Aminoglycosides
Drug Category Info
Pharmacokinetics
Absorption
Drug Class
MOA
Indications
Contraindications
Distribution
Metabolism
Excretion
Dose Adjustments
PATIENT TEACHING
Parenteral Therapy
Patients with Kidney Disease
NURSING IMPLICATIONS
PREADMINISTRATION ASSESSMENT
ONGOING ASSESSMENT
- Thorough patient medication information is required to identify high risk patient such as those already taking ototoxic drugs, nephrotoxic drugs, and/or muscular blocking agents.
- Past medical history is also pertinent as ahminoglycosides should be used with extreme caution in patients already experiencing renal impairment, hearing impairment, or myasthenia gravis
ADMINISTRATION
- Identify aminoglycoside to be given for treatment of what type of infection and ensure route is appropriate.
-Aminoglycosides must be given parenterally to treat systemic infections. - DO NOT mix ahminoglycosides and penicillins in the same IV solution
- administer IV solutions over intervals of 30 minutes or more
- Monitor trough and peak levels of aminoglycosides in blood samples, kidney function, and inner ear function continually.
LAB ASSESSMENT
Divided Daily Dose:
- draw blood samples 1 hour after IM injection or 30 minutes after IV infusion for peak levels
- draw blood sample just before next dose for trough levels
Single Daily Dose:
- peak samples not needed
- draw sample 1 hour before next dose for trough levels
Draw samples as ordered to monitor BUN, and creatinine clearance to monitor kidney function. Document I/O's
SAFETY ALERT
BENEFICIAL DRUG INTERACTIONS
Treats serious infections due to aerobic gram-negative bacilli
Oral Therapy
Topical Therapy
Gentamicin treats serious infections with certain gram positive cocci
Enterococcus
Staphylococcus aureus
P. aeruginosa
Enterobacteriaceaee
Suppression of bowel flora before elective colorectal surgery
paromycin is used to treat intestinal amebiasis
Used to treat local infections of the eyes, ears. and skin
Reduce the dose size or increase the dose interval to avoid nephrotoxicity
Adverse Drug Reactions
Ototoxic Drugs
Nephrotoxic Drugs
Skeletal Muscle Relaxants
Not Used for Long Term Therapy
Ototoxixity
Nephrotoxicity
Not recommended for patents with....
A hypersensitivity to Aminogycosides
Pre-existing hearing impairment
Myasthenia gravis
Renal Impairment
This drug is a bactericidal drug that is mainly used on aerobic, Gram- bacteria but can be used on some Gram+ bacteria. This is a concentration dependent bactericidal drug - meaning that the rate and extent of bacterial killing will increase as the drug concentration increases.
The mechanism of action here involves interfering with bacterial protein synthesis by binding to the 30S ribosomal subunit. Formation of the "intiation complex" is disrupted which prevents protein synthesis from taking place. Thus, the 30s subunit cannot read the genetic code of the mRNA properly. Incorrect amino acids are then incorporated into the growing peptide chain, which are useless for bacterial growth. This equates to bacterial death.
Exercise caution when using aminoglycosides in combination with other nephrotoxic or ototoxic drugs. Increased nephrotoxicity may occur with amphotericin B, cephalosporins, polymyxins, vancomycin, cyclosporine, and NSAIDs. Increased ototoxic- ity may occur with ethacrynic acid.
Aminoglycosides can inhibit neuromuscular transmission, causing acid paralysis and potentially fatal respiratory depression. The risk of paralysis is increased by con- current use of neuromuscular blocking agents and general anesthetics
Teach patient that the first sign of impending cochlear damage is high-pitched tinnitus (ringing in the ears). Ototoxicity is largely irreversible. To prevent permanent injury, aminoglycosides should be withdrawn at the first sign of damage (ie, tinnitus, persistent headache, or both).
Aminoglycosides can cause acute tubular necrosis, which is usually reversible. To evaluate renal injury, monitor serum creatinine and BUN. If oliguria or anuria develops, withhold the aminoglycoside and notify the prescriber.
Penicillins and aminoglycosides are frequently employed in combination to enhance bacterial kill.
Like the penicillins, cephalosporins and vancomycin weaken the bacterial cell wall, and can thereby act in concert with aminoglycosides to enhance bacterial kill.
ADVERSE DRUG INTERACTIONS
The risk of renal damage is increased by concurrent therapy with other nephrotoxic agents. potentiative nephrotoxicity can occur with amphotericin B, cephalosporins, polymyxins, vancomycin, and cyclosporine, as well as with aspirin and other nonsteroidal antiin amma- tory drugs (NSAIDs)
The risk of injury to the inner ears is signi cantly increased by concurrent use of ethacrynic acid, a loop diuretic that has ototoxic actions of its own. Combining aminoglycosides with two other loop diuretics—furosemide and bumetanide—appears to cause no more ototoxicity than aminoglycosides alone.
Aminoglycosides are mainly excreted by the kidneys through glomerular filtration, but a very small portion of aminoglycosides are excreted through bile. The half life of aminoglycosides range from 2 to 3 hours in patients with normal renal function.
Due to the wide range of interpatient variability, the dosage must be individualized to each patient with the normal dose ranging from 0.5 mg/kg to 25.8 mg/kg. Various factors can affect the therapeutic dose range including age, body fat percentage, and the pathophysiology of the patient. As people age the excretory capacity of their kidneys decreases which can cause the body to take a longer time clearing the drug, therefore the dose should be decreased for elderly patients to reduce the risk of toxicity. In contrast to this, people who are obese have an increase in body weight which correlates to an increase in clearance which may require a higher dose. The main body process that affects dosage is kidney impairments; these patients must have a reduced dosage due to the fact that aminoglycosides are excreted mainly by the kidneys and an impairment could drastically increase the half-life, resulting in toxicity.
Aminoglycosides are distributed throught the body via extracellular fluid, lymph, and by binding to tissues of organs. If aminoglycosides bind to the tissues of kidneys, it can nephrotoxixity because the drug can bind tightly. If aminoglycosides are distributed to the ears through the perilymph and endolymph, it can result in ototoxicity. Aminoglycosides can cross the placenta and cause trauma to the fetus.
Aminoglycosides are not metabolized, but rather excreted in the urine.
Aminoglycosides are poorly absorbed in the GI tract because they are highly polar cations, and thus too water soluble to be absorbed if given orally. Consequently, they are usually given via a parenteral route. Intramuscular absorption in patients except those with critical illness is both rapid and complete. Peak serum concentrations are achieved between 30-60 minutes given through intramuscular injection or intravenous infusion. In certain patients exhibiting critical illness, especially shock, intramuscular absorption is reduced perhaps due to poor tissue perfusion. Toxic levels of accumulation are possible in patients with sustained use, and especially those with renal impairment.