Drug Dosage Calculated by Body Weight
Order: Garamycin 8 mg / kg / 24 hr in 6 divided doses.
Weight: The patient weighs 165 pounds.
Label: Garamycin 40 mg / ml
Step 1: Is the weight in kilograms? If not, convert pounds to kilograms.
165 lbs = 75 kg
Step 2: What is the total 24 hr dose?
8 mg / kg
Set up the proportion and solve it.
8 mg : 1 kg :: x mg : 75 kg
x = 8 * 75
x = 600
The patient is to receive 600 mg / 24 hours
Step 4: How much will the patient receive in each dose?
Divide the total dose by the number of divided doses
600 / 6 = 100 mg per dose
The patient will receive Garamycin 100 mg IM 6 times a day (or q 4 hours)
Step 5: What will the nurse administer for each dose?
40 mg : 1 ml :: 100 mg : x ml
1 * 100 = 40 x
100 / 40 = x
2.5 = x
2.5 ml per dose
*** What will be the dose if the patient weighs 99 lbs? (Use the same order and label)
99 lb = 45 kg
8 mg * 45 kg = 360 mg / day
360 / 6 = 60 mg per dose (total = 6 doses, q 4 hours)
1.5 ml
Calculating a titrated IV Drip.
A Heparin drip is usually 500 ml D5W with 25,000 units heparin sulfate.
Order: Continuous IV Heparin @ 1200 units / hour.
Label: 500 ml D5W with 25,000 units Heparin Sulfate
The first ratio is the information from the label
25,000 units : 500 ml
The second ratio is the information from the order, including the unknown.
1,200 units : x ml
Set up the proportion and solve for x.
25,000 units : 500 ml :: 1,200 units : x ml
500 * 1,200 = 25,000 * x
600,000 = 25,000x
600,000 / 25,000 = x
600 / 25 = x
24 = x
24 ml
The heparin should be infused at 24 ml / hr
*** Using the same label, how many ml’s per hour would be correct for the order:
heparin drip at 1350 units per hour? ***
dicloxacillin sodium 125 mg po q6h
Child weighs 55 lb
Recommended dose 12.5 - 25 mg / kg / day in 4 divided doses
Dicloxacillin oral suspension 62.5 mg / 5 mL
Chloramphenicol 55 mg IV q 12h
8 day old infant weighing 2200 g
Recommended dose 25 - 50 mg / kg / day in 2 doses
Cefixime 120 mg po daily
Child weighs 33 lb
8 mg / kg once daily or 4 mg / kg q 12 hr
Cefixime suspension 100 mg per 5 mL in a 50 mL bottle.
tobramycin 8 mg IM q 6h Infant weighs 5000 g
Recommended dosage of tobramycin is 2 - 2.5 mg / kg q 8 h or 1.5 - 1.9 mg / kg q 6 h
80 mg / 2 mL
80 : 2 :: 10 : x
Digoxin 0.15 mg po q 12 h
9 year old child weighing 70 lb
Recommended pediatric dose is 7 - 10 mcg / kg / day in 2 divided doses