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.
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
How many mL in a tablespoon (T or tbs)?
15
How many mL in one ounce?
30
Convert 0.3 g to kg.
0.0003
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
Convert 2250 g to kg.
2.25 => 2.3
A child weighs 10 lb 2 oz. What is their weight in kg?
1. First, convert the 2 oz to lbs. 2 oz is 0.1 lbs. This gives you 10.1 lbs.
2. Now convert 10.1 lbs to kg.
3. Answer: 4.59 => 4.6 kg
Convert 8 lbs 4 oz to kg.
3.8 kg
You are caring for a patient at home who must take magnesium
hydroxide/aluminum hydroxide (Maalox) 30 mL PO. How many tbsp will you
instruct the patient to take?
2
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.
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
How many mL in a tablespoon (T or tbs)?
15
How many mL in one ounce?
30
Convert 0.3 g to kg.
0.0003
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
Convert 2250 g to kg.
2.25 => 2.3
A child weighs 10 lb 2 oz. What is their weight in kg?
1. First, convert the 2 oz to lbs. 2 oz is 0.1 lbs. This gives you 10.1 lbs.
2. Now convert 10.1 lbs to kg.
3. Answer: 4.59 => 4.6 kg
Convert 8 lbs 4 oz to kg.
3.8 kg
You are caring for a patient at home who must take magnesium
hydroxide/aluminum hydroxide (Maalox) 30 mL PO. How many tbsp will you
instruct the patient to take?
2
