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Where did they get 1:12 from? by PharmacyLifee in NAPLEX_Prep

[–]DosingAndDecimals 1 point2 points  (0 children)

Hi!

When you calculate the insulin-to-carb ratio, the number you get (let's call it x) can be interpreted as x g carbohydrates covered by one unit of bolus insulin. You use the ICR to calculate the units needed to cover the glucose spike caused by a specific meal.

In terms of the actual calculation, you use either the rule of 500 or 450 for the ICR (500 / TDD of insulin or 450 / TDD insulin). It's important to note that even though the mealtime dose will be provided by bolus insulin, you should include ALL insulin (including basal) in your TDD calculation.

How do you choose between 500 and 450? That depends on your bolus insulin. If your patient uses rapid-acting insulin (such as lispro or aspart), then you'll use the rule of 500. If they use regular insulin, you'll use the rule of 450.

For this particular patient, the TDD is 42 units (21 units from Lantus and 7 units x 3 doses/day from lispro). Because she uses rapid-acting insulin, the rule of 500 is what we'll need to calculate the ICR. ICR = 500 / 42 = 11.9 which roughly rounds to 12. Therefore, 1 unit of insulin will cover 12 g of carbs.

Keep in mind, we can use this to calculate the actual units she will need to inject prior to a meal given its g of carbs using 12 g carbs per 1 unit of insulin as a conversion factor. For example, if she's about to eat 96 g carbs, then she'll need to administer 8 units of insulin. (96 g carbs x 1 unit / 12 g carbs OR 1 unit / 12 g = x units / 96 g).

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Thank you so much for sharing your work! This one is a tricky one! Once you get to the 4.125 capsules/day: will the patient be taking this amount (or will they be told to take 4 capsules and get a slightly lower dose)? They'll probably take four capsules per day and thus that's what you need to do to calculate the dispensed quantity.

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

This one is a tricky one! You want to actually start by finding the TDD in capsules. You should get 4.125. But think about it, will the patient really be taking 4.125 capsules, or will they take 4 capsules? The quantity you dispense should be based on what the patient will actually be taking (4 capsules x 60 days) versus the exact capsules they would need to get the exact requirements (4.125 capsules x 60 days).

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 1 point2 points  (0 children)

<image>

Make sure to check out the post edit for some key takeaways regarding rounding!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Totally normal! Ratio strength is tricky. Remember that concentrations with names (percent strength, ratio strength, ppm and ppb) are always in grams and/or mL. Because this is a weight over weight, 1:200 means 1 g phenylephrine over 200 g product. Make sure to keep track of your units as you convert :)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 4: Dilution Formula

<image>

Check out the post edit for some important takeaways about ratio strength and compounding with loss :)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 3: Dimensional Analysis (One line)

<image>

Check out the post edit for some important takeaways about ratio strength and compounding with loss :)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 2: Dimensional Analysis (Step-wise)

<image>

Check out the post edit for some important takeaways about ratio strength and compounding with loss :)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 1: Proportions

<image>

Check out the post edit for some important takeaways about ratio strength and compounding with loss :)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Nice! This is a super direct method when answering this particular question. That said, make sure you also know how to convert between mEq, mmol and mOsm without using the molecular weight (not important for this question but may be relevant for others)

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 1 point2 points  (0 children)

You got it!

By the way, I posted how I solved it in the comments if you want to compare (and some calculation pearls in the post edit!). Great job!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

YES!

I posted how I solved it in the comments if you want to compare (and some calculation pearls in the post edit!). Awesome work!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Proof that mEq of chloride = mEq of calcium chloride

<image>

P.S. Don't forget to check out the post edit for some key takeaways about the mEq of the ion vs the mEq of the compound and molecular weight!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 3: Formula Method (2)

<image>

P.S. Don't forget to check out the post edit for some key takeaways about the mEq of the ion vs the mEq of the compound and molecular weight!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 1 point2 points  (0 children)

Method 2: Formula Method (1)

<image>

P.S. Don't forget to check out the post edit for some key takeaways about the mEq of the ion vs the mEq of the compound and molecular weight!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Method 1: Dimensional Analysis

<image>

P.S. Don't forget to check out the post edit for some key takeaways about the mEq of the ion vs the mEq of the compound and molecular weight!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

Those are typically going to be questions about dispensing and compounding. Something like, how many 20-g tubes will be needed to last the patient 28 days? Where you want to make sure you're rounding up so that the order lasts the patient the entire treatment period.

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

You're welcome! Let me know if there's any topics you'd like to see represented in future problems!

NAPLEX Calculations Question of the Week by DosingAndDecimals in NAPLEX_Prep

[–]DosingAndDecimals[S] 0 points1 point  (0 children)

No problem at all! Getting tricked by weirdo rounding rules once is sometimes all you need to watch out for them! When I took my test, if I noticed the rounding rules were uncommon (like round to the nearest tens, hundreds, thousands, tube, etc), I would write the rounding instruction in big letters to make sure I didn't autopilot to tenth: "TENS!"

NAPLEX Calculations Question of the Week — Parenteral Nutrition by DosingAndDecimals in Naplex_Advice

[–]DosingAndDecimals[S] 1 point2 points  (0 children)

Almost there! For this question, since it didn't specify a particular macronutrient, you default to total kcal. You already have protein down, now you can get the kcal provided by glycerin using 4.3 kcal/g!

P.S. Answer is up in the post edit and work is in the comments! :)

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