Dosage Calculations Practice

You need to administer 250 mg of erythromycin (Erythrocin) PO. You have on hand 0.5 g tablets. How many tablet(s) will you give?

0.5

How many ounces in a cup?

8

Your patient has a Heparin drip running at 24 mL/hr. The Heparin bag reads 12,500 units/250 mL. How many units per hour is the patient receiving?

Answer: 1200 units/hr There is more than one way to solve this. This is the way easiest for me to understand. First, I want to figure out how many units are in 1 mL. Simply divide 12,500 by 250 to get 50 units/mL. We are administering 24 mL/hr. We know each mL has 50 units, so multiply 24 by 50 to get 1200 units/hr.

Order: Ancef 2 gm IVPB in 100 mL D5W in 45 minutes What is the infusion rate?

Answer: 133 mL/h (100/45) x 60 = 133.3 => 133

1/4 gr. = _____ mg

Answer: 15 Convert 1/4 to a decimal => 0.25, then solve

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: Armour Thyroid gr. X by mouth daily Supply: 300 mg tablets How many tablets will you administer per dose?

Answer: 2 Convert the grains to mg. gr. X means 10 grains. Since 1 grain = 60 mg, 10 grains = 600 mg, so you need 2 tablets.

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

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

What is the BMI for Mr. Jones weighing 210 lbs with a height of 6 feet, 3 inches?

Answer: 26.3 kg/m2 Convert lbs to kg. 220 lbs = 95.45 kg Convert height to meters. 6'3" = 75 inches 75" = 190.5 cm 190.5 cm = 1.905 meters Square the height...1.905 meters x 1.905 meters is 3.63 BMI is calculated by dividing the weight in kg by the height in meters squared. 95.45/3.63 = 26.3

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.

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.

Know how to read labels. Info on label: NDC 0009-0856-05 1mL Hemabate (large purple type) carboprost tromethamine (small purple type) Injection, USP Equivalent to 250 mcg carboprost INTRAMUSCULAR USE ONLY (purple type) Refrigerate at 2 degrees to 8 degrees celcius What is the trade name, generic name, dosage strength, total volume, directions for use, and storage instructions? Look up labels online and practice!

Trade name: Hemabate Generic name: carboprost tromethamine Dosage strength: 250 mcg per mL Total volume: 1 mL Directions for use: intramuscular use only Storage instructions: refrigerate at 2 degrees to 8 degrees celcius

Convert 0.625 to a fraction.

Write down 0.625 over 1. (0.625/1) Multiply the top and bottom by 1000. You are multiplying by 1000 because there are 3 digits after the decimal. If there were only 1 digit, you would multiply by 10. If there were 2 digits, you would multiply by 100. 4 digits would be 10000 and so on. After multiplying top and bottom by 1000, you will have 625 over 1000. Now, simplify this by dividing each by 125 (largest number that will go into each evenly). Now, you have 5 over 8, so 0.625 has been converted into the fraction 5/8. Note: If you're not sure what the largest number is that will go into each, just start with the one you know. In this instance you could start with 5 or 25. Just keep reducing until you can no longer divide each one with the same number and still get a whole number.

Convert 0.75 to a fraction.

Write down 0.75 divided by 1. (0.75/1) Multiply the top and bottom by 100. You are multiplying by 100 because there are 2 digits after the decimal. If there were only 1 digit, you would multiply by 10. If there were 3 digits, you would multiply by 1000. 4 digits would be 10000 and so on. After multiplying top and bottom by 100, you will have 75 over 100. Now, simplify this by dividing each by 25 (largest number that will go into each evenly). Now, you have 3 over 4, so 0.75 has been converted into the fraction 3/4. Note: If you're not sure what the largest number is that will go into each, just start with the one you know. In this instance you could start with 5 or 25. Just keep reducing until you can no longer divide each one with the same number and still get a whole number.

1 grain = ___ mg

64.8 mg (60)

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: 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.

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

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

How many grams are in a kilogram?

1000

How many mcg in a mg?

1000

How would you write 1000 mg/1 g as a ratio?

1000 mg : 1 g

What is 0030 in regular time?

12:30 A.M.

1 gm = _____ gr.

15

How many mL in a tablespoon (T or tbs)?

15

What is 3:00 P.M. in military time?

1500

How many ounces are in a pint?

16

How many ounces are in a pound?

16

Convert 89 kg to lbs.

195.8

How many pints are in a quart?

2

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

How many pounds are in a kilogram?

2.2

Convert 2250 g to kg.

2.25 => 2.3

How many mL in a cup?

240

How many teaspoons are in a tablespoon?

3

Convert 8 lbs 4 oz to kg.

3.8 kg

2 gm = _____ gr.

30

How many mL in one ounce?

30

Convert 0.3 g to kg.

300

1 Dram = _____ mL

4

Convert 21.3 kg to lbs.

46.86

Convert 22.2 kg to lbs.

48.84 lbs

How many mL in a teaspoon (tsp)?

5

The patient's output is 2025 mL during your 12-hour shift. If the patient had an intake of 3394 mL, what should you monitor the patient for as the nurse? A. Fluid volume overload B. Dehydration C. These findings are within normal limits. Continue to monitor.

A

Order: Diazepam 5 mg IV for q 6 h for agitation as needed Supply: gr. iss/2mL (the ss has a line over the top) How many mL will you administer per dose?

Answer: 0.1 mL iss(line over the ss) are Roman numerals. i = 1 and ss with a line over them means 1/2 or 0.5. So, if you see iss, it means 1 1/2 or 1.5. So, the supply is 1.5 grains per 2 mL. First, convert the 5 mg to gr. So, 5 mg = 0.08 gr. Set up your equation. I set up my equations by putting what I NEED = to what I am SUPPLIED. x(mL needed) over 0.08 gr. = 2 mL over 1.5 gr. Solve for x by cross multiplying.

Order: liquid suspension Aspirin 180 mg p.o. daily Supply: gr. V per 2 mL How many mL will you administer per dose?

Answer: 1.2 mL First, convert 180 mg to gr. So, 180 mg = 3 gr. Set up your equation. I set up my equations by putting what I NEED = to what I am SUPPLIED x (mL needed) over 3 gr. = 2 mL over 5 gr Solve for x by cross multiplying.

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

Mr. Smith weighs 95.45 kg and is 5 feet 4 inches tall. What is his BSA?

Answer: 2.07 m2 Convert the height to cm. 5'4" => 162.56 cm To calculate BSA, multiply the height in cm by the weight in kg. Divide that by 3600. Then, take the square root of that.

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

The MD orders your patient to start an IV Heparin drip at 18 units/kg/hr and to administer a loading bolus dose of 30 units/kg IV before initiation of the drip. You're supplied with a Heparin bag that reads 25,000 units/500 mL. The patient weighs 172 lbs. What is the flow rate you will set the IV pump at (mL/hr) and the amount of units for the IV bolus?

Answer: 28 mL/h, Bolus: 2346 units First, convert 172 lbs to kg. 172 lbs = 78.2 kg The doctor wants 18 units per kg. So, multiply 78.2 by 18 to get 1407.6 units. Set up your equation. I set up my equations by putting what I NEED = to what I am SUPPLIED. x (mL needed) over 1407.6 mg = 500 mL over 25000 units Solve for x by cross multiplying. For the bolus, you will multiply 30 by 78.2 and get 2346.

Your patient has a Heparin drip running at 29 mL/hr. The Heparin bag reads 10,000 units/ 100 mL. How many units per hour is the patient receiving?

Answer: 2900 units/hr There is more than one way to solve this. This is the way easiest for me to understand. First, I want to figure out how many units are in 1 mL. Simply divide 10000 by 100 to get 100 units/mL. We are administering 29 mL/hr. We know each mL has 100 units, so multiply 29 by 100 to get 2900 units/hr.

Order: Tylenol 1 gm by mouth q 6 h as needed for pain Supply: 5 gr. capsules How many capsules will you give?

Answer: 3 Convert 1 gm to grains. 1 gm = 15 grains. So, you need 3 of the 5 gr. capsules to make 15 gr.

Order: Morphine 1/8 grains IV q 4 h p.r.n. for pain Supply: 2 mg/mL How many mL will you administer per dose?

Answer: 3.75 First, convert 1/8 to a decimal. 1/8 grain = 0.125 grain. Now convert grains to mg. 0.125 grain = 7.5 mg. Set up your equation. I set up my equations by putting what I NEED = to what I am SUPPLIED. x (mL needed) over 7.5 mg = 1 mL over 2 mg Solve for x by cross multiplying.

Convert 0.3 g to mg.

Answer: 300 mg Since milli means 1000, just move the decimal 3 spots to the right. Or, set up an equation as follows: We know 1 g = 1000 mg. 1 g/1000 mg = 0.3 g/x Solve for x by cross mulitiplying.

Convert 3 L to mL.

Answer: 3000 mL Since milli means 1000, just move the decimal 3 spots to the right. Or, set up an equation as follows: We know 1 L = 1000 mL. 1 L/1000 mL = 3 L/x Solve for x by cross multiplying.

One liter NS to infuse over 24 hours using a microdrip (gravity flow). Calculate the flow rate in gtt/min.

Answer: 42 gtt/min Microdrip means 60 gtt 1 liter = 1000 mL (1000/1440) x 60 = 41.66

How many mL in a pint?

Answer: 480 (500) 16 oz x 30 mL = 480, but study materials say 500

gr. X = _____ mg

Answer: 600 mg In this problem, X represents the roman numeral 10. So, the question is asking how many mg in 10 grains. 1 grain = 60 mg, so 10 grains = 600 mg

Your shift is from 7a-7p. The patient had the following intake and output during your shift. Based on your calculation, the patient is at risk for? 0800: 8 oz orange juice, 6 oz yogurt, slice of bread, 10 cc flush 1000: 8 oz coffee w/ 1 oz of cream 1200: 12 oz soda, Two 12 oz cherry popsicles, 3 oz chocolate pudding, 4 oz chicken broth 1300: 6 oz soda, 12 oz custard 1600: 8 oz ice chips 1400-1900: 50 cc/hr IV infusion 0700: 500 cc urine 1100: emesis 100 cc, ileostomy stool 350 cc 1200: wound vac drainage 200 cc 1300: 250 cc urine 1500: JP drain 400 cc 1700: 350 cc urine 1730: 400 cc urine 1800: 350 cc urine 1830: ileostomy stool 400 cc 1845: 500 cc urine A. Intake: 2080 mL & Output: 3520 mL; monitor the patient for dehydration B. Intake: 2270 mL & Output: 3800 mL; monitor the patient for dehydration C. Intake: 3890 mL & Output: 2200; monitor the patient for fluid volume overload D. Intake: 4005 mL & Output: 2270 mL; monitor the patient for fluid volume overload

Answer: B Do not count solids like yogurt, bread, pudding, or custard. Intake and output is measured in mL. Convert ounces to mL. 1 oz = 30 mL Stool from an ileostomy is usually mostly liquid. Count it as output.

Your patient's recent PTT is 42. According to protocol, you need to increase the Heparin drip by 2 units/kg/hr and administer 30 units/kg IV bolus. You will recheck the PTT in 6 hours. The patient is currently receiving a Heparin drip at 16 units/kg/hr from a bag that reads 25,000 units/250 mL. The patient weighs 163 lbs. How many units will the patient receive as a bolus, and what will you change the flow rate to (mL/hr)?

Answer: bolus is 2,223 units, new flow rate 18 units/hr Convert 163 lbs to kg => 74.1 kg To calculate the bolus, multipy 74.1 by 30 => 2,223 units

Your patient's recent PTT is 45. According to protocol, you need to increase the Heparin drip by 2 units/kg/hr and administer 30 units/kg IV bolus. You will recheck the PTT in 6 hours. The patient is currently receiving a Heparin drip at 22 units/kg/hr from a bag that reads 25,000 units/250 mL. The patient weighs 129 lbs. How many units will the patient receive as a bolus, and how many units per kilogram per hour will the patient receive based on the new PTT result?

Answer: bolus will be 1758 units, increase drip to 24 units/kg/h Convert 129 lbs to kg => 58.6 kg To calculate the bolus, multiply 58.6 by 30 to get 1758

Calculate the patient's total urinary output for the shift. The patient has continuous bladder irrigation and a Foley catheter. 0800-1000: 3 Liters of bladder irrigation 1000: emptied Foley catheter 3600 mL 1100: 1 Liter of bladder irrigation 1200: 2 Liters of bladder irrigation and emptied 3250 mL from Foley catheter 1300: 1 Liter of bladder irrigation 1400: 1 Liter of bladder irrigation 1500: 1 Liter of bladder irrigation and emptied 3120 mL from Foley Catheter 1600-1900: 3 Liters of bladder irrigation 1900: emptied 4200 mL from Foley catheter

Intake: 2170 mL Remember, irrigation in NOT urine. You can not count it. The patient received 3000 mL of irrigation from 0800-1000. When the Foley cath was emptied at 10, there was a total of 3600 mL. 3000 mL of that was irrigation fluid. Only 600 mL was urine and considered output.

During your 12-hour shift from 7p - 7a, what is your patient's INTAKE and OUTPUT? 2000-0600: Jevity 50 mL/hr 0615: 50 cc free water flush 2100-0215: Two 250 mL of red blood cells 0115: 20 cc saline flush IV 0300: Zosyn IV 50 mL 0400: 10 cc saline flush IV Continuous Fluids: Heparin 10 mL/hr Normal Saline 100 mL/hr Ileostomy: 300 mL NG suction: 50 cc Urine: 1850 mL Wound vac: 100 cc

Intake: 2450 mL Output: 2300 mL Remember that 1 cc = 1 mL Notice that the Jevity is running at 50 mL/h for 10 hours, so that is a total of 500 mL. Continuous fluids are constant and run your entire shift.

Calculate the patients INTAKE during your 12-hour shift. 0800: Two pieces of toast, 2 cups of oatmeal, 8 oz yogurt, 12 oz orange juice, 2 oz grits 1000: Two 8 oz of coffee w/ 2 oz of cream in each 1100: 24 oz of ice chips 1200: IV infusion of Zosyn 50 mL, 2 mL IV push Zofran and 10 cc saline IV flush 1230: house salad, 12 oz soda, three 12 oz popsicles 1400: One pack of red blood cells (250 mL) 1500: 2 mL Morphine and 10 cc saline flush IV 1715: 10 cc saline flush IV 1600-1900: Normal Saline IV 100 cc/hr

Intake: 3394 mL Remember, intake is measured in mL. Convert all ounces to mL. 1 oz = 30 mL Also, ice melts to ONE HALF the total ounces. So, 24 ounces of ice melts to 12 ounces. Do NOT count solids like the toast, oatmeal, yogurt, grits, or salad. It has to be liquid at room temp to be counted.