in aspiration pneumonia, lung abscesses, and oral infections.
Also effective against invasive group A streptococcal infection
What’s it’s mechanism?
Clindamycin
Blocks peptide transfer (translocation) at 50S ribosomal subunit.
Bacteriostatic.
Inhibit protein synthesis by binding to 50S subunit and preventing formation of the initiation complex.
What serious side effect do we worry about?
Linezolid
Bone marrow suppression (especially thrombocytopenia), peripheral neuropathy, serotonin syndrome.
When would we prescribe Linezolid?
What’s it’s side effect profile?
Gram-positive species including MRSA and VRE
Bone marrow suppression
What is the mechanism of Macrolides?
What drugs are macrolides?
Inhibit protein synthesis by blocking translocation (“macroslides”); bind to the 23S rRNA of the 50S ribosomal subunit. Bacteriostatic
Azithromycin, clarithromycin, erythromycin.
Uses include: Atypical pneumonias (Mycoplasma, Chlamydia, Legionella), STIs (Chlamydia), gram-positive cocci (streptococcal infections in patients allergic to penicillin), and B. pertussis.
Macrolides: azithromycin, clarithromycin, erythromycin
What is the side effect profile of macrolides?
MACRO:
Gastrointestinal Motility issues,
Arrhythmia caused by prolonged QT interval,
acute Cholestatic hepatitis,
Rash,
eOsinophilia.
What specific side effect is seen with clarithromycin and erythromycin?
Clarithromycin and erythromycin inhibit cytochrome P-450.
What is the mechanism of resistance by bugs to Macrolides?
Methylation of 23S rRNA-binding site prevents binding of drug.
MOA of Trimethoprim
Inhibits bacterial dihydrofolate reductase.
Bacteriostatic.
Uses of Trimethoprim
Used in combination with sulfonamides (trimethoprim-sulfamethoxazole [TMP- SMX]), causing sequential block of folate synthesis.
Combination used for UTIs, Shigella, Salmonella, Pneumocystis jirovecii pneumonia treatment and prophylaxis, toxoplasmosis prophylaxis.
Used for UTIs, Shigella, Salmonella, Pneumocystis jirovecii pneumonia treatment and prophylaxis, toxoplasmosis prophylaxis.
Trimpethoprim: blocks dihydrofolate reductase
use with sulfonamide to get sequential blockade of folate synthesis
Negative side effects of Trimpethoprim
Megaloblastic anemia, leukopenia, granulocytopenia. (May alleviate with supplemental folinic acid). TMP Treats Marrow Poorly.
Inhibit folate synthesis. Para-aminobenzoic acid (PABA) antimetabolites inhibit dihydropteroate synthase. Bacteriostatic (bactericidal when combined with trimethoprim).
Sulfamethoxazole (SMX), sulfisoxazole, sulfadiazin
Uses of Sulfonamides: which inhibit folate synthesis:
(PABA antimetabolite to inhibit dihydropteroate synthase)
Gram-positives, gram-negatives, Nocardia, Chlamydia.
Triple sulfas or SMX for simple UTI.
