chp 39 study guide: antibiotics affecting the bacterial cell wall
Your patient with a GI infection is prescribed vancomycin by mouth. The patient states, "My friend had this drug, but she got it in her veins. Isn't that a better way to get it?" What is your response?
"Since your problem is in your GI system, giving the drug this way will have a localized action on the infection." -Vancomycin is poorly absorbed, so it has a local effect when given orally
Your patient is prescribed penicillin V for a dental infection. Which of the following instructions would you give?
"Take the medication 1 hour before or 2 hours after a meal." -Penicillin should be taken on an empty stomach.
beta-lactam
active chemical structure of many antibiotics
Your patient is hospitalized with bacteremia. He is prescribed IV ticaricllin and gentamicin. How would you administer these drugs?
wait at least 2 hours between administration of these drugs -These drugs must be given at least 2 hours apart to avoid inactivating each other.
Your patient is to be discharged on cefazolin, a cephalosporin. The nurse should teach the patient to avoid which of the following while taking this drug?
wine, potassium chloride elixirs (such as Kay Ciel), cough medicine -Alcoholic beverages and products con- taining alcohol should be avoided because a disulfiram-like reaction (or alco- hol intolerance) may occur, making the patient feel quite ill. Elixirs always have alcohol in them, and OTC cough medi- cines frequently have alcohol in them.
Your patient is receiving IV vancomycin. To minimize adverse effects, the health care provider has ordered peak-and-trough blood levels. When is the optimal time for you to obtain the peak blood level?
1 hour after the completion of the infusion -Peak levels of the drug circulate 1 hour after the completion of the infusion.
Generally speaking, cephalosporin antibiotics should be taken for
7 to 10 days -Optimal duration for complete eradication of the microbe is 7 to 10 days.
Your patient has a mixed infection and is receiving cefazolin, a cephalosporin, and gentamicin, an aminoglycoside antibiotic. To minimize adverse effects, the nurse should most closely monitor which lab value?
BUN - Blood urea nitrogen (BUN) is a measure- ment of kidney function. Nephrotoxicity is more likely to occur when the patient takes more than one drug that may cause nephrotoxicity; in this case, those drugs are cefazolin and gentamicin. The nurse should also monitor creatinine levels to assess renal function. Hematocrit is not affected by cefazolin therapy. Blood coagulation time, aPTT (active partial thromboplastin time), is altered only if the patient is receiving oral anticoagu- lants, such as warfarin, and cefazolin. Cefazolin is not a drug that the blood levels indicate a therapeutic or toxic level, and cefazolin levels are not mea- sured. However, gentamicin levels are monitored.
Your 86-year-old patient has pneumonia and is prescribed penicillin. She has a history of renal insufficiency. Which of the following lab tests should be done before initiating therapy?
BUN and creatinine -BUN and creatinine are the appropriate lab tests to evaluate renal function.
Your patient has just received an injection of IM procaine penicillin. Within 30 seconds, the patient becomes confused and agitated and runs from the exam room. You suspect
a procaine reaction -Unusual behaviors such as those described indicate a procaine reaction. Allergy to penicillin usually manifests in shortness of breath, rash, hives, urticaria, etc.
Cefazolin, the prototype cephalosporin, is a first generation drug. Most frequent adverse effects are hypersensitivity and GI; nephro- toxicity is possible and is more likely if the patient is also receiving
aminoglycoside anti- biotics. Acute alcohol intolerance, disulfiram- like reaction may occur as an interaction of cefazolin and alcohol.
beta-lactam antibiotics are so called because their chemical structure contains a beta-lactam ring, which is required for
antibacterial action. penicillins, cephalosporins, monobactams, carbapenems, and beta-lactamase inhibitors are all considered beta-lactam antibiotics
resistance to beta-lactams may occur because of the bacteria's ability to produce beta-lactamase. clavulanic acid, tazobactam, and sulbactam are beta-lactamase inhibitors that
are combined with penicillins to eradicate the microbe despite its ability to produce beta-lactamse
Your patient has an order for IV cefazolin (Kefzol). As you take the medication out of the refrigerator, you note that the solution was reconstituted yesterday. You should
call the pharmacy and have a replacement sent Reconstitution of this drug yesterday makes it "outdated," so it should not be used.
Penicillin has a cross sensitivity to which of the following drug classes?
cephalosporins -5% to 10% of patients allergic to penicillins will also be allergic to cephalosporins.
bacterial cell envelope
composed of a thick cell wall and cytoplasmic membrane
patients allergic to one penicillin should be considered allergic to all penicillins. carbapenems also have a beta-lactam ring structure and may create a
cross-sensitivity in patients allergic to a penicillin. monobactam antibiotics have a significantly different chemical structure from other beta-lactams and are safe to give to penicillin-allergic patients
You are to administer the first IV dose of penicillin G to treat a patient's pneumonia. To minimize adverse effects, you should
determine if a sputum culture and sensitivity has been obtained, ask her if she has any drug allergies, monitor her closely during drug administration -Before beginning antibiotic therapy, a culture and sensitivity should be obtained, if at all possible, to determine the exact organism present and which drug therapy will be effective in eradi- cating the organism. A sputum culture would be appropriate for pneumonia. It is important to always verify with patients that they are not allergic to a medication when you administer the first dose. This is especially true with penicillins because anaphylactic reactions are possible drug allergy responses. Because of pos- sible drug allergies, observe the patient closely during the first 30 minutes of drug administration for signs of adverse effects.
Before the administration of penicillin, it is important to
determine if any previous reactions to antibiotics have occurred -Patients may have forgotten to report that they have a penicillin allergy. It is prudent to ask before initiation of therapy.
drugs that affect the bacterial cell wall penetrate the cell wall and bind to molecular targets on the cytoplasmic membrane in the cell. they then disrupt the strength of the cell wall. this permits the high oncotic pressure inside the cell to
draw fluid into the cell. fluid is drawn in until the cell bursts. the patient's immune system cleans up the debris and fights any remaining infection
beta-lactamases
enzymes that disrupt the beta-lactam ring
penicillinases
enzymes that inactivate penicillin
cephalosporinases
enzymes that inactive cephalosporins
Vancomycin, a tricyclic glycopeptide antibi- otic, is the only drug in its class. In addition to altering the bacterial cell wall, it inhibits the synthesis of RNA. Because of serious toxicity, vancomycin is used only in
erious infections when other antibiotics have failed. Vancomycin-resistant enterococci (VRE) is becoming a common problem.
Vancomycin has adverse effects of neph- rotoxicity, ototoxicity, and significant his- tamine release (resulting in anaphylactoid reactions and "red man" or "red neck" syndrome). Administer drug slowly IV (at least over 60 minutes), and avoid
extravasa- tion. Monitor the peak or trough levels and hepatic and renal function. Assess for change in balance and hearing loss.
In contrast to narrow-spectrum penicillins, aminopenicillins such as amoxicillin (Amoxil) have increased effectiveness against
gram-negative bacteria infections -Aminopenicillins have an altered side chain that makes them effective against many gram-negative microorganisms.
Imipenem, meropenem, ertapenem, and doripenem are the carbapenems approved for use in the United States. They are very broad- spectrum antibiotics with activity against
gram-positive cocci, gram-negative cocci, and bacilli, and they are the most effective beta-lactam antibiotics for use against anaerobes
penicillins were the first antibiotics used clinically. they are classified as narrow spectrum, broad spectrum, or extended spectrum; they may also be penicillinase resistant. penicillin G aqueous, the prototype penicillin, is a narrow-spectrum, bactericidal drug that is effect against mostly
gram-positive organisms. it is most commonly given IN. the most serious adverse effect is allergic reactions. most common adverse effects are GI. for optimum effectiveness, administer .doses around the clock. assess patients carefully, especially during the first dose, for allergic reactions.
Your patient has been receiving IV cefazo- lin for the past 24 hours, and the next dose is now due. You note that the culture and sensitivity test results indicate the infection is resistant to cephalosporins. You should
hold the cefazolin, contact the health care provider, and get an order for a new antibiotic -It is important to get an appropriate order from the physician as soon as pos- sible to get the infection under control. Some hospital policies may direct the nurse to continue the cephalosporin until the prescriber discontinues the medication.
What is the difference between imipenem (Primaxin) and meropenem (Merrem)?
imepenem is easily inactivated and must be administered with cilastatin Imipenem (Primaxin) is rapidly inac- tivated by renal dehydropeptidase 1. Therefore, imipenem is always adminis- tered with cilastatin, a drug that inhibits this enzyme. This does not occur with other carbapenems
You are caring for an 80-year-old patient who has a respiratory infection caused by VRE. The patient also has chronic renal failure. The patient has been prescribed daptomycin to treat the infection. You would expect to administer to this patient
less than the standard adult dose -Daptomycin is excreted mostly unchanged through the urine. Patients with renal disease need to have a decreased dose for this reason. Daptomy- cin, unlike other antibiotics, is used to treat VRE infections.
You are to administer procaine penicillin to a patient in the outpatient department who has syphilis. To maximize therapeutic effects and minimize adverse effects, you should
locate anatomic landmarks to determine the injection site -Procaine penicillin is administered by IM injection. As with all penicillins, it is important to identify an injection site accurately to prevent accidental admin- istration into a vein or nerve. Accidental injection into a vein may precipitate a reaction with the procaine that is in the drug. Procaine penicillin, like all penicil- lins, should be administered deep into a large muscle. The deltoid is too small to be appropriate. Because procaine peni- cillin is thick and viscous, it is adminis- tered more easily if it is removed from the refrigerator about 15 minutes before administration.
penicillin-binding proteins
located inside the bacterial cell wall
Hypersensitivity to cephalosporins frequently presents with
maculopapular rash -Hypersensitivity presents most frequently as a maculopapular rash that develops several days after the onset of therapy.
A benefit of aztreonam (Azactam) therapy is that it
may be used in penicillin-allergic patients -The structure of aztreonam (Azactam) differs substantially from those of other beta-lactam antibiotics; thus, there is little cross-sensitivity, and this drug may be given safely to patients allergic to penicillin.
Generally speaking, penicillin-G is ineffective in the management of
most gram-negative bacteria infections -Only a few gram-negative bacteria respond to penicillin G.
The most serious adverse effects to vancomy- cin are
ototoxicity and nephrotoxicity -Ototoxicity can take the form of cochlear toxicity or vestibular toxicity. Nephrotox- icity is more likely to occur in patients receiving other nephrotoxic drugs.
Your patient is scheduled to receive IV vanco- mycin. To safely administer this medication, you should infuse it
over 60 minutes -This rate will diminish effects such as flushing, tachycardia, hypotension, or rashes that occur when administration is too fast.
Which of the following classes of antibiotics is most likely to induce an allergic reaction?
penicillins -Although all antibiotics may induce an allergic response, penicillin allergies occur most frequently.
Extended-spectrum penicillins are extremely effective against
pseudomonas -The extended penicillins are also known as "antipseudomonal penicillins" because they are effective against Pseudomonas
Vancomycin is used in the management of
serious systemic bacterial infections -Vancomycin is used primarily for sys- temic infections that have not been resolved by less toxic antibiotics.
Your patient is receiving vancomycin as treatment for endocarditis. To minimize adverse effects from the drug therapy, the nurse should administer the drug by
slow IV infusion -Vancomycin should be administered over at least 60 minutes to decrease the risk of ototoxicity and red man syndrome. Intravenous push would be too concen- trated and too fast and would produce adverse effects. Vancomycin is extremely irritating to the tissues and should never be given SC. Poor absorption occurs from the oral route; this route is seldom used and is not appropriate for serious infec- tions outside of the GI tract.
What is the major difference between the different "generations" of cephalosporin agents?
spectrum of activity -One of the major differences between the generations is their spectrums of activity, especially against gram-negative bacteria.
Cephalosporins are similar to penicillins in structure and activity. Penicillin-allergic patients have an increased risk of being allergic to cephalosporins. Four genera- tions of cephalosporins have been intro- duced, each with a different
spectrum of activity. Cephalosporins are the most com- monly prescribed antibiotics; this is lead- ing to cephalosporin-resistant bacteria. Cephalosporins all have generic names that begin with "ceph" or "cef".
Which of the following routes is inappropriate for administration of penicillin?
subcutaneous -Penicillin may be given by the oral, intra- muscular, and intravenous routes.
Beta-lactamase inhibitors are given in conjunction with penicillin to
target the enzyme that may decrease the efficacy of penicillin -Beta-lactamase can inactivate the beta- lactam ring, which is responsible for the activity of these antibiotics. Beta-lacta- mase inhibitors stop the inactivation of the beta-lactam ring, thus allowing the penicillin to eradicate the microbe.
To maximize the therapeutic effect of penicil- lin G, you should administer
the drug for at least 2 days after the patient feels better -This helps to ensure that all of the organisms have been killed so that a re- infection does not occur. Administer oral penicillin G on an empty stomach. Doses should be evenly spaced throughout the 24-hour period. Take IV forms of penicil- lin G out of the refrigerator for 15 min- utes before administering.
Your patient comes to the clinic and receives a diagnosis of infection. When asked about allergies, the patient stated, "I have an allergy to penicillin, but I can take ampicillin." With your knowledge about these drugs, you know that
the patient should not take any form of drug with "cilliin" in its name if he has an allergy to penicillin -Patients allergic to one penicillin are allergic to all penicillins. The nurse does not have the authority to change a prescriber's order to another type of antibiotic.
