Dosage Calculations Practice

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 A patient has a bottle of warfarin (Coumadin) 5 mg tablets at home. After his most recent international normalized ratio (INR), the doctor calls and tells him to take 7.5 mg/day. How many tablets (scored) should the patient take? 1.5 If your IV bag says 5% dextrose solution, what does the 5% represent? There are 5 g of dextrose per 100 ml in the bag. Order: NS 0.9% 250 mL IV over the next 4 hours How many mL per hour will you infuse? Answer: 63 mL/h 250 mL divided by 4 is 62.5. Round to the nearest whole number. Order: Ampicillin 500 mg IV in 50 mL in D5 1/2NS in 30 minutes. What is the infusion rate in mL/h? Answer: 100 mL/h Divide total mL by total minutes, then multiply by 60. (total mL ordered/total minutes) x 60 minutes (50 mL/30 min) x 60min 1.67 x 60 = 100.2 => 100 mL/h OR Convert 30 min to hours. 30 min = 0.5 hours 50 mL/0.5 = 100 mL/h Order: Ancef 2 gm IVPB in 100 mL D5W in 45 minutes What is the infusion rate in mL/h? Answer: 133 mL/h (100/45) x 60 = 133.3 => 133 You have an IVPB of ranitidine (Zantac) 50 mg in 50 mL D5W to run over 30 minutes. The tubing has a drip factor of 15. How many drops per minute will you set on the IV infusion controller? Answer: 25 gtt/min (volume in mL/time in min) x drip factor (50/30) x 15 1.67 x 15 = 25.05 => 25