PTCB Order Entry 1/6

Amoxicillin is ordered at 40 mg/kg/day in 3 divided doses for a 15 lb infant. If the stock solution is amoxicillin 125 mg/5 mL, what volume, in mL, should be administered per dose?

• 1.5

• 3.6

• 4.0

• 10.8

Answer explanation

The first step to solving this problem is to convert 15 lb to kg using the conversion 2.2 lb = 1 kg:

(2.2 lb/1 kg) = (15 lb/x kg) x = 6.8 kg

Next, multiply the mg/kg/day by the patient's weight in kg:

40 mg/kg/day x 6.8 kg = 272 mg/day

Then, divide by three to find how many mg are needed per dose:

272 mg/day ÷ 3 doses/day = 90.67 mg/dose, which rounds up to 91 mg/dose

Last, set up a proportion to determine how many mL should be administered per dose:

(125 mg/5 mL) = (91 mg/x mL)

x = 3.63 mL, which rounds down to 3.6 mL

If there are approximately 20 drops per mL in an eye solution, how long, in days, will 10 mL last if given 2 gtts OS b.i.d.?

• 25

• 30

• 50

• 60

Answer explanation

In order to solve this problem, you need to understand the abbreviations. The abbreviation “gtts” means drops, “OS” means left eye, and “b.i.d.” means two times per day. The patient is to use 2 drops into the left eye two times per day, so they will use 4 drops total per day (2 drops/dose × 2 dose/day = 4 drops/day). Next, you need to determine how many drops are contained in the bottle. Since the patient is receiving a 10 mL bottle of the eye drop solution and there are 20 drops in every mL, this can be done by multiplication (10 mL × 20 drops/mL = 200 drops). Finally, since you know how many drops are in the vial, you can calculate how many days the bottle will last with the patient using 4 drops/day using division.

200 drops ÷ 4 drops/day = 50 days

A medication suspension is compounded with 30 mL of cherry syrup and 140 mL each of nystatin, Maalox, and 2% viscous lidocaine. The patient is to swish and swallow one teaspoonful before meals 3 times a day. If the patient takes as directed, how many days should this compound last?

• 10

• 15

• 25

• 30

Answer explanation

You first need to calculate the total volume of the compound. By adding up the quantities of all of the compound ingredients you end up with 450 mL.

30 mL of cherry syrup + 140 mL nystatin + 140 mL Maalox + 140 mL 2% viscous lidocaine = 450 mL total

Next, you need to find out the total volume that the patient would take on a daily basis if they use 1 teaspoonful before meals 3 times a day. 1 teaspoonful is equal to 5 mL, so if they took the compound 3 times a day they would use 15 mL/day. By dividing the total amount that we start with by how much the patient would use per day, you will end up with the correct days supply.

450 mL ÷ 15 mL/day = 30 days

How much Mylanta, in mL, should be dispensed for the following prescription? Mylanta 1 oz q.i.d. (a.c. and h.s.) x 7 days

• 210

• 420

• 660

• 840

Answer explanation

In order to solve this problem, you need to understand the abbreviations. The abbreviation “q.i.d.” means four times a day, “a.c.” means before meals, and “h.s.” means at bedtime. The patient is to take 1 oz four times a day before meals and at bedtime for 7 days (the information before meals and at bedtime is extra information and is not needed to solve this problem). Next, you need to understand conversions. Since the problem is asking for an answer in mL, you need to convert oz to mL using the conversion 1 oz = 30 mL. Now you can calculate how many mL of Mylanta should be dispensed for the prescription using multiplication.

30 mL/dose × 4 doses/day × 7 days = 840 mL

A prescription order reads: Potassium chloride 10% (40 mEq/30 mL)

Dispense: 240 mL Sig: 1 tsp t.i.d.

How many mEq of KCl are to be taken daily?

• 10

• 20

• 30

• 45

Answer explanation

In order to answer this question, you must first understand the abbreviations. The abbreviation "t.i.d." means three times a day, so the patient is supposed to take 1 teaspoon three times a day. Next, you need to understand conversions. The concentration of the drug is given as 40 mEq/30 mL, so in order to determine how many mEq of KCl are to be taken daily, you need to convert the total teaspoons the patient is to take in a day to mL. This can be done by using the conversion 1 tsp = 5 mL (3 tsp × 5 mL/tsp = 15 mL).

The patient is taking 15 mL daily of the KCl. Next, you must calculate how many mEq of KCl are in 15 mL of the drug. This is done by setting up a proportion using the concentration of the drug you are given: 40 mEq/30 mL.

(40 mEq/30 mL) = (x mEq/15 mL) x = 20 mEq

A patient who weighs 110 lb requires an infusion of phenytoin at 5 mg/kg/dose t.i.d.

How much phenytoin, in mg, should the patient receive daily?

• 250

• 675

• 750

• 1650

Answer explanation

The first step to answering this question is to determine how much phenytoin the patient needs to receive per dose, since the given information is 5 mg/kg/dose. The patient’s weight is given in lb, which should be converted to kg using the conversion of 2.2 lb = 1 kg (110 lb ÷ 2.2 lb/kg = 50 kg). Now you can determine how much phenytoin the patient needs per dose by multiplying their weight and how much phenytoin they need.

(50 kg)(5 mg/kg/dose) = 250 mg/dose

Next, you need to understand abbreviations. The abbreviation “t.i.d.” means three times a day, so the patient will receive 3 doses of phenytoin per day. The total amount can be determined using multiplication.

(250 mg/dose)(3 doses/day) = 750 mg/day

How many fentanyl transdermal patches should be dispensed to a patient who is applying one patch every 72 hours for 2 weeks?

• 2

• 4

• 5

• 14

Answer explanation

This patient will be using 1 patch every 3 days (every 72 hours) for 14 days (2 weeks). You would calculate the number of patches needed by dividing the number of days that the medication is needed by how often the patient will be applying the patch.

14 days ÷ 3 days/patch = 4.7 patches

This number would be rounded up to 5 patches to have the patient get through their entire therapy regimen. The first 4 patches would get them through the first 12 days of therapy, and 1 additional patch would be needed for the last 2 days.

The usual dose of pyrantel pamoate suspension for the treatment of pinworms is 11 mg/kg of body weight.

How many mg of pyrantel pamoate should be given to a child weighing 88 lb?

• 110

• 220

• 330

• 440

Answer explanation

Option (D) is correct and can be calculated as follows.

First, convert the patient's weight from lb to kg using the conversion 2.2 lb = 1 kg:

(88 lb/x kg) = (2.2 lb/1 kg)
88 lb/2.2 lb = x kg
x = 40 kg

Next, determine the dose the patient needs by multiplying their weight by the recommended dose:

40 kg x 11 mg/kg = 440 mg

How many 0.75 mg dexamethasone tablets are needed to administer a 3 mg dose?

• 2

• 3

• 4

• 5

Answer explanation

This problem can be solved using division. Since 3 mg is needed for the dose, you need to determine how many 0.75 mg tablets will deliver 3 mg.

3 mg ÷ 0.75 mg/tablet = 4 tablets

A prescription is written for 1 drop of a specified sodium fluoride solution daily;

a volume of 24 mL is dispensed.

If 1 mL of the solution provides 15 drops, for how many days will the patient's supply last?

• 24

• 30

• 36

• 360

Answer explanation

The first step to solving this problem is to determine how many total drops are in the 24 mL bottle of fluoride solution. Since there are 15 drops in every mL, this can be done by multiplication (24 mL × 15 drops/mL = 360 drops). The patient is going to take 1 drop per day, and, since you know how many drops are in the bottle, you can calculate how many days the bottle should last using division.

360 drops ÷ 1 drops/day = 360 days