Nursing 3703 Pharmacology
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Transcript Nursing 3703 Pharmacology
Nursing 3703
Pharmacology
Antimicrobials
By Linda Self
Microorganisms and Infections
Microbes attach to host receptors
Attracted to a specific body tissue,
invade and multiply
Most survive in more than one type of
environment
Symptoms are result of immune
response
Age-Related ConsiderationsChildren
Penicillins and Cephalosporins
generally safe
Fewer clinical trials on children
Erythromycin, Zithromax
(azithromycin) and Biaxin
(clarithromycin) considered safe
Antimicrobials and Children
Aminoglycosides can cause ototoxicity
and nephrotoxicity.
Tetracyclines are contraindicated in
children younger than 8 years old,
effects on teeth
Cleocin (clindamycin) admin. requires
liver and kidney monitoring in
neonates and infants
Antimicrobials and Children
Fluoroquinolones contraindicated in
children under 18 yo. May have
effects on weight bearing joints.
Bactrim (trimethoprimsulfamethoxazole) no longer 1st line
due to resistance
Antimicrobials and Older Adults
Penicillins are generally safe, IV
admin. can cause hyperkalemia
Cephalosporins are considered sage
but can affect or worsen renal failure
Macrolides are generally safe
Aminoglycosides are contraindicated
in severe renal impairment
Antimicrobials and Older Adults
Aminoglycosides can also cause
ototoxicity
Cleocin (clindamycin)-diarrhea, colitis
Bactrim (trimethoprimsulfamethoxazole) may be associated
with impaired liver or kidney function
Antimicrobials and Older Adults
Tetracyclines (except doxycycline)
and Macrodantin (nitrofurantoin) are
contraindicated in impaired renal
function
In General
With most oral antibiotics, liberal fluid
intake is recommended
Always be aware of pregnancy
category before administering
medication
Bacteria
Aerobic
Anaerobic
Gram’s Stain-microscopic appearance
and color
Pathogenic
Normal flora
Lab ID of Pathogens
Culture and sensitivity
Serology-measures antibody levels
Polymerase Chain Reaction (PCR)
detects the specific DNA for a specific
organism
Common Human Pathogens
Viruses
Gram+ enterococci, streptococci and
staphylococci
Gram- organisms: E.coli, Bacteroides,
Klebsiella, Proteus, Pseudomonas
Opportunistic
Community-acquired vs. nosocomial
Antibiotic-Resistant Microorganisms
Occurs when:
Clinical condition of host is impaired
Normal flora have been suppressed
w/interrupted or inadequate tx
Type of bacteria
Widespread use of broad spectrum
abx
Environmental setting of host
Mechanisms of Resistance
By:
Generating enzymes that inactivate
the antibiotic (beta lactamase)
Changing structure of target site
(beta lactams and aminoglycosides)
Preventing cellular accumulation of
abx by altering outer membrane
proteins or using efflux pumps
Mechanisms of Resistance cont.
Changing the metabolic pathway that
is being blocked
Overproducing the target enzyme to
overpower the effects of antibiotics
Gram negatives possess an outer
membrane and cytoplasmic
membrane preventing passage of abx
through porins
Mechanisms of Resistance cont.
Mycoplasma lacks a cell wall makingit
impervious to penicillins
Sulfonamides have no impact on
bacteria that obtain their folate from
environment
Characteristics of Anti-Infectives
Includes antibacterials, antivirals and
antifungals
Antibacterials (antibiotics) refer to
drugs which treat bacterial infections
Narrow spectrum
Broad spectrum
Bactericidal (kills) vs. Bacteriostatic
(inhibits)
Host Defense Mechanisms
Breaks in skin and mucous membranes
Impaired blood supply
Neutropenia
Malnutrition
Poor personal hygiene
Suppression of normal flora
Diabetes, advanced age or
immunosuppression
Mechanisms of Action
Inhibition of bacterial cell wall
synthesis or activation of enzymes
that disrupt cell walls (PCNs,
Cephalosporins, Vancomycin_
Inhibition of protein synthesis (EES,
tetracyclines, clindamycin,
aminoglycosides)
Mechanisms of Action cont.
Disruption of microbial cell
membranes (anti-fungals)
Inhibition of organism reproduction
by interfering w/nucleic acid synthesis
(fluoroquinolones, HIV antiretrovirals)
Inhibition of cell metabolism and
growth (sulfonamides)
Prophylactic Therapy or Empiric
Therapy
STD exposure
Recurrent UTIs
TB
Perioperative infections in high risk
patients or high risk surgeries
Bacterial endocarditis—w/cardiac
valvular disease undergoing dental,
surgical or other invasive procedures
Drug Selection
Best if based on culture and
sensitivity—”match the drug to the
bug”
MIC—minimum inhibitory
concentration—lowest concentration
of a drug that prevents visible growth
of microorganisms
Drug Selection cont.
Knowledge of organisms likely to
infect particular body tissues
Other Selection Considerations
Drug’s ability to penetrate infected
tissues (prostate, sinuses)
Drug’s toxicity and the risk-to-benefit
ratio
Drug costs
Antibiotic Combination Therapy
Used when infection is caused by
multiple microorganisms
Nosocomial infections
Serious infections in which a
combination is synergistic
(aminoglycoside and
antipseudomonal PCN)
Antibiotic Combination Therapy
cont.
Likely emergence of drug resistant
organisms
In those who are immunosuppressed
Beta Lactams
Contain a beta-lactam ring that is
part of their chemical structure
An intact beta-lactam ring is essential
for antibacterial activity
Include: Penicillins, Cephalosporins,
Carbapenems and Monobactams
Beta Lactam Mechanism of Action
Inhibit synthesis of bacterial cell walls
by binding to proteins in bacterial cell
membranes
Binding produces a defective cell wall
that allows intracellular contents to
leak out
Most effective when bacterial cells are
dividing
Penicillins
Derived from a fungus
Prototype is Penicillin G
Widely distributed except in CSF
(except if inflammation is present)
and in intraocular fluid
Most serious complication is
hypersensitivity. Can cause seizures
and nephropathy.
Indications for Penicillins
More effective in treating gram+ infections
Used to treat infections of the skin, GU, GI,
respiratory tract and soft tissues
Selection depends on the organism and
severity of the infection—anti-staph vs.
anti-pseudomonal
Combinations for beta lactamase inhibition
(Augmentin)
Examples of Penicillins
Penicillins G and V (parenteral);
dicloxacillin (antistaph);
Ampicillins—Principen, Amoxil
Antipseudomonals—Geocillin
(carbenicillin), Ticar (ticaracillin),
Pipracil (piperacillin)
Combinations for beta lactamase—
Unasyn (ampicillin/sulbactam), Zosyn
(piperacillin/taxobactam)
Examples
Antistaphylococcal—dicloxacillin,
nafcillin
Anti-pseudomonals—carbenicillin,
ticaracillin
Beta lactamase inhibition
combinations: Unasyn
(ampicillin/sulbactam), Augmentin
(amoxicillin/clavulate), Timentin
(ticaricillin/clavulanate)
Cephalosporins
Also derived from a fungus
Broad spectrum with activity against
both gram positive and gram negative
bacteria
Less active against gram positives
than penicillins
Do not penetrate CSF well
w/exception of Ceftin (cefuroxime)
and 3rd generation agents
Cephalosporins
Progressively more effective against
gram negative pathogens as progress
generationally
indications-surgical prophy, tx
infections of the respiratory tract,
skin, bone and joints, urinary tract,
brain and spinal cord and in
septicemia
Cephalosporins
Contraindicated in anaphylaxis to a
penicillin
May develop a delayed reaction
Examples
Oral—Keflex (cephalexin); Ceclor
(cefaclor), Lorabid (lorcarbef);
Omnicef (cefdinir)
Parenteral—Ancef (kefzol); Mefoxin
(cefoxitin); Claforan (cefotaxime),
Fortaz (ceftazidime), Rocephin
(ceftriaxone); Maxipime (cefepime)
Carbapenems
Broad spectrum, bactericidal, betalactam anti-microbials. Inhibit
synthesis of cell walls.
All are parenteral
Indicated for organisms resistant to
other drugs
Examples: Merrem (meropenem) and
Primaxin (imipenem-cilastatin)
Monobactams
Azactam (aztreonam) is active
against gram-negative bacteria and
to many resistant strains
Similar to aminoglycosides but no
kidney damage nor hearing loss
Stable in presence of beta lactamase
Preserves normal gram positive and
anaerobic flora
Indications for Monobactams
Infections of the:
Urinary tract
Lower respiratory tract
Skin and skin structures
Intra-abdominal and gynecologic
infections
Septicemia
FYI
Penicillins may be given with
Probenecid or aminoglycosides for
serious infections
PCN can cause nephropathies
Ticaracillin has been linked to
hypernatremia
PCN G can cause hyperkalemia
Caution w/Augmentin in hepatic
impairment
FYI
Need to adjust dosages of all beta
lactams in the presence of renal
impairment whether PCN,
cephalosporins, carbapenems and
monobactams
Aminoglycosides
Bactericidal agents to treat gram negative
organisms such as: Proteus, Klebsiella,
Enterobacter, Serratia, Escherichia coli, and
Pseudomonas
Poorly absorbed fro the GI tract so cause
local effects
Accumulate in kidneys and ears
Poorly distributed to CNS, respiratory tract
and intraocular fluids
Oral forms excreted in feces, injectables by
kidneys
Aminoglycosides cont.
Mechanism of action by penetrating
cell walls of susceptible bacteria and
bind to 30S ribosomes. Bottom line—
prevent protein synthesis and
replication.
Indicated for serious gram negative
organisms
Most often affect the respiratory, GU,
skin, wound, bowel and bloodstream
Aminoglycosides cont.
Penicillin facilitates entry of
aminoglycosdie through the bacterial
cell wall
Streptomycin is useful in tuberculosis
Synergism when used with
vancomycin, ampicillin or penicillin G
in tx of enterococcal infections
Used to suppress intestinal flora in
those with hepatic failure
Aminoglycosides cont.
Contraindicated in infections for which
less toxic drugs are effective
These drugs are nephrotoxic and
ototoxic
Must use cautiously in Myasthenia
Gravis or neuromuscular disorders
because muscle weakness may be
increased
Aminoglycosides cont.
Choice depends on local susceptibility
patterns
Gentamycin generally chosen first,
then Tobramycin or Amikacin
Dosing must be carefully regulated
because therapeutic doses are close
to toxic doses
Aminoglycosides—Management
Considerations
Initial loading dose based on ideal
weight
Are not distributed in body fat
Maintenance doses are based on
serum drug concentrations. Peak
levels should be assessed 30-60
minutes after administration.
Aminoglycoside—Management
Considerations cont.
Measurement of peak and trough
levels helps to maintain therapeutic
serum levels w/o excessive toxicity
With impaired renal function, dosage
of aminoglycosides must be reduced.
Dosages or intervals may be reduced.
In UTIs, may use lower dosage as
excreted by kidneys
Daily dosing
Fluoroquinolones
Synthetic bactericidal drugs with
activity against gram positive and
gram negative organisms
Most are given orally
Excreted via kidneys
Mechanism of action is by interfering
with DNA gyrase, an enzyme
necessary for synthesis of bacterial
DNA
Fluoroquinolones
May be used to treat respiratory, GU,
GI, bones, joints, skin and soft
tissues. Useful in multi-drug resistant
TB, Mycobacterium avium complex
patients, for fever in neutropenic
patients and in tx of gonorrhea.
Fluoroquinolones cont.
Contraindicated in hypersensitivity
reactions
In children under 18 years of age
In pregnant or lactating women
Examples of quinolones: Cipro
(ciprofloxacin), Levaquin
(levofloxacin), Floxin (ofloxacin)
Pregnancy category C
Fluoroquinolones cont.
Monitor renal and liver function
Ensure adequate fluid intake to
prevent crystalluria
Assess current medications for drugs
that interact with
Avoid exposure to sunlight
Macrolides
Include: Zithromax (azithromycin),
Biaxin (clarithromycin), EES
(erythromycin) and Dynabac
(dirithromycin)
Effective against gram positive cocci,
Neisseria, Treponema,
Mycoplasma,Bacteroides, Clostridia
and Corynebacterium
Macrolides
Erythromycin is the prototype
Food can have an effect on absorption
New relative, Ketek (telithromycin)
called ketolides. Will offer better
activity against multi-drug resistant
strains of Streptococcus.
Macrolides
Mechanism of action is by entering
microbial cells and attaching to 50S
ribosomes, thereby inhibiting
microbial protein synthesis
EES is PCN alternative
Indications for Macrolides
Respiratory tract infections
Skin and soft tissue infections caused
by Staph and Strep
For Legionnaire’s and GU infections
caused by Chlamydia
Clarithromycin is indicated for tx of
MAC and for H. pylori
Macrolide Management
Considerations
EES interferes with the elimination of
drugs metabolized by the cytochrome
P450 enzymes
Interacting drugs include: Coumadin,
Theophylline, Prednisone, Norpace,
Lanoxin, Tegretol, Alfenta and
Parlodel (dopamine agonist)
Macrolides
Contraindicated in liver disease
Contraindicated in hypersensitivity
Miscellaneous Antibacterials
Chloramphenicol—broad spectrum
bacteriostatic used for gram negative
and positive bacterial infections
More toxic than others that can do
equally well for gram positives
Indicated in meningococcal,
pneumococcal, rickettsial infections
and in Haemophilus and Klebsiella
Miscellaneous
Cleocin (clindamycin)—similar in actio
to macrolides; is effective against
gram positive cocci and pneumococci
Effective in treating mixed infections
Great for acne and bacterial vaginosis
Can cause pseudomembranous colitis
Miscellaneous
Zyvox (linezolid) is a member of the
oxalodinone class
Active against aerobic gram positive
bacteria
Indicated for septicemia
Can cause myelosuppression and
psedomembranous colitis
Miscellaneous
Flagyl (metronidazole)
Effective against anaerobic bacteria,
gram positive bacilli such as
clostridium and protozoa such as
Giardia, amebiasis, trichomoniasis
Useful topically for rosacea
Used for bacterial vaginosis
Disulfiram-like reaction if taken
w/alcohol
Miscellaneous--Vancomycin
Active against gram positives only
Frequently used to treat MRSA
Can cause hypotension, flushing and
skin rash if given too quickly
Resistance is mounting
Can cause “red man sydrome” if
given too quickly
Caution in patients w/myasthenia
gravis
Drug interactions
Amphotericin B, vancomycin,
cephalosporins, loop diuretics,
neuromuscular blocking agents can
increase the effects of
aminoglycosides
Tagamet (cimetidine) and Probenecid
increase the effects of the
fluoroquinolones
Drug Interactions cont.
Chloramphenicol and Streptomycin
increase the effects of EES
Tagamet increases the action of Flagyl
Others, see text
Syndercid (quinupristindalfopristin)
Effective in vancomycin resistant
strains MRSA
Strong inhibitor of cytochrome P450
Belong to a class called
streptogramins
Caustic to veins
Tetracyclines
Broad spectrum bacteriostatic
Microbial resistance emerging
Newer options less toxic
Still very effective against rickettsiae
(e.g. Rocky Mountain Spotted Fever)
Effective against Chlamydia,
Mycoplasma, protozoa (e.g. Malaria,
Giardia, Leishmaniasis)
Tetracyclines
Most are excreted in urine
Examples include: Minocin
(minocycline), Vibramycin
(doxycycline), Achromycin
(tetracycline)
Tetracyclines
Work by passive diffusion and an
active transport system
Bind to 30S ribosomes and inhibit
micorbial protein synthesis
Drugs of choice in Brucellosis,
Chancroid, Cholera, Granuloma
Inguinale, Trachoma, H. pylori
Indications for use
Treatment of uncomplicated urethral,
endocervical or rectal infections
caused by chlamydia
Adjunt in the treatment of PID and
STDs
Long term treatment of acne
(interfere with production of free fatty
acids and Corynebacterium in sebum)
Indications for use on tetracyclines
cont.
May be used as substitute for
penicillin
Doxycycline may be used for
Traveller’s diarrhea
Declomycin (demeclocycline) may be
used to inhibit ADH in management of
chronic SIADH
Tetracyclines cont.
Contraindicated in renal failure except
for doxy and minocycline
Not indicated in children less than 8
years of age because can cause
permanent discoloration of teeth and
can depress bone growth
Can cause photosensitivity
Avoid taking within 2 hours of dairy
products, w/iron or w/antacids
Sulfonamides
Bacteriostatic against both gram
positive and gram negative bacteria
Resistance is mounting
Combination of Bactrim
(trimethoprim-sulfamethoxazole) is
useful in the treatment of urinary
tract infections and in Pneumocystis
carinii
Sulfonamide preparaions
Azulfidine (sulfasalazine) is used in
tx of ulcerative colitis and in RA
May cause crystalluria. Liberal fluids
needed.
Sulfonamides cont.
Sulfamylon used in burns—especially
w/Pseudomonas—can cause
metabolic acidosis, is painful
w/application
Silver sulfadiazine—useful in burns
Miscellaneous Drugs for UTIs
Macrodantin (nitrofurantoin)
Pyridium (phenazopyridine)-no
antibacterial activity, acts as urinary
antiseptic
Questions?
Sulfonamides
Contraindicated in renal failure
Can cause bone marrow depression,
especially in elderly
With Bactrim, can cause folic acid
deficiency
Can cause cholestatic jaundice in rare
cases