Phosphate calculation problem Rxprep page 24

[Elmoy]

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Could you please solve and explain this problem: Rxprep 2011 edition, page 24

The pharmacist has calculated that the patient requires 30 mmol of phosphate and 80 mEq of potassium. How much potassium phosphate and how much potassium chloride will be required?

 

[farmadiazepine]

That's a terrible question in RxPrep. I would simply skip it if I were you. I thought they forgot to give you information or something.. But yet again I don't remember too well cuz I took NAPLEX earlier this month.. Skip it.

 

[Elmoy]

That's a terrible question in RxPrep. I would simply skip it if I were you. I thought they forgot to give you information or something.. But yet again I don't remember too well cuz I took NAPLEX earlier this month.. Skip it.

Congratulations for passing both Naplex and MPJE!!!

Thanks for your recommendation.

 

[poda521]

Yeah, I just looked at that question and it is extremely confusing.

Either they forgot to mention some other information or they just jumbled 2 questions into one, where the explanation to the answer delves straight into another question.

 

[LearnerSharer]

Question was:
The pharmacist has calculated that the patient requires 30 mmol of phosphate and 80mEq of potassium. How much potassium phosphate and how much potassium chloride will be required?


My Reasoning process of the answer:

3mmol of phosphate-4.4 mEq potassium/ml.

WHAT DOES ABOVE LINE MEAN?



FACT 1: You can buy: Potassium phosphate:

How is it sold?

In 1 ml of liquid, you get: 3 mmol ofphosphate and 4.4 mEq of potassium.



(Or, for each mmol of P04, you are adding 1.5mEq of K + .)

WHAT DOES ABOVE LINE MEAN?

Based on fact: In 1 ml of liquid, you get: 3 mmol of phosphate and 4.4 mEq of potassium.

We get ratio of phosphate (= PO4) and potassium (= K+):

When you buy: 1 mmol of P04

you also get: 1.5 mEq of K +.



Potassium chloride: 2 mEq potassium chloride/ml

WHAT DOES ABOVE LINE MEAN?

FACT 2: You can buy: Potassium chloride:

How is it sold?

In 1 ml of liquid, you get: 2 mEq POTASSIUM CHLORIDE.



Okay,I bought 2 products:

POTASSIUM PHOSPHATE

and

POTASSIUM CHLORIDE.



Now,how do I give to patient?



Patient needs POTASSIUM and PHOSPHATE.

To supply PHOSPHATE, I can use product: POTASSIUM PHOSPHATE.

To supply POTASSIUM, I can use product: POTASSIUM PHOSPHATE or POTASSIUM CHLORIDE.



The key in common: POTASSIUM.

When we give POTASSIUM PHOSPHATE, we are giving POTASSIUM and PHOSPHATE.



But,this patient needs more of POTASSIUM? Which product do I give?

I know I should NOT re-give POTASSIUM PHOSPHATE AGAIN because I will OVERDOSE the patient on PHOSPHATE.



So,to give more POTASSIUM, I have to use another product.

Luckyme, I bought POTASSIUM CHLORIDE.

So,to give MORE POTASSIUM, I will use POTASSIUM CHLORIDE.



So,here are the step:

STEP1: FOCUS: PHOSPHATE. To give PHOSPHATE (in terms of mmol), FIND: milliliter of POTASSIUM PHOSPHATE.

STEP2: FOCUS: POTASSIUM: DID GIVE. Based on answer of STEP 1, FIND: I gave some POTASSIUM, how much of POTASSIUM did I just gave (in term of mEQ).

STEP3: FOCUS: POTASSIUM: WILL GIVE. Wait, patient needs more. So, FIND: how much MORE that I have to give (in term of mEQ).

STEP4: FOCUS: POTASSIUM: WILL GIVE. FIND: how many milliliter of POTASSIUM CHLORIDEwill give me that much mEQ of POTASSIUM.



Insummary,

RECOGNIZE😛OTASSIUM COMES FROM 2 SOURCES.



By giving PHOSPHATE from POTASSIUM PHOSPHATE, I already gave POTASSIUM.

To give MORE POTASSIUM, I can NOT re-give POTASSIUM PHOSPHATE. Why? I will OVERDOSE the patient on PHOSPHATE.

So, to give MORE POTASSIUM, I have to give POTASSIUM CHLORIDE.

Now, with those REASONING in mind, please go back to the answer and see them again.

Goodluck.

 

[Gozchi]

Could you please solve and explain this problem: Rxprep 2011 edition, page 24

The pharmacist has calculated that the patient requires 30 mmol of phosphate and 80 mEq of potassium. How much potassium phosphate and how much potassium chloride will be required?

Admittedly, the question was badly set; took me a while to figure it out. Each 1 ml of Potassium Phosphate contains 3mmol phosphate and 4.4mEq of potassium. Since we need 30 mmol of phosphate, 10 ml of potassium phosphate will meet that need. But at the same time that same 10 ml contains 18 ml of potassium (using dimensional analysis) which is the equivalent of 80mEq, since every 1 ml contains 4.4mEq of potassium.
Answer - 10ml potassium phosphate; 18ml potassium chloride. Good luck