Administering IV Ampicillin: Medication Calculation and Administration

QUESTION

You are to administer a dose of Ampicillin. The order reads 500 mg q6h, IV. Your patient is 20 kg. The formulary states that the recommended dose is: IM, IV: 50 to 200 mg/kg/day divided every 6 hours; maximum daily dose: 8 g/day. Ampicillin comes in powder and requires reconstitution just prior to administration. The injection vials available on your unit are 250 mg, and have the following reconstitution information. The IV administration guidelines for Ampicillin are as follows: Direct IV Injection: For neonates: Administer 125 mg/mL solution undiluted over 3 to 5 minutes. Other: Dilute to a concentration of 100 mg/mL or less in a syringe and administer over at least 3 to 5 minutes at a rate not to exceed 100 mg/minute. For example, administer a dose of 500 mg over at least 5 minutes (1000 mg over at least 10 minutes, 2000 mg over at least 20 minutes). IV Additive: Dilute to a concentration of 100 mg/mL or less a)What is the lowest safe daily dose for this patient according to the formulary guidelines b)What is the highest safe daily dose for this patient according to the formulary guidelines c) Is this an appropriate order for your patient based on the formulary recommendations? Medication Calculation Questions Vial Size Sterile Water Required Concentration 250 mg 1.9 mL 125 mg/mL Syringe Pump in NS or D5W 50 mL minibagNS or D5W up to the maximum dose of 4000 mg in 40 mL up to the maximum dose of 4000 mg Infuse over 20 to 40 minutes at a rate not to exceed 100 mg/minute.

d) What is the volume that you need to draw after reconstitution in order to administer 500 mg IV Ampicillin?

e) You are advised that the Ampicillin dose will need to be administered as an IV additive via a syringe pump over 20 minutes by further diluting it in Normal Saline (NS). What is the total volume that you will need to dilute as per provided IV administration guidelines?

f) What is the rate per hour that you need to set on the Syringe pump if you want the volume of the diluted Ampicillin and an additional 4 ml of Normal Saline flush to be infused over 20 minutes?

ANSWER

Administering IV Ampicillin: Medication Calculation and Administration

Ampicillin is a commonly used antibiotic that requires careful dosing and administration to ensure patient safety and effectiveness. Let’s address the medication calculation and administration steps for the given scenario:

Lowest Safe Daily Dose

According to the formulary guidelines, the lowest safe daily dose for Ampicillin is 50 mg/kg/day. For a 20 kg patient:
Lowest dose = 50 mg/kg/day × 20 kg = 1000 mg/day

Highest Safe Daily Dose

The formulary states that the maximum daily dose of Ampicillin is 200 mg/kg/day. For a 20 kg patient:
Highest dose = 200 mg/kg/day × 20 kg = 4000 mg/day

Appropriate Order

The order reads 500 mg q6h (every 6 hours), and the patient’s weight-based dose range is between 1000 mg/day and 4000 mg/day. The ordered dose falls within this range, making it an appropriate order according to the formulary guidelines.

Volume after Reconstitution

The concentration of the reconstituted solution is 125 mg/mL. To administer 500 mg of Ampicillin, the required volume can be calculated using the formula:
Volume (mL) = Dose (mg) / Concentration (mg/mL)
Volume = 500 mg / 125 mg/mL = 4 mL

Dilution for IV Administration

To further dilute the Ampicillin for IV administration, it needs to be diluted to a concentration of 100 mg/mL or less. The total volume required can be calculated using the formula:
Total Volume (mL) = Dose (mg) / Concentration (mg/mL)
Total Volume = 500 mg / 100 mg/mL = 5 mL

Rate per Hour for Syringe Pump

The administration guideline suggests infusing the diluted Ampicillin and additional Normal Saline flush over 20 minutes. To calculate the rate per hour for the syringe pump, you can use the following formula:
Rate (mL/hr) = Total Volume (mL) / Time (hr)
Rate = 5 mL / (20 min / 60 min) = 15 mL/hr

In conclusion, Ampicillin administration involves careful calculation and adherence to formulary guidelines to ensure patient safety and therapeutic effectiveness. The ordered dose falls within the recommended dose range for the patient, and the dilution and administration rates align with established guidelines for safe and effective IV administration.