For many students, pharmacy math is one of the most feared parts of the PTCB exam. There is a lot of ground to cover and getting your ahead around the many types of questions can prove difficult. Here, we have put together some core math questions for the PTCB exam that you need to know.
As the adage goes, practice makes perfect. You need to practice as many sample math questions for the PTCB exam. The more questions you practice, the more gaps in your knowledge filled.
At first, math is difficult. With practice, it becomes effortless.
Here, we have put together a range of four PTCB math questions – some easy, some not so easy. Attempt each question first before reading our prepared answers. That way, you can identify where you may have gone wrong.
If you simply read the explained answers first, you will lose this golden learning opportunity.
A patient must be administered an IV infusion of a medicine over the course of 7 hours. If the total volume of the infusion is 0.8L, what is the infusion rate in mL/min?
First, always identify units.
In this question, we have competing units. On the one hand, it details hours and liters, but the question asks us to deliver the answer in milliliters and minutes. This means that we need to convert between units.
In this case:
Now that we have resolved the issue of units, we can proceed to answer the question.
800mL is the total infusion, which is infused intravenously into the patient over a 420-minute period.
Therefore, 800mL/420 minutes = 1.9mL/min
You may ask, why isn’t it 420 minutes / 800mL?
Think about the order of units. The question asks us for mL/min. Therefore, the mL must be the numerator (top value in a fraction) and min must be the denominator (bottom value in a fraction).
Answer: 1.9mL per minute is infused into the patient over a 7-hour period.
At the end of the 7-hour period, all 800mL will have been administered.
How much hydrocortisone powder is needed to compound 80 g of hydrocortisone cream at 1% concentration?
Concentrations are routinely asked on the PTCB test.
In this case, we are talking about solids and semisolids – powers/creams etc.
A 1% concentration = 1 gram of active ingredient in 100 grams of medicine.
In this case, we have 80 grams of creams. The question asks us to find out how much of that 80 grams is hydrocortisone powder. After all, creams are not just made from active ingredients (the drug). They are also formulated with non-active ingredients such as diluents, vehicles, and preservatives, to name a few.
Therefore, in this case, 1% of 80 grams = 0.8 grams
The other 99.2% are non-active ingredients.
Answer: 0.8 grams of hydrocortisone powder is needed to produce 80 grams of hydrocortisone cream at a concentration of 1%.
How many mL of 60% alcohol should be mixed with 30% alcohol to prepare 50 mL of 50% alcohol?
At first, these kinds of question can seem difficult. It may be challenging to get your ahead around exactly what is going on.
Let’s try and break this one down into its component parts.
We have two solutions of differing concentrations:
The question is asking us to mix these solutions together to produce 50mL of 50% concentration. In other words, should we add 10mL of 60% solution with 40mL of 30% solution to produce 50mL of solution? Are these the correct quantities? That is the principle behind this question – to establish exactly how much of both solutions need to be mixed together.
One of the simplest ways to answer this question is to use the alligation method. Alligation math questions for the PTCB exam have become more common in recent years.
To use the method, you must work through the problem in the following format:
Now, we must:
The ratio is therefore 20:10.
20:10 is the same as 20 parts:10 parts
Total number of parts = 30 parts
(20 / 30) x 50mL = 33.3mL of 60% solution needed
(10 / 30) x 50mL = 16.7mL of 30% solution needed
Conclusion – when we add together 33.3mL of 60% solution and 16.7mL of 30% solution, it gives us a solution of 50mL with a concentration of 50%.
Alligation questions are routinely asked on the PTCB exam. It is important that you commit this method to memory to ensure that you are fully prepared for this style of question.
A pharmacy technician receives a prescription for carboplatin 50mg/m2 per dose. If the BSA of the patient is 1.4m2, how many milligrams of carboplatin are needed to satisfy the prescription?
Doses are not always determined based on whether the patient is an adult or a child. In some cases, the body surface area of the patient is needed to calculate the dose.
In this case, we are told that carboplatin – an anticancer drug – must be administered at a dose of 50 milligrams per every 1 meter squared of the body surface area (BSA) of the patient.
BSA of the patient = 1.4m2
Therefore: (1.4m2) x 50mg = 70 milligrams are needed
Intuitively, this makes sense. After all, if 50mg must be given for 1 meter squared, then clearly the dose of the medicine must be higher than 50mg for a patient who is 1.4 meters squared.
Answer: 70mg of carboplatin is needed for a patient whose BSA is 1.4m2
Studying pharmacy technician math doesn’t have to be difficult.
What matters is that you do not fall into the trap of memorizing methods for the sake of it. You need to understand the method of resolving each problem. That way, you can identify how to solve a similar problem that is not the same as what you originally learned. If you find yourself memorizing methods for the sake of it, you will find it very difficult to adapt to new problems, even if they look similar to the questions you practiced up to this point.
Above, we broke each question down into its component parts – explaining the thought process behind each question and answer. This is the kind of preparation that you – the student – must apply to your own study. Initially, this will take time, particularly if math is not your thing. But do remember – that accuracy is particularly important in pharmacy. By learning math, you are learning how to be accurate with patient’s lives.
Therefore, do not treat this subject lightly.
Consider it an important branch of your career and one that helps to prevent medication errors that could damage the lives of patients.
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