Antibiotics

Antibiotics
Chapter 37

Antibiotics
I Definition:
A. medications used to treat bacterial infections
B. Ideally, before beginning antibiotic therapy, the suspected areas of infection should be cultured to identify the causative organism and potential antibiotic susceptibilities

II Classes
A. Sulfonamides
B. Penicillins
C. Cephalosporins
D. Tetracyclines
E. Macrolides
F. Aminoglycosides
G. Quinolones

III Antibiotic Therapy
A. Empiric therapy: treatment of an infection before specific culture information has been reported or obtained
B. Prophylactic therapy: treatment with antibiotics to prevent an infection, as in intraabdominal surgery.
C. Therapeutic response:
Decrease in specific signs and symptoms of infection are noted (fever, elevated WBC, redness, inflammation, drainage, pain)
1. Streamline therapy: after results from C&S come back, change to the appropriate antibiotic. (narrow down) Broad spectrum causes resistance.
D. Subtherapeutic response:
Signs and symptoms of infection do not improve.
1. Superinfection: occurs when antibiotics reduce or completely eliminate the normal bacterial flora
2. antibiotic resistance:
3. host factors: age, allergy history, kidney and liver function, pregnancy, genetic characteristics, site of infection, host defenses
4. genetic host factors
a. G6PD deficiency
b. slow acetylator metabolic status
5. allergic reactions: especially to pcn (any “illins”) and sulfa drugs
IV Mechanism of Action
A. Interference with cell wall synthesis
B. Interference with protein synthesis
C. Interference with DNA replication
D. Acting as a metabolite to disrupt critical metabolic reactions inside the bacterial cell
E. Actions of Antibiotics
1. bactericidal: kill bacteria
2. bacteriostatic: inhibit growth of susceptible bacteria, rather than killing them immediately; will eventually lead to bacterial death





Sulfonamides
I Definition: one of the first groups of antibiotics.
II Drugs:
A. sulfadiazine
B. sulfamethoxazole: primary one used today in combination w/another antib.
C. sulfisoxazole
III Mechanism of Action
A. Bacteriostatic action
B. prevent synthesis of folic acid required for synthesis of purines and nucleic acid
C. Do not affect human cells or certain bacteria, they can use preformed folic acid
IV Indications
A. Treatment of UTI’s caused by susceptible strains of:
1. Enterobacter
2. Escherichia coli
3. Klebsiella
4. Proteus mirabilis
5. Proteus vulgaris
6. Staphylococcus aureus
B. Nocardiosis
C. Pneumocystis carinii pneumonia (PCP) co-trimoxazole This is a protozoa, not a bacteria. It is best treated by sulfonamides. Bactrim. Use high doses.
D. Upper respiratory tract infections
E. other uses
V Sulfanomides: Combination products
A. trimethoprim/sulfamethoxazole (Bactrm, Septra)
1. used to treat UTI’s, PCP, otitis media, others.
2. drink alot of water.
3. Don’t really use sulfa products alone anymore; we combine them so they work better.
VI Side effects:
Stevens-Johnson syndrome, epidermal necrolysis




Beta-Lactam Antibiotics

Penicillins
I Types
A. Natural penicillins
1. penicillin G
2. penicillin V potassium
B. Penicillinase-resistant penicillins (after natural became resistant we used these, didn’t last long)
1. cloxacillin
2. dicloxacillin
4. nafcillin
5. oxacillin
C. aminopenicillins (became resistant)
1. amoxicillin
2. ampicillin
3. bacampicillin
D. extended-spectrum penicillins
1. piperacillin
2. ticarcillin
3. carbenicillin
E. Can take monobactam if allergic to pcn, not cephalosporin or carbapenems.
II Facts
A. first introduced in the 1940’s, discovered by Fleming
B. bacteriacidal: inhibit cell wall synthesis
C. kill a wide variety of bacteria
D. also called beta lactams
E. bacteria produce enzymes called beta-lactamases which are capable of destroying penicillins. As a result, the medication is not effective. This is a method of resistance.
F. Chemicals have been developed to inhibit these enzymes. They bind with beta-lactamase and prevent the enzyme from breaking down the pcn.
1. clavulanic acid ( + ticarcillin = Timentin)
2. tazobactam (+ piperacillin = Zosyn)
3. sulbactam (+ampicillin = Unasyn)
4. clavulanic acid (+amoxicillin = Augmentin)
III Mechanism of Action
A. enter the bacteria via the cell wall
B. inside the cell they bind to penicillin binding protein
C. once bound, normal cell wall synthesis is disrupted
D. Result: bacteria cells die from lysis

IV Indications
A. prevention and treatment of infections caused by susceptible bacteria, such as:
1. gram + bacteria
2. Streptococcus, Enterococcus, Staphylococcus
V Adverse Effects
A. allergic reactions occur in 0.7% to 8% of cases
1. urticaria
2. pruritus
3. angioedema
B. 10% of allergic reactions are life threatening
1. 10% of these are fatal (All can be life threatening, all can be fatal)
VI Side effects
A. common: n/v, diarr, abd pain...others are less common

Beta-Lactam Antibiotics
Cephalospporins
I Types
A. 1st generation (good gram + coverage. Poor gram – coverage.)
1. cephalexin (Keflex) PO
2. cefazolin (Ancef and Kefzol) IV only
3. used for surgical prophylaxis, URI’s, otitis media
B. 2nd generation
1. good gram + coverage, better gram – than 1st generation
2. cefoxitin (Mefoxin) IV and IM
a. used prophylactically for abd or colorectal surgeries
b. kills anaerobes
3. cefuroxime (Kefurox and Ceftin) PO
a. surgical prophylaxis
b. does not kill anaerobes
C. 3rd generation
1. most potent group against gram negative, less active against gram +
2. ceftriaxone (Rocephin)
a. IV and IM
b. long ½ life
c. once a day dosing
d. easily passes meninges and diffused into CDF to treat CNS infections. Great for meningitis and shingles
e. NOT RENALLY ELIMINATED billiary/liver so can cause diarrhea.
f. covers all/most gram – and strepto pneumon, gonorrhea. (does not cover pseudomonas)
3. ceftazidime (ceptaz, fortaz, taxidime, tazicef)
a. IV and IM
b. excellent gram – coverage
c. used for difficult to treat organisms such as Pseudomonas
4. cefixime (Suprax) ONLY ORAL 3RD GENERATION AGENT
a. best of available oral cephalosporins against gram –
b. tablet and suspension


D. 4th generation
1. cefepime (Maxipime)
2. newest
3. broader spectrum esp against gram +
II Facts
A. semisynthetic derivatives from a fungus
B. structurally and pharmacologically related to pcn
C. Bacteriacidal
D. broad spectrum
E. divided into groups according to their antimicrobial activity
III Side effects
A. similar to pcn

Beta-Lactam Antibiotics
Carbapenems
I Facts
A. very broad spectrum antibacterial action
B. reserved for complicated body cavity and connective tissue infections
C. may cause drug induced seizure activity (imipenem-cilastatin...Primaxin)
D. used for treatment of bone, joint, skin, and soft tissue infections; many other uses
E. if allergic to pcn, allergic to this also

Beta-Lactam Antibiotics
Monobactams
I Facts
A. aztreonam (Azactam)
B. synthetic
C. primarily active against aerobic gram – bacteria (E. coli, Klebsiella, Pseudomonas)
D. If you are allergic to pcn you CAN take this

Macrolides
I Types
A. erythromycin (Emycin, EES)
B. azithromycin (Zithromax)
C. clarithromycin (Biaxin)
II Mechanism of Action
A. prevent protein synthesis within bacterial cells
B. bacteria will eventually die
C. bacteriastatic
D. all liver metabolized
III Indications (treat atypical organisms)
A. strep infections
B. mild to moderate URI
C. haemophilus influenzae

D. spirochetal infections
1. syphillis
2. lyme disease
E. gonorrhea, chlamydia, mycoplasma
IV Side effects
A. GI effects primarily with erythromycin
B. newer agents fewer side effects, better action
1. azithromycin
2. clarithromycin: bad metallid taste in mouth

Tetracyclines
I types
A. tetracyline: used for acne. Discolors teeth, crosses placenta & breastmilk
B. demeclocycline is also used to treat SIADH And pleural and pericardial effusions (symptoms of inappropriate ADH)
II Facts
A. natural and synthetic
B. obtained from cultures of streptomyces
C. bacteriostatic
D. inhibit protein synthesis
E. stop many essential function of the bacteria
F. Dairy products, antacids, and iron salts reduce absorption of tetras Has a strong affinity for calcium.
1. discoloration of permanent teeth and tooth enamel in fetuses and children
2. may retard fetal skeletal develop if taken during pregnancy
III Indications
A. wide spectrum
1. gram -, gram +, protozoa, mycoplasma, rickettsia, chlamydia, syphilis, lyme disease
IV Side effects
A. discoloration of permanent teeth and tooth enamel in fetuses and children
B. may retard fetal skeletal develop if taken during pregnancy
C. Alteration in intestinal flora may result in:
1. superinfection (overgrowth)
2. diarrhea
3. pseudomembranous colitis/bloody diarrhea
D. may also cause:
1. vaginal moniliasis
2. gastric upset
3. enterocolitis
4. maculopapular rash





Aminoglycosides
I Types (systemic)
A. gentamicin (Garamycin)
B. tobramycin
C. amikacin (Amikin)
II Facts
A. natural and semisynthetic
B. produced from streptomyces
C. poor oral absorption NO PO FORMS
D. very potent antibiotics with serious toxicities
E. Bacteriacidal
F. kills mostly gram –
G. Narrow therapeutic window. We must pull levels on this. Serious toxicities.
H. TOXIC TO KIDNEYS AND EARS
III Indications
A. kill gram -. Pseudomonas, e. coli, proteus, klebsiella, serratia
B. often used in combination with others for synergistic effect
C. narrow therapeutic window medications
D. All poorly absorbed through GI, the exception is neomycin.
1. given orally to decontaminate the gi tract before surgery
2. also used as an enema for this purpose
IV Side effects
A. cause serious toxicities
1. nephrotoxicity
2. ototoxicity: auditory impairment and vestibular 8th cranial nerve
B. must monitor drug levels to prevent toxicities
C. headache, paresthesia, dizziness, vertigo, skin rash, fever, superinfection

Quinolones
I Types
A. ciprofloxacin (cipro)
B. levofloxacin (levaquin)
II Facts
A. excellent oral absorption, as good as an IV
B. absorption reduced by antacids
C. first oral antibiotics effective against gram- bacteria (some +)
D. bactericidal
III Indications
A. Anthrax among others
IV Side effects
A. headache, dizziness, depression
B. n/v/d/constipation/
C. rash, photosensitvity
D. fever chills, blurred vision, tinnitus
Other
I Vancomycin (stands alone)
A. treatment of choice for MRSA and other gram +
B. monitor blood levels
C. ototoxicity and nephrotoxicity
D. should be infused over 90 minutes
E. Redman’s syndrome

Nursing implications
It is essential to obtain cultures from appropriate sites before beginning therapy.
Take exactly as prescribed and for the length of time prescribed.
Assess for superinfection.
Check the name of med carefully because of look/sound alikes
Take w/ 6-8 oz water
Most common side effects: n/v/d
Sulfonamides:
Take w/2000 ml fluid/day
Photosensitivity
Reduce contraceptives
Take w/food or milk to reduce upset
Penicillins
Allergic rxn for 30 min
Decreased w/caffeine, citrus, cola, tomato juice
Cephalosporins
Give w/food
No alcohol
Tetracyclines
Avoid dairy b/c of chelation
Photosensitivity
Aminoglycides
Nephrotoxicity....peak and trough levels
Ototoxicity...dizziness, tinnitus, hearing loss

Test Questions:

Penicillins can cause seizures if dosed too high. True.
(renally eliminated, if bad renal function...retain more drug.)

What was added to penicillins to prevent beta-lactamases from working?
Clavulanic acid, tazobactam, sulbactam.

Bacteriastatic
Macrolides
Tetracycline
sulfonamides

Bactericidal
Aminoglycosides
Quinolones
Pencillin
Cephalosporins
Carbapenems
Monobactams
vancomycin