PharmacyTechnician Certification exam math questions

[lavenderhearts]

Hi everyone,

I am studying to take the Pharmacy technician certification exam by PTCB and I am having a hard time with the math questions because I don't know how to do them. I am hoping you all will help with understanding how to do the questions.

Here are the math questions...

1. A 500mL I.V. bag contains 2.5 grams of a drug. The administration set is calibrated to 16gtt/mL, and set to deliver 5gtt/min. What percentage concentration is the solution?
Answer: A. 0.5%

2. A patient was started on a drip of D10W from a 500mL at 1400. The micro-drip (60gtt/mL administration device was set to deliver 30gtt/min. If the patient is administered the entire bag, how much dextrose will they receive?
Answer: 50grams

3. A patient is receiving an infusion from a 500mL bag containing a 0.5% solution of drug S. The drop factor is calibrated at 12gtt/mL and the flow rate is set to 10gtt/min. If the infusion is to run for 4 hours, how much of the active drug will the patient receive?
Answer: 1000mg

I will really appreciate your help!!!

Thank you!!!!

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[y0ssarian87]

Hi everyone,

I am studying to take the Pharmacy technician certification exam by PTCB and I am having a hard time with the math questions because I don't know how to do them. I am hoping you all will help with understanding how to do the questions.

Here are the math questions...

1. A 500mL I.V. bag contains 2.5 grams of a drug. The administration set is calibrated to 16gtt/mL, and set to deliver 5gtt/min. What percentage concentration is the solution?
Answer: A. 0.5%

2. A patient was started on a drip of D10W from a 500mL at 1400. The micro-drip (60gtt/mL administration device was set to deliver 30gtt/min. If the patient is administered the entire bag, how much dextrose will they receive?
Answer: 50grams

3. A patient is receiving an infusion from a 500mL bag containing a 0.5% solution of drug S. The drop factor is calibrated at 12gtt/mL and the flow rate is set to 10gtt/min. If the infusion is to run for 4 hours, how much of the active drug will the patient receive?
Answer: 1000mg

I will really appreciate your help!!!

Thank you!!!!

These are extremely easy math problems, so I'm wondering if you're having trouble understanding certain terms.

1. This is simply amount of drug (in grams) divided by volume (in mL). Thus,

2.5g/500mL = 0.005 g/mL = 0.5% (w/v)

2. This is asking how much dextrose is in a 500mL bag of D10W (10% dextrose in water). Thus,

500 mL * 10% (w/v) = 50 g

3. This is the first problem where you use the info about the drops, because it's asking you how much the patient received over an amount of time.

4 hrs * (60 min/hr) * (10gtt/min) * (1 mL/12gtt) * 0.5% (w/v) = 200 mL * 0.5% = 1 g = 1000 mg

 

[y0ssarian87]

Let me know if there is a particular concept that you are having trouble with, and I'll try to provide an explanation for how to approach it.

 

[lavenderhearts]

Let me know if there is a particular concept that you are having trouble with, and I'll try to provide an explanation for how to approach it.

I'm having problems with understanding the concepts of the problem. I don't know what volume and solute they are talking about but I am studying to better understand it and thank you so much for your help. I am doing practice test and I can get most questions right except the math questions concerning volume, time, and grams to milligrams. Can you please help me understand those concepts.

 

[lavenderhearts]

I have another question that I can't figure out and here it is...

A custom compound suspension has been ordered for a patient to pick up. The active drug available in 300mg tablets and the order is asking for 200mL of a 1.5% solution. How many tablets will be used to compound this suspension?

 

[y0ssarian87]

I'm having problems with understanding the concepts of the problem. I don't know what volume and solute they are talking about but I am studying to better understand it and thank you so much for your help. I am doing practice test and I can get most questions right except the math questions concerning volume, time, and grams to milligrams. Can you please help me understand those concepts.

Did my explanations above help? If not, where did you get tripped up? For the very first problem you sent me, that was very basic. You've got a bag of fluid:

and there is 2.5 g of drug in the bag, dissolved in the 500 mL:

To calculate the percent strength of a solid dissolved in a liquid (w/v) there are a couple ways to think about it:

1) It can be thought of as grams of drug per 100 mL of solvent. So, if there are 2.5 grams in 500 mL, there are 0.5 g in 100 mL. Thus, 0.5%. This is the same as getting your answer in g/mL and multiplying by 100. For the sake of example, 2.5g/500mL is 0.005 g/mL, which is 0.5%.

2) You can also think about it this way: the amount of drug is small compared to the solvent (the 500 mL). If we're assuming this is an aqueous solvent, we have about 500 g of mass in the 500 mL, and the drug is 2.5 grams. 2.5g/500g = 0.005 = 0.5%

Ultimately percent strength (w/v) calculations assume the solute doesn't affect the final density much and that the solvent is aqueous (near 1 g/mL). This is why we get our answer to grams per milliliter.

 

[y0ssarian87]

I have another question that I can't figure out and here it is...

A custom compound suspension has been ordered for a patient to pick up. The active drug available in 300mg tablets and the order is asking for 200mL of a 1.5% solution. How many tablets will be used to compound this suspension?

I'm not going to answer math questions for you, but I'll help you work it out.

1) How much active drug in grams is in 100 mL of the final solution?

2) So how much is in 200 mL?

3) How much is that in mg?

4) How many tablets do you need?

 

[lavenderhearts]

The answer is 4? I did 15grams/200mL which gave me .7 which is 700mg

 

[y0ssarian87]

The answer is 4? I did 15grams/200mL which gave me .7 which is 700mg

No, that is incorrect. If you have 100 mL of a 1.5% solution, how many grams of drug are in it?

 

[lavenderhearts]

1.5

 

[y0ssarian87]

1.5

Cool. So if there are 1.5 g in 100 mL, how many grams are in 200 mL?

How many mg is this? How many tabs?

 

[PharmDCandidate2014]

1.5

Good, 1.5 mg of drug in 100 mL solution. Set up a proportion and let 1.5 g / "x" g = 100 mL / 200 mL.

Solve for x, you get 3.0 grams in 200 mL solution. (We still have the equivalent of a 1.5% solution, but now in 200 mL instead of 100 mL)

Now that we have 3.0 grams, we need to convert this into milligrams. The conversion factor here is 1,000 mg/g.

So, 3.0 g = 3,000 mg.

If our active drug in question contains 300 mg / 1 tablet ---> how many tablets do we have?

3,000 milligrams / (300 mg per tablet) = 10 tablets

Hope this helps.

 

[lavenderhearts]

I'm starting to understand this now. Thank you two so much.

 

[lavenderhearts]

How do you know when to use the drops calibrated and infusion rate drops that confuses me?

 

[lavenderhearts]

My problem is I don't know what information to use in a math problem and now I understand the percents are in grams and I have to convert to milligrams.

 

[lavenderhearts]

Thank for helping me with those problems now I have a few more complicated problems that I can't figure out will someone help me.

Questions

1. At 1800 hours a patient was ordered 600mg of a drug to be infused intravenously over several hours. The IV bag contains 0.50% of solution of active drug and the micro-drip (60gtt/min) administration device was set to deliver 30gtt/min. What time will this infusion conclude?
Answer: 10p.m.

2. An IV has been ordered to run for 4 hours at 10gtt/min with a drop factor of 20gtt/mL. The solution in the bag is 750mg of active drug disolved in .5L of D5NS. How many mg of active drug will the patient receive in 2 hours?
Answer: 90mg

3. An IV infusion has been ordered for a patient of 1L of .5% active drug in D5W/10 hours. The administration set is calibrated at 15gtt/mL. What flow rate will be used?
Answer: 25gtt/min

 

[pharmnewbie123]

I believe you're allowed to use a calculator during the exam