Pharm - Antibiotics, Antifungals, Antivirals Flashcards
Antimicrobial drugs do not readily enter
CNS, bone, prostate, eye
Narrow spectrum penicillin exemplar
Penicillin V
Penicillin V coverage
non-beta lactamase producing gram+ve cocci, treponema pallidum
Extended spectrum penicillin exemplar
Amoxicillin
Amoxicillin coverage
non-beta lactamase producing gram +ve cocci, gram -ve
Common bacterial infections - OM, strep, second line for UTI
Amoxicillin resistance
- Escherichia d/t upregulation of beta-lactamases
- S pneumoniae - overcome by dose
- Moraxella, haemophilus - overcome by adding beta lactamase inhibitor
Monobactam exemplar
Aztreonam
Aztreonam coverage/ use
- Enhanced against gram -ve bacili, none against gram +ve
- For serious infections w/ resistant bacteria incld. pseudomonas (IV)
Carbapenem exemplar
Meropenem
Meropenem coverage/ use
- Similar to penicillins, larger spectrum of gram +ve and -ve
- resistance is growing
- systemic infections and multidrug resistant (IV)
Cephalosporins coverage
1st gen primarily against gram +ve, later increased gram -ve and decreased gram +ve
First gen cephalosporin exemplar
Cephalexin
Cephalexin use
prior to surgery to eliminate skin flora
Second gen cephalosporin exemplar
Cefuroxime
Third gen cephalosporin exemplar
Ceftriaxone
Ceftriaxone uses
- hospital acquired infections
- can enter CNS - meningitis
- gonorrhea
Fourth gen cephalosporin exemplar
Cefepine
Cefepime uses and drawbacks
- treatment of multi-drug resistant
- associated with higher all cause mortality d/t encephalopathy
Beta lactam adverse effects
- common: N/V, diarrhea, rash, urticaria, superinfections (candida)
- less common: fever, vomiting, erythema, dermatitis, angioedema
- Pseudomembranous colitis d/t c difficile
- allergy/ anaphylaxis/ hypersensitivity
Beta lactam classes
Pencillins, monobactam, carbapenems, cephalosporins
Other cell wall inhibitor classes
UDP-MurNAc inhibitor, Glycopeptide, Beta lactamase inhibitor
Fosfomycin mechanism
- interferes with synthesis of UDP-NAM near the beginning of the peptidoglycan synthesis pathway
- rapidly excreted which creates effectively high urinary levels
Fosfomycin dosing
One large dose as resistance rapidly emerges
Vancomycin mechanism
Binding to end of peptidoglycan and interfering with crosslinking
Vancomycin uses
- serious infections caused by gram +ve drug resistant (IV)
Vancomycin adverse effect
- can cause diffuse flushing and pruritis d/t histamine release (red man syndrome)
Beta lactamase inhibitors exemplar
Clavulanic acid aka clavulanate
Clavulanate mechanism
- inhibits class-A beta lactamases
- No intrinsic antimicrobial activity, but serves as surrogate beta-lactamase substrate when given with another beta lactam antibiotic and protects it from destruction
Common bacterial resistance mechanisms
- production of various classes of beta lactamases
- alteration of structure of penicillin-binding proteins
- changes to porins in outer membrane of gram -ve bacteria
Inhibitors of bacterial protein synthesis classes
- Affect 30s - aminoglycosides, tetracyclines
- Affect 50S - macrolides, other
Aminoglycosides exemplar
Gentamicin
Aminoglycoside mechanism
Bind the 30S subunit and interfere with reading of mRNA code –> insertion of wrong amino acid in peptide chain
irreversible
Gentamicin usage
- active against wide range of grame -ve
- used in combination with penicillin to treat serious infection (bacterial endocarditis)
- IV or topical, measure plasma concentration
- has long post-antibiotic effect
Gentamicin adverse effects
- Nephrotoxicity, ototoxicity (more commonly vestibular)
- irreversible toxicity can occur even after drug is discontinued
- one of the most common causes of drug-indcued renal failure
Tetracyclines mechanism
Competitively blocks tRNA binding to the 30S subunit , preventing the addition of a new amino acid
Reversible (bacteriostatic)
Tetracycline dosing info
- oral
- reduce bioavailability if taken w/ mineral supplements, antacids, bismuth salicylate products, dairy
Tetracycline coverage
- Broad spectrum bacteriostatic
- includes rickettsia, spirochetes, mycoplasma, chlamydia
- many common pathogens have developed resistance
Tetracycline adverse effects
- CI in pregnancy, children <8 d/t it concentrating in growing bones and teeth
- permanent tooth discoloration and hypoplasia of enamel
- nephrotoxicity rare - increased risk close to expiration date, w/ other nephrotoxic drugs
- hepatoxicity, esp in pregnancy
- photosensitivity
Macrolides exemplar
Azithromycin
Macrolides mechanism
- Affect 50S subunit
- inhibit peptidyl transferase which links amino acids in growing peptide chain
- interferes with translocation
Macrolides usage
- covers many of the bacteria that cause respiratory tract infections and CAP
- pts with penicillin allergy
- pneumonia in pregnancy
- pts taking other CYP3A4 drugs