Antimicrobial Agents: Antibiotics Exam 1 Flashcards
Bacteriostatic
prevents bacteria from continuing to grow/multiply
Bactericidal
kills bacteria
Can bacteriostatic or bactericidal be used longer?
bacteriostatic
Pharmacokinetics
movement of a drug from administration site to the place of its activity, distribution in the body, metabolism/bioavailability, and elimination/excretion from the body
What organ metabolizes drugs?
liver
What happens if bioavailability is low?
the drug cannot be metabolized as well by the liver
Pharmacodynamics
the effect of the drug in the body
Factors affecting kinetics:
-release from dosage form
-absorption from the site of administration into the bloodstream
-distribution to various parts of the body, including site of action
-rate of elimination from the body via metabolism or excretion of unchanged drug (how long will it circulate in the body)
Blood brain barrier purpose:
prevents drugs from reaching the brain
Time-dependent drugs
bactericidal activity continues as long as the plasma concentration is greater than the minimum bactericidal concentration
How often do time-dependent drugs need to be administered?
-several times a day
-drugs should be maintained above the MIC
Concentration-dependent drugs
the rate and extent of killing increases as the peak drug concentration increases
-want to stay just above the line
What drugs exhibit a Post-Antibiotic Effect?
concentration-dependent drugs
Post-antibiotic effect
persistent suppression of bacterial growth after dose
-long post-antibiotic effect = longer dosing intervals
How many antibiotics can we use at a time (generally speaking?)
1
Gram (+) bacteria examples
-staph
-strep
Gram (-) bacteria examples
-E. Coli
-salmonella
-pseudomonas
Which gram type is more difficult to kill?
gram (-)
-requires non-simple and more toxic antibiotics
4 Classes of Antibiotics
- cell wall synthesis inhibitors
- protein synthesis inhibitors
- folic acid synthesis inhibitors
- DNA synthesis inhibitors
Which class of antibiotic is the oldest?
cell wall synthesis inhibitors
Cell Wall Synthesis Inhibitors
-beta-lactam antibiotics
-cephalosporins
-penicillins
-cannot harm our cells because we do not have cell walls
Protein synthesis inhibitors
-tetracyclines
-macrolides
-act on ribosomes (different from the ribosomes in our cells)
Folic Acid Synthesis inhibitors
-sulfonamides (SMZs, TMZs)
-trimethoprim
-work on the folic acid (we also need folic acid in our cells so these can be toxic to us)
DNA synthesis inhibitors
quinolones
How does bacteria spread?
-some move
-most spread by multiplying and through blood circulation
Principles of antibiotic therapy:
-harm the parasite, not the host
-mechanism of action: processes unique to bacteria
-processes common to bacteria and host = more affinity for bacteria
Types of bacteria
-gram +
-gram -
-aerobic
-anaerobic
What type of bacteria is penicillin great for?
gram +
What is the oldest antibiotic?
penicillin
How can penicillin be unstable?
-in acidic pH - pus is acidic and penicillin cannot survive in the stomach so it cannot be taken orally
-susceptible to destruction by beta-lactamase (in some bacteria)
Beta-lactamase
-found in some bacteria
-can lead to super infection = bacteria feeds on penicillin and multiplies
-destroys penicillin
Types of penicillin
-penicillin G
-penicillin V
-procaine penicillin
-benzathine penicillin
How is penicillin adminstered?
-in hospitals: IV
-most common outside of hospitals: IM (hurts a lot)
What are common diseases penicillin is used to treat?
-strangles
-strep
-meningococcus
-anthrax
-clostridium
Side effects of penicillin
-non-toxic unless host is allergic
-anaphylactic shock
-diarrhea (super infection)
-resistance
-yeast infection
Semi-synthetic penicillins
-ampicillin
-amoxicillin
-methicillin (MRSA)
Cephalosporins
-similar to penicillins: chemically, mechanism of action, and toxicity
-more stable to bacterial beta-lactamase
How are cephalosporins divided?
into 1st, 2nd, 3rd, and 4th generations
1 = gram +
2 = gram + and -
3 = gram + and -
4 = gram -
How can cephalosporins be given?
PO, IM, IV
What two beta-lactamase inhibitors work well together?
amoxicillin and clavulonic acid
Vancomycin
-beta-lactam
-can only be given IV (in hospital setting)
-can be toxic to kidneys and ears
Bacitracin
-excellent in killing bacteria
-VERY toxic
-reduced toxicity by putting it in an ointment
Triple antibiotic ointment is made up of what?
- bacitracin
- neomycin
- polymyxin
Tetracyclines treat what types of bacteria?
Broad spectrum
-gram +
-gram -
-rickettsia
-anaerobic
-protozoa
Tetracyclines
-protein synthesis inhibitor
-accumulates inside the bacterial cell, binds to ribosomes, impedes formation of new protein
-bacteria will slowly die (starve the bacteria)
What does tetracycline bind to/join with?
chelate calcium and other divalent cations (Mg2+)
How are tetracyclines administered?
PO
IV - diluted and administered slowly (bc calcium is needed for muscle contraction)
Who should avoid tetracyclines?
young and pregnant individuals
-bc it chelates with Ca which is needed for bone growth
What is the one time tetracycline would be used in foals?
in foals with contracted tendons
-it removes the Ca that is contracting the tendons to get them to relax
How should you take tetracyclines orally?
not with any Ca containing product (milk) because it nulls the drug
Oxytetracycline
LA 200!
-what is given to foals with contracted tendons
What tetracycline does not chelate Ca as much as oxytetracycline?
Doxycycline
-given orally
-must wear gloves (iron gets absorbed)
-can lead to anemia after long-term use
What horses do not use Macrolides?
any horses over the age of 1
What happens if adults take macrolides?
severe diarrhea
Most common macrolide
erthromycin
Two examples of macrolides
-clarithromycin
-azythromycin (2-pac)
What is used with macrolides to treat Rhodococcus equi pneumonia in foals?
rifampin (if rhoda is resistant-use doxycycline)
Side effects of macrolides
-diarrhea
-light sensitivity
-fever
Aminiglycosides
very good in killing bacteria but very toxic, destroys kidneys and has more severe side effects
-used against enteric bacteria
-only used in ointments (except gentamicin)
Types of aminoglycosides (protein synthesis inhibitors)
-streptomycin
-neomycin (eye ointment)
-gentamicin
-amikacin (join injections to prevent joint infections)
-trobramycin (eye ointment)
What is essential for nucleic acid synthesis?
folic acid (some microbes need extracellular PABA to form folic acid)
What are sulfonamides structurally similar to?
PABA
Sulfonamides
-folic acid synthesis inhibitor
-reversibly block folic acid synthesis (PABAs pick up sulfas instead of creating folic acid)
-bacteriostatic
-not very useful by itself anymore
Trimethoprim
-folic acid synthesis inhibitor
-used generally in conjunction with SMZs
-synergism
SMZs and TMPs
Sulfonamides + what makes them bacteriocidal?
trimethoprim
Fluoroquinolones: Floxacins
-newest antibiotic
-DNA synthesis inhibitor
-broad spectrum
-MRSA
Side effects of Floxacins
tendon laxity (usually in young animals)
Floxacins are useful against what bacteria?
all but especially E.Coli when it becomes resistant to SMZ-TMP
What is usually the last resort drug type in horses?
Flaxacins
