NCLEX: Drug Dosage Calculation Exam 3

1. Your patient is taking acetaminophen (Tylenol) gr 15 every 6 hours PO for headache pain. You know the maximum safe dose is 4 g in 24 hours. Is the dose safe?

1. 2 g/day, safe!
2. 4 g/day, safe!
3. 6 g/day, not safe!
4. 8 g/day, not safe!

2. You are caring for your ill grandmother at home. She has an order for magnesium hydroxide/aluminum hydroxide (Maalox) 10 mL PO prn stomach upset. How do you instruct her to measure her dose using household measuring spoons?

1. 1 teaspoon
2. 1 1/2 teaspoons
3. 2 teaspoons
4. 2 1/2 teaspoons

3. Your patient needs 2,000 mL of saline IV over 4 hours for severely deficient fluid volume. How many milliliters per hour will you set on a controller?

1. 500 mL/hour
2. 250 mL/hour
3. 33 mL/hour
4. 8 mL/hour

4. Your patient needs 2,000 mL of D5W IV over 24 hours, to be delivered with a tubing set with a drop factor of 15. How many drops per minute will you set for an infusion rate?

1. 83 gtts/minute
2. 42 gtts/minute
3. 36 gtts/minute
4. 21 gtts/minute

5. You have on hand penicillin 300,000 units/mL. Your order reads penicillin 1,000,000 units IM. How will you fill the syringe?

1. 0.3 mL
2. 3.3 mL
3. 4.4 mL
4. 5.5 mL

6. The physician orders alprazolam (Xanax) 0.5 mg PO. You have on hand Xanax 0.25 mg tablets. How many will you give?

1. 1/2 tablet
2. 1 tablet
3. 1 1/2 tablets
4. 2 tablets

7. You need to administer 250 mg of erythromycin PO. You have on hand 0.5 g tablets. How many tablets will you give?

1. 1/2 tablet
2. 1 tablet
3. 1 1/2 tablets
4. 2 tablets

8. You need to administer 400 mg of erythromycin PO. You have on hand a suspension of 125 mg/5 mL. How much will you prepare?

1. 1.6 mL
2. 3.2 mL
3. 12 mL
4. 16 mL

9. You need to administer furosemide (Lasix) 2 mg/minute via continuous IV infusion on a controller. Pharmacy has sent a bag of Lasix 400 mg diluted in D5W 250 mL. How many milliliters per hour will you set on the controller?

1. 75 mL/hour
2. 100 mL/hour
3. 150 mL/hour
4. 250 mL/hour

10. A patient with HIV infection is receiving 200 mg of didanosine PO bid. The pharmacy only has powder packets with 167 mg each, to be mixed with 4 oz of water. How many packets should the patient mix? How much should the patient take? How can it be measured?

1. 4.8 oz
2. 3.3 oz
3. 2.2 oz
4. 1.8 oz

Answers and Rationales

1. Answer: B. (15 gr/dose) x (4 doses/day) x (1g/15 gr) = 4 g/day. *The dose is at the upper limit of a safe dose.
2. Answer: C. 10 mL x (1 tsp/5mL) = 2 teaspoons  
3. Answer: A. (2,000 mL/ 4 hours) = 500 mL/ hour
4. Answer: D.  (2,000 mL/24 hours) x (1 hour/60 minutes) x 15 gtts/mL = 21 gtts/minute
5. Answer: B.  1,000,000 units x (1 mL/ 300,000 units) = 3.3 mL
6. Answer: D.0.5 mg x (1 tablet/ 0.25 mg) = 2 tablets 
7. Answer: A. 250 mg x (1g/1,000mg) x (1 tablet/ 0.5 g) = 1/2 tablet
8. Answer: D.  400mg x (5 mL/125mg) = 16 mL
9. Answer: A.  (2mg/minute) x (250 mL/400 mg) x (60 minutes/ 1 hour)= 75 mL/hour
10. Answer: A. 200 mg x (4 oz / 167 mg) = 4.8 oz *The patient will have to mix two packets, each in 4 oz of water, and drink 4.8 oz measured in a calibrated measuring cup. If a cup that measures milliliters is available, then: 4.8 oz x (30 mL/1 oz)= 144 mL or  144 mL x (1 tbsp/15 mL)= 9.6 tbsp.