Pharm 87
Aminoglycosides Drug interactions
-beneficial -adverse
Gentamicin adverse effects
-nephrotoxicity -ototoxicty
Aminoglycosides Adverse effects
Adverse effects -Nephrotoxicity -Ototoxicity (total cumulative and trough levels) -Hypersensitivity reactions -Neuromuscular blockade: -----Concurrent use with neuromuscular blocking agents, general anesthetics, and in myasthenia gravis Treatment of choice: Reversal with IV infusion of a calcium salt (eg, calcium gluconate) Hypersensitivity reactions Blood dyscrasias Others
The patient is ordered daily divided doses of gentamycin. The patient received an intravenous dose of gentamycin at 4:00 pm. When should the nurse obtain the peak level? A. 4:30 pm B. 5:00 pm C. 5:30 pm D. 6:00 pm
Answer: A Rationale: When using divided daily doses, draw blood samples for measuring peak levels 1 hour after IM injection and 30 minutes after completing an IV infusion. When a single daily dose is used, measuring peak levels is unnecessary. Draw samples for trough levels just before the next dose (when using divided daily doses) or 1 hour before the next dose (when using a single daily dose).
Before administering gentamycin, it is most important for the nurse to assess the patient for a history of what? A. Hypertension B. Myasthenia gravis C. Diabetes mellitus D. Asthma
Answer: B Rationale: Aminoglycosides must be used with caution in patients with renal impairment, pre-existing hearing impairment, and myasthenia gravis, and in patients receiving ototoxic drugs (especially ethacrynic acid), nephrotoxic drugs (eg, amphotericin B, cephalosporins, vancomycin, cyclosporine, nonsteroidal anti-inflammatory drugs [NSAIDs]), and neuromuscular blocking agents.
The nurse is reviewing laboratory values from a patient who has been prescribed gentamicin. To prevent ototoxicity, it is most important for the nurse to monitor which value(s)? A. Serum creatinine and blood urea nitrogen levels B. Trough drug levels of gentamicin C. Peak drugs levels of gentamicin D. Serum alanine aminotransferase and aspartate aminotransferase levels
Answer: B Rationale: To minimize ototoxicity, trough levels must be sufficiently low to reduce exposure of sensitive sensory hearing cells. The risk of ototoxicity is related primarily to persistently elevated trough drug levels rather than to excessive peak levels.
The nurse is caring for a patient receiving intravenous gentamicin for a severe bacterial infection. Which assessment finding by the nurse indicates the patient is experiencing an adverse effect of gentamycin therapy? A. Blurred vision B. Hand tremors C. Urinary frequency D. Tinnitus
Answer: D Rationale: Ototoxicity can result from accumulation of the drug in the inner ear. Early signs that should be reported include tinnitus or headache. Other major adverse effects include nephrotoxicity and neuromuscular blockade.
Serum levels
Dosing -Single large dose each day or 2 or 3 smaller doses Monitoring of serum levels is common; the same aminoglycoside dose can produce very different plasma levels in different patients Peak levels must be high enough to kill bacteria; trough levels must be low enough to minimize toxicity
Aminoglycosides
Most commonly used agents -Gentamicin, tobramycin, amikacin Narrow-spectrum antibiotics Bactericidal Use: Aerobic gram-negative bacilli Can cause serious injury to inner ear and kidney Not absorbed from GI tract Microbial resistance
Peak and Trough Levels
Samples for peak levels should be taken 30 minutes after giving an IM injection or after completing a 30-minute IV infusion Sampling for trough levels depends on the dosing schedule -Divided doses: Take sample just before the next dose -Once-daily doses: Draw a single sample 1 hour before the next dose; value should be very low—preferably close to zero
Gentamicin [Garamycin] uses
Used to treat serious infections caused by aerobic gram-negative bacilli -Pseudomonas aeruginosa -Escherichia coli -Klebsiella -Serratia -Proteus mirabilis
Trough High
lower dose