Aminoglycosides Practice Test

1. Aminoglycosides are not well absorbed from the gut, so they should be delivered via parenteral routes.

True

False

Aminoglycosides are a class of antibiotics that are not well absorbed from the gut when taken orally. Therefore, they are typically administered through parenteral routes such as intravenous or intramuscular injection. This is because parenteral administration ensures direct delivery of the drug into the bloodstream, bypassing the need for absorption from the gastrointestinal tract. By delivering aminoglycosides via parenteral routes, their therapeutic effects can be maximized and systemic distribution can be achieved more effectively.

Explanation

Aminoglycosides are a class of antibiotics that are not well absorbed from the gut when taken orally. Therefore, they are typically administered through parenteral routes such as intravenous or intramuscular injection. This is because parenteral administration ensures direct delivery of the drug into the bloodstream, bypassing the need for absorption from the gastrointestinal tract. By delivering aminoglycosides via parenteral routes, their therapeutic effects can be maximized and systemic distribution can be achieved more effectively.

2. Which of the following drugs is NOT an aminoglycoside?

Neomycin

Azithromycin

Amikacin

Streptomycin

Azithromycin is not an aminoglycoside because it belongs to a different class of antibiotics called macrolides. Aminoglycosides, such as Neomycin, Amikacin, and Streptomycin, are characterized by their structure and mechanism of action, which is different from that of Azithromycin. Aminoglycosides inhibit bacterial protein synthesis by binding to the bacterial ribosome, while Azithromycin works by inhibiting bacterial protein synthesis through a different mechanism. Therefore, Azithromycin is the correct answer as it does not belong to the aminoglycoside class.

Explanation

Azithromycin is not an aminoglycoside because it belongs to a different class of antibiotics called macrolides. Aminoglycosides, such as Neomycin, Amikacin, and Streptomycin, are characterized by their structure and mechanism of action, which is different from that of Azithromycin. Aminoglycosides inhibit bacterial protein synthesis by binding to the bacterial ribosome, while Azithromycin works by inhibiting bacterial protein synthesis through a different mechanism. Therefore, Azithromycin is the correct answer as it does not belong to the aminoglycoside class.

3. Aminoglycosides are effective against what kind of microorganisms?

Anaerobic gram-negative bacteria

Aerobic gram-positive bacteria

Anaerobic gram-positive bacteria

Aerobic gram-negative bacteria

Aminoglycosides are a class of antibiotics that are known to be effective against aerobic gram-negative bacteria. These bacteria have a cell wall structure that allows aminoglycosides to easily penetrate and disrupt their cellular processes. Aminoglycosides work by inhibiting protein synthesis in the bacteria, ultimately leading to their death. They are not as effective against anaerobic gram-negative bacteria or aerobic and anaerobic gram-positive bacteria, as their cell wall structures and metabolic processes are different from aerobic gram-negative bacteria.

Explanation

Aminoglycosides are a class of antibiotics that are known to be effective against aerobic gram-negative bacteria. These bacteria have a cell wall structure that allows aminoglycosides to easily penetrate and disrupt their cellular processes. Aminoglycosides work by inhibiting protein synthesis in the bacteria, ultimately leading to their death. They are not as effective against anaerobic gram-negative bacteria or aerobic and anaerobic gram-positive bacteria, as their cell wall structures and metabolic processes are different from aerobic gram-negative bacteria.

4. Renal damage is a potential adverse effect of aminoglycosides. In which part of the kidney are aminoglycosides retained due to which this effect is caused?

Glomerulus

Distal tubule

Proximal tubule

Loop of Henle

Aminoglycosides are retained in the proximal tubule of the kidney, which leads to renal damage. The proximal tubule is responsible for reabsorbing important substances from the filtrate back into the bloodstream. When aminoglycosides accumulate in this area, they can disrupt the normal functioning of the tubule and cause damage to the renal tissue. This can result in impaired kidney function and potentially lead to renal failure.

Explanation

Aminoglycosides are retained in the proximal tubule of the kidney, which leads to renal damage. The proximal tubule is responsible for reabsorbing important substances from the filtrate back into the bloodstream. When aminoglycosides accumulate in this area, they can disrupt the normal functioning of the tubule and cause damage to the renal tissue. This can result in impaired kidney function and potentially lead to renal failure.

5. Regarding the mechanism of action of aminoglycosides, the drugs

Are bacteriostatic

Bind to the 50S ribosomal subunit

Cause misreading of the code on the mRNA template

Inhibit peptidyl transferase

Stabilize polysomes

Aminoglycosides are bactericidal inhibitors of protein synthesis binding to specific components of the 30S ribosomal subunit. Their actions include block of the formation of the initiation complex, miscoding, and polysomal breakup. Peptidyl transferase is inhibited by chloramphenicol, not aminoglycosides.

Explanation

Aminoglycosides are bactericidal inhibitors of protein synthesis binding to specific components of the 30S ribosomal subunit. Their actions include block of the formation of the initiation complex, miscoding, and polysomal breakup. Peptidyl transferase is inhibited by chloramphenicol, not aminoglycosides.

6. Aminoglycosides have no activity against streptococci.

True

False

Aminoglycosides are a class of antibiotics that are known to be ineffective against streptococci bacteria. This is because aminoglycosides primarily target and inhibit protein synthesis in bacteria, but streptococci have a different mechanism of protein synthesis that is not affected by aminoglycosides. Therefore, aminoglycosides have no activity against streptococci, making the statement "True."

Explanation

Aminoglycosides are a class of antibiotics that are known to be ineffective against streptococci bacteria. This is because aminoglycosides primarily target and inhibit protein synthesis in bacteria, but streptococci have a different mechanism of protein synthesis that is not affected by aminoglycosides. Therefore, aminoglycosides have no activity against streptococci, making the statement "True."

7. All the following statements about the clinical uses of the aminoglycosides are accurate, except

Effective in the treatment of infections caused by anaerobes such as Bacteroides fragilis

Gentamycin is used with ampicillin for synergistic effects in the treatment of enterococcal endocarditis.

In the treatment of a hospital-acquired infection caused by Serratia marcescens, netilmicin is more effective than streptomycin.

Often used with cephalosporins in the empiric treatment of life-threatening bacterial infections.

Owing to their polar nature, aminoglycosides are not absorbed after oral administration.

Aminoglycoside antibiotics act at the ribosomal level, and their intracellular accumulation by bacteria are oxygen dependent. Anaerobic bacteria, including B fragilis, are innately resistant.

Explanation

Aminoglycoside antibiotics act at the ribosomal level, and their intracellular accumulation by bacteria are oxygen dependent. Anaerobic bacteria, including B fragilis, are innately resistant.

8. Which statement is accurate regarding the antibacterial action of the aminoglycoside amikacin?

Antibacterial activity is often reduced by the presence of an inhibitor of cell wall synthesis.

Antibacterial action is not concentration-dependent.

Antibacterial action is time-dependent.

Efficacy is directly proportional to the duration of time that the plasma level is greater than the minimal inhibitory concentration.

The drug continues to exert antibacterial effects even after plasma levels decrease below detectable levels.

The antibacterial action of aminoglycosides is concentration dependent rather than time-dependent. The activity of amikacin continues to increase as its plasma level rises above the minimal inhibitory concentration (MIC). When the plasma level falls below the MIC, aminoglycosides continue to exert antibacterial effects for several hours, exerting a post-antibiotic effect. Inhibitors of bacterial cell wall synthesis often exert synergistic effects with aminoglycosides, possibly by increasing the intracellular accumulation of the aminoglycoside.

Explanation

The antibacterial action of aminoglycosides is concentration dependent rather than time-dependent. The activity of amikacin continues to increase as its plasma level rises above the minimal inhibitory concentration (MIC). When the plasma level falls below the MIC, aminoglycosides continue to exert antibacterial effects for several hours, exerting a post-antibiotic effect. Inhibitors of bacterial cell wall synthesis often exert synergistic effects with aminoglycosides, possibly by increasing the intracellular accumulation of the aminoglycoside.

9. A 72-kg patient with creatinine clearance of 80 mL/min has a gram-negative infection. Amikacin is administered intramuscularly at a dose of 5 mg/kg every 8 h, and the patient begins to respond. After 2 d, creatinine clearance declines to 40 mL/min. If no information is available about amikacin plasma levels, what would be the most reasonable approach to the management of the patient at this point?

Administer 5 mg/kg every 12 h

Decrease the dosage to a daily total of 200 mg

Decrease the dosage to 180 mg every 8 h

Discontinue amikacin and switch to gentamicin

Maintain the patient on the present dosage and test auditory function

Monitoring plasma drug levels is important when aminoglycosides are used. In this case, the patient seems to be improving, so a decrease of the amikacin dose in proportion to decreased creatinine clearance is most appropriate. Because creatinine clearance is only one-half of the starting value, a dose reduction should be made to one-half of that given initially.

Explanation

Monitoring plasma drug levels is important when aminoglycosides are used. In this case, the patient seems to be improving, so a decrease of the amikacin dose in proportion to decreased creatinine clearance is most appropriate. Because creatinine clearance is only one-half of the starting value, a dose reduction should be made to one-half of that given initially.

10. An adult patient (weight 80 kg) has bacteremia suspected to be due to a gram-negative rod. Tobramycin is to be administered using a once-daily dosing regimen, and the loading dose must be calculated to achieve a peak plasma level of 20 mg/L. Assume that the patient has normal renal function. Pharmacokinetic parameters of tobramycin in this patient are as follows: Vd = 30 L; t1/2 = 3 h; CL = 80 mL/min. What should the loading dose be given?

100 mg

200 mg

400 mg

600 mg

800 mg

The loading dose of any drug is calculated by multiplying the desired plasma concentration (mg/L) by the volume of distribution (L).

Explanation

The loading dose of any drug is calculated by multiplying the desired plasma concentration (mg/L) by the volume of distribution (L).