PTCB Order Entry 5/6

If a patient is taking 0.5 g of cephalexin monohydrate t.i.d., the daily dose, in mg, is:

• 500

• 1000

• 1500

• 2000

Answer explanation

First, determine how much cephalexin monohydrate is required per day by multiplying the amount per dose by the number of doses per day. The abbreviation "t.i.d." (from the Latin ter in die) means three times day.

0.5 g/dose x 3 doses/day = 1.5 g/day

Then, because the question asks for the total daily dose in mg, convert g to mg by moving the decimal point three places to the right or multiplying by 1000:

1.5 g/day x 1000 mg/g = 1500 mg/day

How many 8 mg tablets will the technician need to prepare ondansetron oral liquid with a concentration of 0.8 mg/mL and final volume of 100 mL?

• 1

• 4

• 8

• 10

Answer explanation

The first step in solving this problem is to calculate how many mg of ondansetron are needed for this prescription. The concentration needed is 0.8 mg/mL and we need a total of 100 mL. This can be done by multiplication.

0.8 mg/mL × 100 mL = 80 mg

You know now that you need 80 mg total and have 8 mg tablets available to you. To calculate out how many tablets you need, you can use division.

80 mg ÷ 8 mg/tablet = 10 tablets

What volumes of 40% iodine solution and 90% iodine solution must be combined to make 1500 mL of a 50% solution?

• 20 mL of 90% solution and 1480 mL of 40% solution

• 300 mL of 90% solution and 1200 mL of 40% solution

• 1200 mL of 90% solution and 300 mL of 40% solution

• 1480 mL of 90% solution and 20 mL of 40% solution

Answer explanation

The first step in solving this problem is to use the alligation method to find out how many parts of the 90% and 40% iodine solution are needed.

90% 10 parts of 90% iodine solution
50%
40% 40 parts of 40% iodine solution

You set up the above calculation by putting the highest concentration on the top (90%), the lowest concentration on the bottom (40%) and your desired concentration in the middle (50%). You then subtract the desired concentration from the higher concentration to find out how many parts of the lower concentration that you need (90% - 50% = 40 parts of 40% iodine solution). Then, you subtract the lower concentration from the desired concentration to find out how many parts of the higher concentration that you need (50% - 40% = 10 parts of 90% iodine solution).

From those calculations, you can determine that there are 50 total parts (10 parts + 40 parts) in the entire 1500 mL of solution. You then can use proportions to calculate how many mL of each of the solutions you will need to measure out to obtain a 50% concentration.

(50 parts/1500 mL) = (10 parts/x mL) x = 300 mL of 90% iodine solution
(50 parts/1500 mL) = (40 parts/x mL) x = 1200 mL of 40% iodine solution

What amount of a drug, in mL, is required to prepare 2 pints of a 1:1300 solution?

• 0.73

• 1.374

• 728

• 1374

Answer explanation

In order to solve this question, you first need to understand conversions. One pint is equal to 473 mL, so two pints is equal to 946 mL (473 mL × 2 = 946 mL). The next step is to understand what the ratio strength is telling you. If you need to make a 1:1300 solution, then that means that there is 1 mL of drug in 1300 mL of solution. Using that information, you can calculate how much drug you need to make 946 mL of solution by setting up a proportion and solving for x.

(1 mL/1300 mL) = (x mL/946 mL) x = 0.73 mL

Which of the following is an example of a medication in unit-of-use packaging?

• Lidocaine viscous 2%, 120 mL bottle

• Nystatin powder, 30 g bottle

• Heparin 100 units/mL, 1 mL vial

• Hydrocortisone 2.5% ointment, 30 g tube

Answer explanation

A unit-of-use package is a container/closure system designated to hold a specific quantity of a drug product for a specific use and intended to be used or dispensed to a patient without any modification except for the addition of appropriate labeling, according to the American Society of Health-System Pharmacists (ASHP). This typically excludes packages that contain multiple doses.

A cefaclor suspension label states, "Add 80 mL of water to yield 100 mL of 250 mg/5 mL." How much total water, in mL, is needed to yield 200 mL of 125 mg/5 mL?

• 80

• 100

• 180

• 200

Answer explanation

The first step to answer this question is to calculate how many mg of cefaclor will be contained in the 100 mL bottle that has a strength of 250 mg/5 mL. This can be done by setting up a proportion and solving for x:

(250 mg/5 mL) = (x mg/100 mL) x = 5000 mg cefaclor

The next step is to confirm that 200 mL of 125 mg/5 mL contains the same amount of drug. This can be done by setting up a ratio and proportion and solving for x:

(125 mg/5 mL) = (x mg/200 mL) x = 5000 mg cefaclor

Since the amount of drug product is the same, we need to find the powder volume of the suspension in the 250 mg/5 mL concentration. In this case, 80 mL of water is added to the powder volume to yield a total volume of 100 mL. This can be set up as an equation, solving for x:

80 mL water volume + x mL powder volume = 100 mL total volume x = 20 mL powder volume

To reach a total volume of 200 mL using the same amount of drug (same amount of powder volume), the amount of water can be set up in an equation, solving for x:

x mL water volume + 20 mL powder volume = 200 mL total volume x = 180 mL water volume added

What volume, in mL, of Humulin R U-100 insulin is necessary to withdraw 28 units?

• 0.028

• 0.28

• 2.8

• 28

Answer explanation

In order to solve this problem, you need to understand that U-100 insulin means that there are 100 units of insulin in 1 mL. Using this conversion figure, we can determine the number of mL required for 28 units of insulin by setting up a proportion and solving for x.

(100 units/mL) = (28 units/x mL) x = 0.28 mL

A patient whose body surface area is 1.78 m2 is to receive 5-fluorouracil 650 mg/m2/day for 5 days. What is the total amount of medication, in g, this patient should receive during this course of therapy?

• 1.157

• 5.785

• 1157

• 5785

Answer explanation

To calculate the correct dose of 5-fluorouracil, you need to take the dosage and multiply it by the patient's BSA.

650 mg/m2 × 1.78 m2 = 1157 mg

This figure should be converted to grams, and then multiplied by the number of days in the course of therapy.

1157 mg/day x 1 g/1000 mg x 5 days = 5.785 g

A prescription for a child calls for amoxicillin suspension 150 mg q8h. The available amoxicillin suspension is 250 mg/5 mL. What volume, in mL, should the child receive daily?

• 2.4

• 3

• 9

• 24

Answer explanation

In order to answer this question, you first need to understand the abbreviations. The abbreviation "q8h" means every 8 hours, or three times a day, so the child is supposed to receive 150 mg three times a day. If you have 250 mg/5 mL available, you can set up a proportion to calculate how many mL are needed per dose.

(250 mg/5 mL) = (150 mg/x mL) x = 3 mL

The child will need to receive 3 mL three times a day, so you can multiply the 3 mL dose by 3 to obtain your total daily dose.

3 mL/dose × 3 doses/day = 9 mL per day

How many rifampin 300 mg capsules are required to make a 240 mL stock solution of rifampin syrup 10 mg/mL?

• 8

• 10

• 12

• 30

Answer explanation

To start this problem, you first need to find the total amount of rifampin required to make 240 mL of stock solution. Given that the final concentration will be 10mg/mL, we can calculate the total as follows:

240 mL x 10 mg/mL = 2400 mg

Now we can divide the total amount of rifampin needed by the number of mg per capsule:

2400 mg ÷ 300 mg/capsule = 8 capsules