Is Amikacin (an aminoglycoside antibiotic) 250mg administered via Intramuscular (IM) injection, twice a day (BID), for 5 days, an appropriate dosage for a patient weighing 141 pounds?

From the Guidelines

Amikacin 250mg IM BID x 5 days is not an appropriate regimen for a patient weighing 141 lbs (64 kg) due to the inadequate dose and potential for toxicity. The recommended dosing for amikacin is 10-15 mg/kg per day, adjusted according to drug level monitoring, which would suggest a daily dose of approximately 640-960 mg for this patient 1. The proposed 500 mg daily dose (250 mg twice daily) is significantly below the therapeutic range. Additionally, amikacin is usually administered once daily rather than twice daily due to its concentration-dependent killing and post-antibiotic effect. Renal function assessment is essential before prescribing amikacin as it is nephrotoxic. Therapeutic drug monitoring through peak and trough levels would be necessary to ensure efficacy while avoiding toxicity. The indication for amikacin should also be carefully considered, as it's typically reserved for serious gram-negative infections with limited alternative options due to its potential for ototoxicity and nephrotoxicity.

Some key points to consider when prescribing amikacin include:

• Weight-based dosing: 10-15 mg/kg per day
• Administration: once daily, rather than twice daily
• Renal function assessment: essential before prescribing
• Therapeutic drug monitoring: necessary to ensure efficacy and avoid toxicity
• Indication: typically reserved for serious gram-negative infections with limited alternative options

It's also important to note that amikacin can be administered intravenously (IV) or intramuscularly (IM), and the dosing frequency may vary depending on the specific infection being treated and the patient's renal function 1. However, the proposed regimen of 250mg IM BID x 5 days is not supported by the current evidence and may put the patient at risk for toxicity or treatment failure.

In general, the use of amikacin should be carefully considered and guided by the most recent and highest quality evidence, taking into account the patient's specific clinical situation and the potential risks and benefits of treatment 1.

From the FDA Drug Label

DOSAGE GUIDELINES ADULTS AND CHILDREN WITH NORMAL RENAL FUNCTION Patient WeightDosage lbskg7.5 mg/kg5 mg/kg q12hORq8h ... 132 60 450 mg 300 mg 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 209 95 712. 5 mg 475 mg 220 100 750 mg 500 mg

For a patient weighing 141 lbs, the recommended dosage is between 487.5 mg and 525 mg every 12 hours for a patient with normal renal function. The dosage of 250 mg IM BID is lower than the recommended dose, which is 487.5 mg or 525 mg every 12 hours for a patient weighing 141 lbs with normal renal function 2. Amikacin 250mg IM BID x 5 days may not be sufficient for a patient weighing 141 lbs. It is recommended to adjust the dosage according to the patient's weight and renal function.

From the Research

Amikacin Dosage Evaluation

• The patient's weight is 141 Lbs, which is approximately 64 kg.
• The prescribed dosage is 250mg IM BID x 5days, which translates to 7.8 mg/kg/day for a 64 kg patient, considering the dosage is divided into two doses per day.
• According to the study 3, the dosage of 7.5 mg of amikacin/kg every 12 hr was administered intramuscularly to 32 patients, which is similar to the prescribed dosage.
• However, the study 4 suggests that the half-life of amikacin should be derived from values of rates of creatinine clearance or be predicted with use of a nomogram to ensure therapeutic levels of drug and avoid potentially toxic accumulation of antibiotic.
• The study 5 provides pharmacokinetic parameters for amikacin in patients with normal or impaired renal function, but does not provide a clear recommendation for dosage adjustment based on weight alone.
• The study 6 evaluates amikacin dosage regimens for the management of mycobacterial infections and suggests that standard amikacin dosing guidelines may not achieve target concentrations, but does not provide a direct recommendation for the prescribed dosage.
• The study 7 examines the effects of N-acetylcysteine on renal function and morphology in mice subjected to amikacin-induced nephrotoxicity, but does not provide a direct recommendation for the prescribed dosage.

Considerations for Dosage Adjustment

• The patient's renal function should be considered when evaluating the appropriateness of the prescribed dosage, as impaired renal function can significantly affect amikacin pharmacokinetics 5, 4.
• The study 4 suggests that the half-life of amikacin should be derived from values of rates of creatinine clearance or be predicted with use of a nomogram to ensure therapeutic levels of drug and avoid potentially toxic accumulation of antibiotic.
• The prescribed dosage may be appropriate for a patient with normal renal function, but dosage adjustment may be necessary for patients with impaired renal function 5, 4.