Antibiotics Flashcards
Penicillin MOA, SE
Bind to penicilin binding proteins to prevent transpeptidation reactions involved in cross-linking, the final step in cell wall synthesis
SE
- GI
- > nausea, vom, diarrhoea
- > clostridium
- type 1 hypersensitivity
- > pruiritis, flushing, urticaria, angioedema, wheezing
- > anaphylaxis
- serum sickness
- > fever, rash, GNP, adenopathy, arthritis
- rash
- > morbilliform
- > SJS
- > toxic epidermal necrolysis
- neurologic
- > encephalopathy
- > seizures
- interstitial nephritis
- haematologic
- > direct combs positive haemolysis
- > immune mediated leukopenia and thrombocytopenia
Vancomycin
MOA
- binds to D-ala D-ala muramyl pentapeptide
- sterically hinders transglycosylation reactions involved in the elongation of peptidoglycan chains
SE
- red man syndrome
- nephrotoxic
- otoxicity
Aminoglycosides
MOA
- binds at 30S subunit of bacterial ribosome at A site
- interferes with initiation codon functions
- > misreading of code
- > incorporation of wrong amino acid
- > bacteriocidal
SE
- nephrotoxic
- otoxicity
- neurmuscular blockade
- > enhance effects of muscle relaxants
Spectrum
- no anaerobes
- mainly gram neg rods
- synergy
- > penicilin G/ampicillin = enterococci
- > amoxicillin = pseudomonas
Tetracyclines
Doxycycline
MOA
- binds to 30S subunit of bacterial ribosome at P site
- inhibits elongation of peptide chain
- > inhibits protein synthesis
SE
- nausea/vomiting/diarrhoea
- epigastric burning/ulcers
- tooth discolouration
- phototoxicity
- rash/stomatitis
- vestibular dysfunction
Precautions
- Liver disease
- > hepatotoxicity more likely
- Children
- > enamel dysplasia leading to caries with weeks of use
- Contraindicated after first trimester pregnancy
- Absorption impaired by
- > antacids
- > iron/calcium/zinc supplements
Chloramphenicol
MOA
- binds at 50S subunit
- inhibits activity of peptidyl transferase, inhibiting protein synthesis and bacteriostatic
SE
- grey baby syndrome
- bone marrow suppression
Macrolides
clarithromycin, erythromycin, azithromycin
MOA
- bind at 50S subunit
- bacteriostatic
SE
- GI distress (binds to motilin)
- irreversible deafness
- prolong QT
- candida infections
Spectrum
- gram positive cocci
- atypicals
- > mycoplasma pneumonia
- > trepanoma pallidum
- enterics
- > campylobacter
- > h pylori
Nitrofurantoin
MOA
- requires reduction by bacterial enzymes to produce ‘highly reactive electrophilic’ metabolites
- these inhibit protein synthesis by interfering with bacterial ribosomal proteins
- good against E coli and enterococcus
SE
- GI distress
- headaches
- hyperphosphataemia
- anaemia and eosinophilia
- transaminitis
Sulfonamides
MOA
- inhibit dihydropteroate synthetase
- prevents conversion of PABA and pteridine to dihydroteroic acid
- inhibits folic acid synthesis
SE
- hypersensitivity (SJS)
- haemolysis in G6PD
- phototoxicity
Trimethoprim
MOA
- inhibits dihydrofolate reductase
- inhibits conversion of dihydrofolic acid to tetrahydrofolic acid
- inhibits folic acid synthesis
SE
-bone marrow suppression
Quinelones
ciprofloxacin, moxafloxacin, novafloxacin
MOA
- inhibit topoisomerase II and IV, preventing DNA supercoiling
- bacteriocidal
SE
- dose reduction in kidney disease
- iron and calcium limit absorption
- tendonitis, tendon rupture
- phototoxicity
- CNS effects (headaches, dizziness, insomnia)
Spectrum
- broadly -> gram neg enterics and respiratory pathogens
- cipro = aerobic gram neg rods
- levo and moxi = gram positive
- moxi = anaerobes
Metronidazole
MOA
- in anaerobes, converted to free radicals by ferrodoxin
- binds to DNA, bacteriocidal
SE
- metallic taste
- GI distress
- > take just before meals
- nausea/anorexia
- dizziness
- headache
- disulfurim like effect
- > avoid alcohol up to 24hrs post treatment
Spectrum
- anaerobic gram neg
- clostridium
- h pylori
Cephalosporins
MOA: penicilin action
SE:
- GI
- > nausea, vom, diarrhoea
- > clostridium
- type 1 hypersensitivity
- > pruiritis, flushing, urticaria, angioedema, wheezing
- > anaphylaxis
- serum sickness
- > fever, rash, GNP, adenopathy, arthritis
- rash
- > morbilliform
- > SJS
- > toxic epidermal necrolysis
- neurologic
- > encephalopathy
- > seizures
- interstitial nephritis
- haematologic
- > direct combs positive haemolysis
- > immune mediated leukopenia and thrombocytopenia
Spectrum of action penicilins
narrow
-penicilin G and V
-gram positive cocci and rods (including listeria)
-some gram negative cocci (meningococcus)
very narrow
-methicilin, oxacillin
-staphlyococci
broad
-amoxicillin, ampicillin
-gram positive cocci, some gram negative rods (e coli, h influenzae)
-h pylori = amoxicilin
-listeria monocytogenes = ampicillin
extended spectrum
-ticarcillin, pipercillin
-increased activity gram negative rods (including pseudomonas)
cephalosporin spectrum of action
first gen
- cephazolin, cephalexin
- gram positive cocci, gram negative rods
- no CNS access
second gen
- cefuroxime (CNS access, lipid soluble)
- increase gram neg rods, including some anaerobes
third gen
- cephetaxime, ceftriaxone
- increased against gram neg cocci (neisseria gonorrhea)
- no action against LAME
- > listeria
- > atypicals (chlamydia, mycoplasma)
- > MRSA
- > enterocci
- enter CNS
Imipenem and meropenem
MOA
- same as penicilins
- beta lactamase resistance
SE
- GI distress
- drug fever
- cross allergy with penicilins
- seizures
Spectrum
- gram positive cocci
- gram neg rods
- anaerobes
