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Mel's Pharmacology Lecture Nov 06


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Name 6 Abuses of Antibiotics
1. for viral infections
2. fever of unknown origin (vaild in immune compromised patients)
3. too small or too large of a dose
4. administration before culture and sensitivity analysis
5. used instead of proper cleansing
6. not finishing prescribed amount / sharing medications
Describe selective toxicity and 3 ways it is attained in antimicrobial therapy
Selective toxicity is the ability of a drug to injure invading microbes without injuring cells of the host.
Antibiotic therapies achieve this by:
1) targeting bacterial cell wall
2) inhibiting enzyme unique to the bacteria
3) disrupting the protein synthesis of bacterial cells
Describe narrow spectrum antibiotics versus broad spectrum antibiotics
Narrow spectrum antibiotics are active against only a few microorganisms, whereas broad-spectrum antibiotics are active against a wide array of microbes
How can we (in the hospital) delay resistance and the emergence of antibiotic resistance (in 4 basic ways)
1. Prevent infection (e.g. decrease invasive procedures, tubes, lines)
2. diagnosing and treating infection effectively (target microorganism / infection)
3. Using antimicrobial drugs wisely (vancomycin "big guns" as last resort, stop drugs when infection is gone)
4. prevent patient-patient transmission--break the chain of resistant infections
What is the difference between bacteriostatic drugs and bactericidal drugs
Bacteriostatic drugs suppress growth, bactericidal drugs kill bacteria
Resistance: What is it? How are resistant bacteria spreading? Are antibiotics causing the creation of resistant bacteria?
* Antibiotic resistant bacteria respond slower or not at all to antibiotic therapies.
* They acquire resistant properties through "conjugation", where the bacteria's DNA coding for drug resistance is passed from one bacteria to another
* Antibiotics do not cause the genetic changes, but promote the emergence of drug-resistant organisms by creating selection pressures that favor them.
Name 4 appropriate prophylactic antimicrobial treatments
1. certain surgeries
2. neutropenia
3. recurrent uti's
4. patients at risk for bacterial endocarditis
What is cross resistance?
Broad spectrum vs. narrow spectrum
* Cross resistance is when bacteria become resistant to ANOTHER antibiotic with the same compounds.
* More risk of resistance with use of broad spectrum antibiotics versus narrow spectrum bacteria
What is the MIC of an antibiotic?
The MIC (minimum inhibitory concentration) of an antibiotic is the lowest concentration of drug needed to completely suppress bacterial growth
Describe 5 General Adverse Reactions to Antibiotics
1) Allergy/Hypersensitivity
2) GI upset (take w meals/ may have decreased absorption)
3) Suprainfection: while you're taking care of one infection (killing bacteria in your body, including good bacteria) a second one emerges (i.e., yeast infections)
4) Organ toxicity--liver (fatty infiltrate, jaundice) usually on higher doses
4 Types of Penicillins (we are on the 3rd - 4th generation)
1. Penicillin V: similar to G, narrow spectrum, more stable in stomach acid, preferred for oral
2. Penicillin G: 1st penicillin, narrow spectrum
3. Ampicillin: broad spectrum, IV or oral
4. Amoxicillin: broad spectrum, oral, very similar to Ampicillin, but more acid resistant--better choice for oral
*Mechanism of Action
*ACTION: Penicillins weaken the bacterial cell wall, causing lysis and death
*USES: Strep, Syphilis, Meningitis, Anthrax
*Forms: po (empty stomach), IV, IM
*Elimination: Kidneys
Describe 2 types of bacterial resistance to penicillins
* gram negative bacteria are resistant to penicillins that cannot penetrate the gram negative cell envelope
* some bacteria resist penicillins by producing enzymes that inactivate penicillins
* Mechanism of Action
* Uses
* Forms
* Elimination
* Cephalosporins are beta-lactam antibiotics that weaken the bacterial cell wall--they are similar in structure and action to penicillin
* UTI, mastitis
*FORMS: po, IV, IM
* Elimination: Kidneys
As you progress from 1st generation - 4th generation agents, there is 1) increasing activity against gram - bacteria, 2) increasing resistance to destruction by beta-lactamases, 3) increasing ability to reach the cerebral spinal fluid
CEPHALOSPORINS: Allergic reactions/sensitivities
Cephalexin (Keflex)
* Classification
* Uses
* Form
* Allergic Warnings
* Cephalosporin (broad spectrum)
* UTI, RTI, Septicemia, Otis Media, Mastitis
* p.o. Give with food/milk
* Don't give if severe penicillin
*mechanism of action
*Broad spectrum
*Inhibits bacterial protein synthesis
*Bacteriostatic (suppress growth and replication)--second line agents used primarily for infections resistant to first line agents
*3 side effects
*nursing implications
*Uses: chlamydia, lyme, anthrax
*Forms: po, iv, im, topical
*Elimination: kidneys, liver
*Side effects: photosensitivity, discolored teeth, GI upset
*nursing implications: no milk, iron, antacids (absorption will be effected), monitor kidney/liver labs for toxicity
AMINOGLYCOCIDES (i.e. gentamicin)
*mechanism of action
*Narrow spectrum, used primarily against aerobic gram - bacilli
*Disrupts protein synthesis resulting in rapid bacterial death (bactericidal)
*side effects
uses: mrsa
forms: im, iv
elimination: kidneys (can be nephrotoxic)
*thrombophlebitis (very toxic medication--watch iv site very carefully)--some hospitals you can only run through a central line

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