Antibiotics Flashcards
penecilins
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action: kills bacteria through binding of the beta-lactam ring to DD-transpeptidase, inhibiting its cross-linking activity and preventing new cell wall formation
time or concentration dependant?: Time
bacteriostatic vs bacteriocidal?: Bactericidal
spectrum of action: Gram + gram - and anerobes
tissue distribution: Serum, bile, tissues and synovial fluid
absorbtion: Rapidly absorbed SC, IM and orally
metabolism and excretion: renal with some hepatic metabolism, excreated in urine
Cephalosporins
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action: As penicillin
kills bacteria through binding of the beta-lactam ring to DD-transpeptidase, inhibiting its cross-linking activity and preventing new cell
time or concentration dependant?: Time
bacteriostatic vs bacteriocidal?: Bactericidal
spectrum of action: Broad spec of aerobes and anerobes
tissue distribution: Tissues and pleural fluid, synovial fluid and bone,
absorbtion: IV or IM, some can be administered orally
metabolism and excretion: Metabolised in liver, with renal and some hepaticexcreation
Tetracyclines
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action: inhibit the 30S ribosomal subunit, hindering the binding of the aminoacyl-tRNA to the acceptor site on the mRNA-ribosome complex, so the bacteria cannot grow or replicate
time or concentration dependant?: Concentration and time
bacteriostatic vs bacteriocidal?: Bacteriostatic
spectrum of action:
Broad spec gram + and - plus atypical bacteria
tissue distribution:
Enter all tissues but most concentrated in kidneys, liver, bile, lungs, spleen, and bone
absorbtion:
IV or oral
metabolism and excretion:
About ⅓ of dose is excreated unchanged, metabolised in kidneys and GIT, excreated in urine, faeces and aprox 10% through bile
Aminoglycosides
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
bactericidal activity in which they bind to the bacteria ribosomal 30S subunit.
time or concentration dependant?:
concentration-dependent
bacteriostatic vs bacteriocidal?:
bactericidal
spectrum of action:
Aerobic gram negatives
tissue distribution:
polar at physiologic pH
limited distribution to: extracellular fluids, with minimal penetration into most tissues. Exceptions: renal cortex of kidneys
endolymph of the inner ear. ←sites at which aminoglycosides increasingly accumulate as ionization increases.
absorbtion:
poorly absorbed orally and typically are given parenterally, either by intravenous or intramuscular injection
metabolism and excretion:
the body does not metabolise aminoglycosides
Aminoglycosides are excreted by glomerular filtration and have a serum half-life of 2 to 3 hours
Fluoroquinolones
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
target DNA gyrase and topoisomerase IV with varying efficiency in different bacteria and inhibit their control of supercoiling within the cell, resulting in impaired DNA replication (at lower concentrations) and cell death (at lethal concentrations)
time or concentration dependant?:
concentration-dependent
bacteriostatic vs bacteriocidal?:
bactericidal
spectrum of action:
Broad-spectrum antibiotics that are active against both Gram-positive and Gram-negative bacteria, including mycobacteria, and anaerobes
tissue distribution:
After oral and parenteral administratio: fluoroquinolones are widely distributed in most extracellular and intracellular fluids and are concentrated in the prostate, lungs, and bile.
absorbtion:
Oral absorption is diminished by coadministration of polyvalent cations (aluminum, magnesium, calcium, zinc, and iron preparations).
IV and orally
metabolism and excretion:
Most fluoroquinolones are metabolized in the liver and excreted in urine, reaching high levels in urine. Moxifloxacin is eliminated primarily in bile.
Sulphonamides and potentiated sulphonamides
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
potentiated sulfonamides are Protein synthesis, metabolic processes, and inhibition of growth and replication occur in organisms that cannot use preformed (eg, dietary) folate. The effect is bacteriostatic, although a bactericidal action is evident at the high concentrations that may be found in urine. Diaminopyrimidines such as trimethoprim inhibit dihydrofolate reductase, which is further into the folic acid synthesis pathway. The combination of a sulfonamide and a diaminopyrimidine results in synergistic bactericidal actions on susceptible organisms; as such, the combination is referred to as a potentiated sulfonamide.
time or concentration dependant?:
time dependent
bacteriostatic vs bacteriocidal?:
Bacteriostatic
HOWEVER-
when combined with a pyrimidine potentiator, a sequential blockade of microbial enzyme systems occurs with bactericidal consequences.
spectrum of action:
broad spectrum antimicrobial agents that inhibit the growth of gram-positive and gram-negative bacteria, Actinomycetes, Chlamydiae, and of some protozoa, such as Toxoplasma and Plasmodia. Resistance to sulfonamides has increased among many of these organisms.
tissue distribution:
Sulfonamides are weak acids and hydrophilic, leading to distribution via the extracellular fluid. The distribution pattern depends on the ionization state of the sulfonamide, the vascularity of specific tissues, the presence of specific barriers to sulfonamide diffusion, and the fraction of the administered dose bound to plasma proteins. The unbound drug fraction is freely diffusible.
Sulfonamides are bound to plasma proteins to a greater or lesser extent, and concentrations in pleural, peritoneal, synovial, and ocular fluids may be 50%–90% of that in blood. Sulfadiazine is ≥90% bound to plasma proteins. Concentrations in the kidneys exceed plasma concentrations, and those in the skin, liver, and lungs are only slightly less than the corresponding plasma concentrations. Concentrations in muscle and bone are ~50% of those in the plasma, and those in the CSF may be 20%–80% of blood concentrations, depending on the particular sulfonamide.
Low concentrations are found in adipose tissue. After parenteral administration, sulfamethazine is found in jejunal and colonic contents at about the same concentration as in blood. Passive diffusion into milk also occurs; although the concentrations achieved are usually inadequate to control infections, sulfonamide residues may be detected in milk. Trimethoprim and ormetoprim are basic and tend to accumulate in more acidic environments such as acidic urine, milk, and ruminal fluid.
Trimethoprim diffuses extensively into tissues and body fluids. Tissue concentrations are often higher than the corresponding plasma concentrations, especially in lungs, liver, and kidneys. Approximately 30%–60% of trimethoprim is bound to plasma proteins.
absorbtion:
PO, IV, IP, IM, intrauterine, or topically, depending on the specific preparation. Most are rapidly and completely absorbed from the GI tract of monogastric animals. Absorption from the ruminoreticulum is delayed, especially if ruminal stasis is present. For sulfachlorpyridazine, bioavailability is greatly decreased via feeding. Therapeutic doses of sulfonamides are usually administered PO except in acute life-threatening infections when IV infusions are used to establish adequate blood concentrations as rapidly as possible
Sulfonamides are frequently added to drinking water or feed either for therapeutic purposes or to improve feed efficiency. A few highly water-soluble preparations may be injected IM (eg, sodium sulfadimethoxine) or IP (some irritation of the peritoneum can occur). Absorption is rapid from these parenteral sites. Generally, sulfonamide solutions are too alkaline for routine parenteral use.
Trimethoprim is rapidly absorbed after administration PO (plasma concentrations peak in ~2–4 hours) except in ruminants, in which it tends to be trapped in the ruminoreticulum and appears to undergo a degree of microbial degradation.
Absorption occurs readily from parenteral injection sites; effective antibacterial concentrations are reached in < 1 hour, with peak concentrations in ~4 hours.
metabolism and excretion:
Sulfonamides are usually extensively metabolized, mainly via several oxidative pathways, acetylation, and conjugation with sulfate or glucuronic acid. Species differences are marked in this regard. The acetylated, hydroxylated, and conjugated forms have little antibacterial activity. Acetylation (poorly developed in dogs) decreases the solubility of most sulfonamides except for the sulfapyrimidine group. The hydroxylated and conjugated forms are less likely to precipitate in urine
Most sulfonamides are excreted primarily in the urine. Bile, feces, milk, tears, and sweat are excretory routes of lesser importance. Glomerular filtration, active tubular secretion, and tubular reabsorption are the main processes involved. The proportion reabsorbed is influenced by the inherent lipid solubility of individual sulfonamides and their metabolites and by urinary pH. Urinary pH, renal clearance, and the concentration and solubility of the respective sulfonamides and their metabolites determine whether solubilities are exceeded and crystals precipitate. This can be prevented by alkalinizing the urine, increasing fluid intake, reducing dose rates in renal insufficiency, and using triple-sulfonamide or sulfonamide-diaminopyrimidine combinations
Metronidazole
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
diffuses into the organism, inhibits protein synthesis by interacting with DNA, and causes a loss of helical DNA structure and strand breakage
time or concentration dependant?:
concentration-dependen
bacteriostatic vs bacteriocidal?:
bactericidal
spectrum of action:
All obligate anaerobic bacteria (it is inactive against facultative anaerobic and aerobic bacteria)
Certain protozoan parasites (eg, Trichomonas vaginalis, Entamoeba histolytica, Giardia intestinalis [lamblia])
tissue distribution:
It is distributed widely in body fluids and penetrates into cerebrospinal fluid, resulting in high concentrations
absorbtion:
Oral metronidazole is absorbed well. It is usually given IV only if patients cannot be treated orally
metabolism and excretion:
Metronidazole is metabolized presumably in the liver and excreted mainly in urine, but elimination is not decreased in patients with renal insufficiency. However, because metronidazole metabolites may accumulate in patients with end-stage renal disease, these patients should be monitored for metronidazole-associated adverse effects
Macrolides
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
nterfere with protein synthesis
time or concentration dependant?:
time
bacteriostatic vs bacteriocidal?:
bacteriostati
spectrum of action:
gram +ve bacteria
tissue distribution:
wide tissue distribution, tend to concentrate in spleen, liver, kidneys and lungs. Do not enter eye or CNS
absorbtion:
absorbed easily from GIT
also subcut or IM
metabolism and excretion:
Excreted in bile, also goes into milk
Lincosamides
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
suppress protein synthesis
time or concentration dependant?:
time
bacteriostatic vs bacteriocidal?:
bacteriostatic
spectrum of action:
broad spectrum against anaerobic bacteria
tissue distribution:
Lipid soluble - wide distribution including bone, poor CNS infiltration, can diffuse across placenta in some species
absorbtion:
absorbed from GIT
Also good absorption IM
metabolism and excretion:
metabolised in liver, excreted in bile and urine and milk
Phenicols
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
inhibits protein synthesis
time or concentration dependant?:
time
bacteriostatic vs bacteriocidal?:
bacteriostatic but can be bacteriocidal in high concentrations
spectrum of action:
most things. Especially anaerobes - MRSA, salmonella, pasteurella, mycoplasma, brucella
tissue distribution:
most tissues including the brain, highest concentrations in kidneys, liver and bile, reaches CNS and inside eye. Crosses placenta
absorbtion:
GIT, IM or IV
metabolism and excretion:
metabolised in liver, renal excretion
Polymyxin B
mechanism of action
time or concentration dependant?
bacteriostatic vs bacteriocidal?
spectrum of action
tissue distribution
absorbtion
metabolism and excretion
mechanism of action:
interact with cell membrane phospholipids to disrupt their permeability
time or concentration dependant?:
concentration
bacteriostatic vs bacteriocidal?:
bacteriocidal
spectrum of action:
more effective against gram negative, narrow spectrum
tissue distribution:
topical application of enteral for GI treatment only
absorbtion:
enteral for GI or topical
metabolism and excretion:
renal excretion - nephrotoxic
