Pharm Chapter 39: Antibiotics Part 2

Other drugs

-Clindamycin is contraindicated in patients with a known hypersensitivity to it, those with ulcerative colitis or enteritis, and infants younger than 1 month of age. -Metronidazole (Flagyl) is an antimicrobial drug of the class nitroimidazole, has good activity against anaerobic organisms, and is widely used for intra-abdominal and gynecologic infections; it is also used to treat protozoal infections (e.g., amebiasis, trichomoniasis). -Linezolid (Zyvox) is the rst antibacterial drug in a new class of antibiotics known as oxazolidinones. This drug works by inhibiting bacterial protein synthesis. Linezolid was originally developed to treat infections associated with VRE. Vancomycin can cause additive neuro- muscular-blocking effects in those taking neuromuscular blockers, assess for hx of renal disease or hearing loss

Aminoglycosides

-a group of natural and semisynthetic antibiotics that are classified as bactericidal drugs, are very potent, and are capable of potentially serious toxicities (e.g., nephrotoxicity, ototoxicity). -Aminoglycosides include amikacin, gentamicin, and tobramycin. -Serum levels of aminoglycosides are routinely monitored and dosages are adjusted to maintain optimal levels that maximize drug efficacy and minimize the risk for toxicity. This process is called therapeutic drug monitoring. -Aminoglycoside therapy is commonly monitored in this way due to the nephrotoxicity and ototoxicity associated with these drugs. -Dosing is adjusted to the patient's level of renal function based on estimates of creatinine clearance calculated from serum creatinine values. The serum level needs to be at least eight times higher than the minimum inhibitory concentration (MIC), which is a measure of the lowest concentration of drug needed to kill a certain standard amount of bacteria. This value is determined in vitro for each drug. -Beta-lactams act through time-dependent killing; the amount of time the drug is above the MIC is critical for maximal bacterial kill. Aminoglycosides work primarily through concentration-dependent killing; achieving a drug plasma concentration that is a certain level above the MIC, even for a brief period of time, results in the most effective bacterial kill. -Once-daily dosing provides a sufficient plasma drug concentration for bacterial kill, along with equal or lower risk for toxicity compared with multiple daily dosing regimens. Use of a once-daily regimen also reduces the nursing care time required and often allows for outpatient or even home-based aminoglycoside drug therapy. Trough (lowest) levels are measured to ensure adequate renal clearance and avoid toxicity. -The therapeutic goal is a trough concentration at or below 1 mcg/mL. Trough levels above 2 mcg/mL are associated with a greater risk for both ototoxicity and nephrotoxicity. • Aminoglycosides work in a manner similar to that of the tetracyclines in that they bind to ribosomes, specifically the 30S ribosome, and prevent protein synthesis in bacteria. • Aminoglycosides are most often used in combination with other antibiotics such as beta-lactams or vancomycin because the combined effect of the two antibiotics is greater than the sum of the effects of each drug acting separately. This is known as a synergistic effect. • Aminoglycosides also have a property known as the postantibiotic effect; continued bacterial growth suppression occurs after short-term antibiotic exposure, as in once-daily dosing. • Toxicity associated with aminoglycosides limits their use to treatment of serious gram-negative infections and specific conditions involving gram-positive cocci, in which case gentamicin is usually given in combination with a penicillin. • Gram-negative infections treated with aminoglycosides include those caused by Pseudomonas species and several organisms belonging to the Enterobacteriaceae family, including Escherichia coli, Proteus spp., Klebsiella spp., and Serratia spp. • Aminoglycosides are also used for prophylaxis in procedures involving the gastrointestinal (GI) or genitourinary (GU) tract because such procedures carry a high risk for enterococcal bacteremia. • Aminoglycosides are to be administered with caution in premature and full-term neonates because of their renal immaturity. • Aminoglycosides are very potent antibiotics and are capable of potentially serious toxicities, especially to the kidneys and to the ears, in which they can affect hearing and balance functions. Duration of drug therapy needs to be as short as possible, based on sound clinical judgment and monitoring of the patient's progress.

Quinolones

-very potent bactericidal broad-spectrum antibiotics and include norfloxacin, ciprofloxacin, levofloxacin, and moxifloxacin. With the exception of norfloxacin, these antibiotics have excellent oral absorption. • Quinolone antibiotics destroy bacteria by altering their DNA. • Quinolones are active against a wide variety of gram- negative and selected gram-positive bacteria. Most are excreted by the kidneys as unchanged drug. This, together with the extensive gram-negative coverage, makes them suitable for treating complicated urinary tract infections, as well as respiratory, skin, GI, and bone and joint infections. • The use of quinolones in prepubescent children is not generally recommended because these drugs have been shown to affect cartilage development in laboratory animals. However, judicious use in children might be less of a risk than previously thought, and these drugs are used commonly in children with cystic fibrosis. • Bacterial overgrowth is a complication of quinolones but is more commonly associated with long-term use. More worrisome is a cardiac effect that involves prolongation of the QT interval on the electrocardiogram (ECG). • Concurrent use of quinolones with antacids, calcium, magnesium, iron, zinc preparations, or sucralfate causes a reduction in the oral absorption of the quinolone. • Quinolones can also cause peripheral neuropathy, which may be permanent. New evidence suggests that they may also cause liver injury in older adults. • Probenecid can reduce the renal excretion of quinolones. Nitrofurantoin can antagonize the antibacterial activity of the quinolones, and oral anticoagulants are to be used with caution because of the antibiotic-induced alteration of intestinal flora, affecting vitamin K synthesis.

The nurse is planning care for a client prescribed once-daily IV gentamicin (Garamycin) therapy. When should the nurse schedule a trough drug level to be drawn? A. 12 hours after completing the antibiotic infusion B. 18 hours after completing the antibiotic infusion C. 30 minutes after beginning the antibiotic infusion D. 60 minutes after beginning the antibiotic infusion

A. 12 hours after completing the antibiotic infusion Trough serum drug levels should be drawn at least 8 to 12 hours after the medication is infused.

When providing instructions to clients on use of antibiotics, which instructions would the nurse include in the teaching? (Select all that apply.) A. Complete the entire course of therapy. B. Increase fluid intake up to 3000 mL/day. C. Wash your hands before and after preparing food. D. Notify the provider of any possible reactions that occur. E. Save unused medication in a cool dry place for later use.

A. Complete the entire course of therapy. B. Increase fluid intake up to 3000 mL/day. C. Wash your hands before and after preparing food. D. Notify the provider of any possible reactions that occur. There should not be any leftover medication, but if there is, it needs to be discarded in the appropriate method. The health care provider typically only writes a prescription for the exact amount of medication needed by the client.

The client's culture has grown gram-positive cocci, and the health care provider prescribes two different antibiotics, one of which is gentamicin (Garamycin). To treat this type of infection, which type of antibiotic is typically prescribed together with gentamicin (Garamycin)? A. Penicillin B. Cephalosporin C. Fluoroquinolone D. Aminoglycoside

A. Penicillin In gram-positive cocci, gentamicin is usually given in combination with a penicillin antibiotic. The other antibiotics are not typically prescribed with gentamicin for this culture result.

Nursing Implications

Assess for history of or current symptoms indicative of hypersensitivity or allergic reactions, with symptoms from mild reactions with rash, pruritus, or hives to severe reactions with laryngeal edema, bronchospasm, and hypotension to possible cardiac arrest. • With any antibiotic, assess for superinfection, or a secondary infection that occurs with the destruction of normal flora during antibiotic therapy. • Antibiotic resistance is a concern, especially in pediatrics and in large health care institutions and long-term care facilities. You must consider this possibility of resistance to certain antibiotics when assessing patients for symptoms of infection and superinfection.

When performing discharge teaching for a client prescribed oral linezolid (Zyvox) to treat methicillin-resistant Staphylococcus aureus (MRSA), the nurse should emphasize which important information? A. Stop the drug as soon as you feel better. B. Avoid ingestion of foods containing tyramine. C. Report any occurrence of constipation or facial flushing. D. Take the drug with an antacid to avoid gastrointestinal (GI) upset.

B. Avoid ingestion of foods containing tyramine. Hypertension may occur in clients consuming tyramine-containing foods such as aged cheese or wine, soy sauce, smoked meats or fish, and sauerkraut while taking linezolid. Linezolid causes diarrhea, not constipation, and should be taken with food to decrease GI distress. An antacid would interfere with absorption.

For a client receiving an intravenous (IV) infusion of gentamicin (Garamycin), the nurse would monitor which laboratory values? A. Hematocrit and hemoglobin B. Blood urea nitrogen (BUN) and creatinine C. Prothrombin time and partial thromboplastin time D. Serum glutamic-oxaloacetic transaminase and alanine transaminase

B. Blood urea nitrogen (BUN) and creatinine Gentamicin has a high potential for nephrotoxicity. Nephrotoxicity typically occurs in 5% to 25% of clients. Thus, the client's renal function test results for BUN and creatinine must be monitored closely throughout therapy.

A client who is prescribed metronidazole (Flagyl) for a gynecologic infection provides the nurse with a list of medications that are routinely taken. Which medication would lead the nurse to question the prescription for Flagyl? A. Ibuprofen (Advil) B. Lithium (Eskalith) C. Levothyroxine (Synthroid) D. Multivitamin (Thera-Tabs)

B. Lithium (Eskalith) Concomitant use of lithium and metronidazole may result in lithium toxicity. Thus, a client who reports taking lithium should alert the nurse to notify the health care provider because of the potential significant interaction.

The nurse would teach a client prescribed metronidazole (Flagyl) to avoid ingestion of which drink? A. Milk B. Wine C. Coffee D. Orange juice

B. Wine A disulfiram-like (Antabuse) reaction may occur with concurrent ingestion of metronidazole and alcohol, leading to facial flushing, tachycardia, palpitations, nausea, and vomiting.

The nurse should assess a client for nephrotoxicity and ototoxicity when administering which antimicrobial? A. Cefazolin (Ancef) B. Clindamycin (Cleocin) C. Gentamicin (Garamycin) D. Erythromycin

C. Gentamicin (Garamycin) Aminoglycoside antibiotics, including gentamicin, have a high risk for nephrotoxicity and ototoxicity.

Quinolones are a class of antibiotics known for several significant complications. Which are possible adverse effects with these drugs? (Select all that apply.) A. Ototoxicity B. Nephrotoxicity C. Tendon rupture D. Prolongation of the QT interval E. Abnormal cartilage development in children

C. Tendon rupture D. Prolongation of the QT interval E. Abnormal cartilage development in children Quinolones are not used in prepubescent children because of the risk of cartilage development issues. Quinolones may also cause a cardiac effect that involves prolongation of the QT interval on the electrocardiogram. The use of these medications can result in tendonitis or ruptured tendons in adults. Nephrotoxicity and ototoxicity are not associated with quinolones.

The nurse will question the use of a fluoroquinolone antibiotic in a client already prescribed which medication? A. Furosemide (Lasix) B. Omeprazole (Prilosec) C. Metoprolol (Lopressor) D. Amiodarone (Cordarone)

D. Amiodarone (Cordarone) Dangerous cardiac dysrhythmias are more likely to occur when quinolones are taken by clients receiving class Ia and class III antidysrhythmic drugs such as disopyramide and amiodarone. For this reason, such drug combinations should be avoided.

Which is a complication of vancomycin IV infusions? A. Angioedema B. Neurotoxicity C. Cardiomyopathy D. Red man syndrome

D. Red man syndrome When infused too rapidly, clients receiving vancomycin may develop hypotension accompanied by flushing or itching of the head, face, neck, and upper trunk area. This phenomenon is called red man syndrome.