NABP NAPLEX Exam - Topic 2 Question 105 Discussion

Actual exam question for NABP's NAPLEX exam

Question #: 105
Topic #: 2

LN is 84 YOM who is in hospital for a back surgery. His height is 5 feet and 4 inches, weight 85 kg and NKDA.

His past medical history includes hypertension, diabetes mellitus, major depression, hypothyroidism and chronic back pain. Post-op day 1, LN's medication includes Dexamethasone 8mg iv q6h with taper dosing, Ondansetron 4mg iv q6h prn for N/V, Levothyroxine 0.075mg po daily, Lisinopril 10mg po daily, Citalopram 20mg po daily, Docusate sodium / Senna 1 tab po twice a day, Bisacodyl 10mg suppository daily prn for constipation, Famotidine 20mg iv q12hr, Metoclopramide 10mg iv q6h, Metformin 500mg po bid, D51/2NS with 20K at 125mls/hour and Hydromorphone PCA at 0.2mg/hour of basal rate, demand dose 0.1mg. lock-out

every 6min, one hour limit 2.2mg/hour. Pertinent morning labs includes serum creatinine 1.4mg/dl, Mg 1.5mg/ dl, K 5.0mmol/L, Na 135mmol/L. The bioavailability of levothyroxine is roughly 50%.

The physician requests you for a dose recommendation to convert her home dose of 75mcg po daily to intravenous.

What would be the appropriate intravenous dose?

A37.5mcg

B75mcg

C75mg

D150mcg

E37.5mg

Show Suggested Answer

Suggested Answer: A

Since the bioavailability of levothyroxine is roughly 50% (given in the Question:). To convert

the home dose to intravenous, it would be 50% of the oral dose. So 50% of oral 75 mcg would be 37.5 mcg intravenously.

by Chi at May 02, 2025, 09:23 PM

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Lore

5 months ago

I agree, 37.5mcg makes sense for the conversion.

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Nickole

5 months ago

Wait, are we sure about that? Seems low.

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Bobbye

5 months ago

Definitely should be 37.5mcg for IV!

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Ressie

6 months ago

75mg? That can't be right, right?

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Tora

6 months ago

The bioavailability of levothyroxine is about 50%.

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Alease

6 months ago

I recall a similar practice question where we had to convert a medication based on its bioavailability. I think it was straightforward, but I can't remember the exact numbers.

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Kristofer

6 months ago

I think the answer might be 37.5mcg since we usually halve the oral dose due to the bioavailability, but I could be wrong.

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Elenor

7 months ago

I’m a bit unsure about the exact conversion. Is it just half the oral dose for IV, or do we need to consider something else?

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Mari

7 months ago

I remember we talked about converting oral doses to IV, especially with levothyroxine. The bioavailability being 50% is key here.

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Jeannetta

7 months ago

Okay, I've got this. The patient is on 75 mcg of levothyroxine orally, and the bioavailability is 50%. So to get the equivalent IV dose, I need to double the oral dose, which would be 75 mcg x 2 = 150 mcg. That's my final answer.

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Paola

7 months ago

Whoa, this is a lot of information to take in. I'm feeling a little overwhelmed trying to figure out the right IV dose. Maybe I should review the key details again and see if I can break it down step-by-step.

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Jesusita

7 months ago

Alright, I think I've got this. The oral dose is 75 mcg, and the bioavailability is 50%, so the IV dose should be 75 mcg / 0.5 = 150 mcg. That's my best guess.

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Elliot

8 months ago

Hmm, this is a tricky one. I'm not sure if I should just double the oral dose or if there's some other calculation I need to do. I'll have to think this through carefully.

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Adelle

8 months ago

Okay, let's see here. The patient is on 75 mcg of levothyroxine orally, and the question is asking for the appropriate IV dose. Since the bioavailability of levothyroxine is roughly 50%, I'll need to double the oral dose to get the equivalent IV dose.

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Veronika

12 months ago

Okay, let's see... 75mcg it is! I'm not about to give this poor guy a massive overdose of thyroid medication. Although, a dose of 150mcg might just give him the superpower he needs to lift that hospital bed with one hand.

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Darnell

10 months ago

User 3: Definitely, let's go with 75mcg.

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Gretchen

11 months ago

User 2: Agreed, we don't want to risk overdosing him.

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Shaun

11 months ago

User 1: I think 75mcg is the right choice.

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Artie

12 months ago

Ah, the good old levothyroxine conversion trick! I bet the patient would love a 37.5mg dose, that's sure to keep their thyroid in check. Who needs a functioning metabolism anyway?

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Rory

11 months ago

User 2: Yeah, that sounds about right. It's important to get the dosage just right for thyroid management.

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Izetta

12 months ago

User 1: I think the appropriate intravenous dose would be 37.5mcg.

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Georgeanna

1 year ago

I'm not sure about that. I think the correct intravenous dose should be 75mcg to maintain the same therapeutic effect.

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Jenelle

1 year ago

I agree with you. Since the bioavailability of levothyroxine is roughly 50%, we should halve the dose to 37.5mcg.

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Casandra

1 year ago

I think the appropriate intravenous dose would be 37.5mcg.

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Melvin

1 year ago

Hmm, this is a tricky one. I think the answer is B) 75mcg, since the bioavailability of levothyroxine is roughly 50%. Can't go with the mg option, that's just silly.

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