Dosage Calculations Practice
Order: Biaxin 200 mg p.o. q 12 h for a child who weighs 45 lbs.
Have: Biaxin 125 mg per 5 mL
Biaxin label states 15 mg/kg/day in two equal doses.
Is this dosage safe?
1. Convert lbs to kgs. 45lbs = 20.5 kg
2. Calculate the recommended dose per day. A child weighing 20.5 kg can have 307.5
mg PER DAY. So, divide 307.5 by 2 to get a single dose. So, the maximum single dose
is 153.75 mg.
3. NO, the ordered dose is not safe. The doctor ordered 200 mg which is more than
153.75 mg.
How many mcg in a mg?
1000
Order: D5LR 1250 mL IV over 8 hours.
What is the infusion rate in mL/h?
Answer: 156 mL/h
Divide 1250 by 8
156.25 => 156
Order: Amoxil 200 mg q 8 h
Have: 50 mg/ml
Label: 20 to 40 mg/kg/day in divided doses every 8 hours.
The patient weighs 10 kg. Is this order safe?
1. First, calculate the minimum and maximum dose per day. The minimum amount
would be 200 mg. (20 x 10) The maximum amount would be 400 mg. (40 x 10)
2. Now, since the dose is given every 8 hours, divide the minimum and maximum by 3,
since 3 doses can be given in one day (24 hours). The minimum single dose is 66.7 mg,
and the maximum single dose is 133.3 mg.
3. NO, the ordered dose is not safe. The doctor ordered 200 mg for a single dose which
is more than the maximum allowed single dose of 133.3 mg.
How many mL in a teaspoon (tsp)?
5
How many grams are in a kilogram?
1000
How many teaspoons are in a tablespoon?
, 3
How many ounces are in a pound?
16
How many pounds are in a kilogram?
2.2
Convert 21.3 kg to lbs.
46.86
Tridil is infusing at 15 mL/hr on an infusion pump. The drug is mixed 50 mg in 500
mL DsW. How many mcg/min is the patient receiving?
Answer: 25 mcg/min
First, convert the 50 mg to mcg. 50 mg = 50,000 mcg
Now, how many mcg is in 1 mL?
50,000 mcg/500 mL = 100 mcg/mL
Now, how many mcg/hr is the pt receiving?
100 mcg x 15 mL = 1,500 mcg/hr
So, 1500 mcg/60 min = 25 mcg/min
How many mL in a tablespoon (T or tbs)?
15
How many mL in one ounce?
30
Convert 0.3 g to kg.
300
How many ounces in a cup?
8
How many mL in a cup?
240
Convert 22.2 kg to lbs.
48.84 lbs
Convert 89 kg to lbs.
195.8
Order: D5W IV at 125 mL/h
Drop factor: 10 gtt/mL
Calculate flow rate in gtt/min.
Answer: 21 gtt/min
(volume in mL/time in min) x drop factor
(125/60) x 10
2.08 x 10 = 20.8 => 21
Order: Biaxin 200 mg p.o. q 12 h for a child who weighs 45 lbs.
Have: Biaxin 125 mg per 5 mL
Biaxin label states 15 mg/kg/day in two equal doses.
Is this dosage safe?
1. Convert lbs to kgs. 45lbs = 20.5 kg
2. Calculate the recommended dose per day. A child weighing 20.5 kg can have 307.5
mg PER DAY. So, divide 307.5 by 2 to get a single dose. So, the maximum single dose
is 153.75 mg.
3. NO, the ordered dose is not safe. The doctor ordered 200 mg which is more than
153.75 mg.
How many mcg in a mg?
1000
Order: D5LR 1250 mL IV over 8 hours.
What is the infusion rate in mL/h?
Answer: 156 mL/h
Divide 1250 by 8
156.25 => 156
Order: Amoxil 200 mg q 8 h
Have: 50 mg/ml
Label: 20 to 40 mg/kg/day in divided doses every 8 hours.
The patient weighs 10 kg. Is this order safe?
1. First, calculate the minimum and maximum dose per day. The minimum amount
would be 200 mg. (20 x 10) The maximum amount would be 400 mg. (40 x 10)
2. Now, since the dose is given every 8 hours, divide the minimum and maximum by 3,
since 3 doses can be given in one day (24 hours). The minimum single dose is 66.7 mg,
and the maximum single dose is 133.3 mg.
3. NO, the ordered dose is not safe. The doctor ordered 200 mg for a single dose which
is more than the maximum allowed single dose of 133.3 mg.
How many mL in a teaspoon (tsp)?
5
How many grams are in a kilogram?
1000
How many teaspoons are in a tablespoon?
, 3
How many ounces are in a pound?
16
How many pounds are in a kilogram?
2.2
Convert 21.3 kg to lbs.
46.86
Tridil is infusing at 15 mL/hr on an infusion pump. The drug is mixed 50 mg in 500
mL DsW. How many mcg/min is the patient receiving?
Answer: 25 mcg/min
First, convert the 50 mg to mcg. 50 mg = 50,000 mcg
Now, how many mcg is in 1 mL?
50,000 mcg/500 mL = 100 mcg/mL
Now, how many mcg/hr is the pt receiving?
100 mcg x 15 mL = 1,500 mcg/hr
So, 1500 mcg/60 min = 25 mcg/min
How many mL in a tablespoon (T or tbs)?
15
How many mL in one ounce?
30
Convert 0.3 g to kg.
300
How many ounces in a cup?
8
How many mL in a cup?
240
Convert 22.2 kg to lbs.
48.84 lbs
Convert 89 kg to lbs.
195.8
Order: D5W IV at 125 mL/h
Drop factor: 10 gtt/mL
Calculate flow rate in gtt/min.
Answer: 21 gtt/min
(volume in mL/time in min) x drop factor
(125/60) x 10
2.08 x 10 = 20.8 => 21
