Is Amikacin (generic name) 640mg administered via Intramuscular (IM) injection every day (qdx) for 5 days an appropriate dosage for a patient weighing 141 pounds?

From the Guidelines

The amikacin dose of 640mg IM daily for 5 days is not appropriate for this patient. For a patient weighing 141 lbs (64 kg), the recommended amikacin dose should be 15-20 mg/kg/day, which equals approximately 960-1280 mg per day, as suggested by the British Thoracic Society guidelines for the management of non-tuberculous mycobacterial pulmonary disease (NTM-PD) 1. However, amikacin requires careful dosing based on renal function and therapeutic drug monitoring due to its potential for nephrotoxicity and ototoxicity. The current dose of 640 mg appears to be underdosed at only about 10 mg/kg/day. Some key points to consider when dosing amikacin include:

• Obesity: It has been suggested that markedly obese patients should have an adjusted dose using ideal body weight plus 40% of the excess weight, as noted in the British Thoracic Society guidelines 1.
• Renal function: Amikacin should be used with caution in patients with renal function impairment because of the increased risk of both ototoxicity and nephrotoxicity, and dosing adjustments are essential in patients with underlying renal insufficiency, as recommended by the MMWR Recommendations and Reports 1. Additionally, amikacin is typically administered intravenously rather than intramuscularly for serious infections, as IM administration can cause significant pain and may have inconsistent absorption. Before administering amikacin, baseline renal function should be assessed, and drug levels should be monitored during therapy. The appropriate regimen would include proper weight-based dosing, consideration of renal function, therapeutic drug monitoring, and evaluation of whether IM administration is truly necessary versus IV administration.

From the FDA Drug Label

The recommended dosage for adults, children and older infants with normal renal function is 15 mg/kg/day divided into 2 or 3 equal doses administered at equally-divided intervals, i.e., 7.5 mg/kg q12h or 5 mg/kg q8h. DOSAGE GUIDELINES ADULTS AND CHILDREN WITH NORMAL RENAL FUNCTION Patient WeightDosage lbskg7.5 mg/kg5 mg/kg q12hORq8h ... 143 65 487.5 mg 325 mg 154 70 525 mg 350 mg 165 75 562. 5 mg 375 mg 176 80 600 mg 400 mg 187 85 637.5 mg 425 mg 198 90 675 mg 450 mg

For a patient weighing 141 lbs, the recommended dose is between 487.5 mg and 562.5 mg every 12 hours, or between 325 mg and 375 mg every 8 hours. The dose of 640 mg every day for 5 days is higher than recommended for a patient of this weight. Adjustment of the dose is necessary to avoid potential toxicity 2.

From the Research

Amikacin Dosage and Nephrotoxicity

• The patient's weight is 141 Lbs, which is approximately 64 kg.
• The prescribed dose is 640mg IM qdx 5days, which translates to a daily dose of 640mg.
• To determine if this dose is appropriate, we need to calculate the dose per kilogram of body weight.
• The dose per kilogram of body weight is 640mg / 64kg = 10mg/kg.
• According to the study 3, the mean daily amikacin dose was 13.04 (4.21) mg/kg, which is higher than the calculated dose for the patient.
• The study 3 also found that the incidence of amikacin-induced nephrotoxicity was lower in noncritically ill patients, and that therapeutic drug monitoring (TDM) may not be necessary in patients with normal kidney function.

Comparison with Other Studies

• The study 4 compared the nephrotoxicity and ototoxicity of amikacin and gentamicin in patients, and found that amikacin may be less nephrotoxic than gentamicin.
• The study 5 evaluated the nephrotoxicity and ototoxicity of amikacin in neonates, and found that the risk of nephrotoxicity was higher with every-48-h administration than with once-daily administration.
• The study 6 reviewed the pathophysiological mechanism and treatment options for aminoglycoside-related nephrotoxicity and ototoxicity, and found that changes in renal function are typically reversible.
• The study 7 found that the choice of drug and dosage regimen are important risk factors for aminoglycoside nephrotoxicity, and that amikacin has less pronounced nephrotoxic effects than gentamicin, netilmicin, or tobramycin.

Considerations for the Patient

• Based on the studies, it appears that the prescribed dose of 640mg IM qdx 5days may be appropriate for the patient, considering their weight and the potential risk of nephrotoxicity.
• However, it is essential to monitor the patient's kidney function and adjust the dose as needed to minimize the risk of nephrotoxicity 3, 7.
• The patient's baseline kidney function and other risk factors for nephrotoxicity should also be taken into account when determining the appropriate dose and monitoring plan 4, 5, 6.