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All right, in this lesson we’re going to look through some practice problems for oral medications. I’m gonna use some of the formula as well as some in dimensional analysis because I want you to see both ways worked out.
But first I wanna give you some key points about oral medications that you need to be thinking about, not only when you’re answering questions, but also when you’re doing dosage calculation. If you’re dealing with tablets, remember it could be a whole tablet or a half tablet if it’s scored. But remember that extended release, enteric coated tablets, none of those can be cut.
So if the question says, “How many tablets would this be, is this an appropriate dose?” and it’s one and a half tablets but it’s an extended release, then the answer becomes no because you can’t cut it in half. So keep that in mind.
Capsules, whole capsules only. Liquids might be milliliters, might be teaspoons or tablespoons, make sure you know your conversions, and remember, some of this might be weight-based as well, so make sure you’re thinking about that.
Even with oral medications, you always wanna think, “Is this appropriate?” Again, am I allowed to cut this medication? Does it fit within a dose range? If I need it cut but I can’t, do I need to call a pharmacy because it’s the wrong form? Just things to think about.
And then any time we’re doing these medications, you’re always gonna think per dose, so tabs per dose, milliliters per dose, etc. All right, let’s work some out.
Example number one. The order is for furosemide 60 milligrams, PO q8h. Available is furosemide 20 mg scored tabs. How many tabs per dose?
Let’s start with the dosage formula. Dosage formula says what we want, so that would be 60, over what we have, 20, times what it’s in, one tab. And that gives us, 60 divided by 20, three tabs. Now I wanna show you this in dimensional analysis as well, because remember dimensional analysis can be used for even the most simple problems.
Start with what we’re looking for. We want to find tabs per dose. Transfer your units over. Tabs, one tab is 20 milligrams. Transfer your units up. What do we know? Sixty milligrams per dose, cancel, cancel, tabs per dose, one times 60 divided by 20 divided by one equals three tabs. Same thing, but two different ways to get there, it’s completely up to you on how you wanna do it.
All right, example number two. Diltiazem, 2.5 milligrams, PO q12h. Available is diltiazem five milligrams, scored tabs. How many tabs per dose?
So let’s say what we want over what we have, want, have. Times what it’s in, one tablet, this is what’s available. Two and a half divided by five, 0.5 tabs. Let’s look at dimensional analysis and do the same thing.
We’re looking for tabs per dose. Transfer your top units over, tabs. What do we know? One tab is five milligrams. Transfer your units. What do we know about milligrams? We’re looking for two and a half milligrams per dose. Multiply across the top, divide across the bottom. One times two and a half divided by five divided by one equals 0.5 tabs. Again, your last step is always to verify. Does a half tab of this medication make sense? It’s a scored tab, that seems appropriate, so we would verify, yes this makes sense.
Okay, example number three. Gabapentin 600 milligrams, PO daily. Available is gabapentin 300 milligram tabs. How many tabs per dose?
Now, one thing I would caution you against is some people will look at this and they’ll automatically know the answer because they do math in their head. And that’s fine, but I always encourage you to use a formula or use dimensional analysis as a double check. It’s very possible that you could accidentally flip these. You see this and you go, “Oh, it’s a half a tab,” but you actually got it backwards. So make sure that you’re using your formulas. Let’s do this one more time.
What we want over what we have times what it’s in, which is one tab. Six hundred divided by 300 is two tabs. Make sense? Yes. If you had gone too quickly you could have said half a tab, and you would have been wrong.
Now let’s do dimensional analysis just for the sake of showing you. What we’re looking for is tabs per dose. Transfer your top units over. What do we know? One tab is 300 milligrams. Transfer your units up. What else do we know about milligrams? Six hundred milligrams in one dose. Multiply across the top, divide across the bottom. One times 600 divided by 300 divided by one gets you two tabs. All right.
Great, example number four. Ibuprofen 100 milligrams, PO one time. Available, Ibuprofen 20 milligrams per mL suspension. How many teaspoons per dose?
Okay, so identify, convert, solve, and verify. We’re identifying, what are we looking for? We’re looking for teaspoons. Do we have teaspoons? No, we have milliliters. In this case, it may be easier to find your milliliters and then convert, but you can do it either way you want. I’m actually going to convert after I solve.
So, what I want, 100 milligrams, over what I have, 20 milligrams, times what it’s in, one milliliter. One hundred divided by 20 gets me five, that leaves me with five milliliters. Then you have to convert this to teaspoons. How many teaspoons is five milliliters? One teaspoon. So this is your verify step, are you in the right units? I see this a lot, people get to this part and they forget to convert back to teaspoons at the end, so part of verify is are you in the right units.
I wanna show you this in dimensional analysis because one of the benefits of dimensional analysis is not having to do separate conversions. So let’s look at it this way.
What are we looking for? Teaspoons per dose. Transfer our top units over, teaspoons. Do we know anything about teaspoons here? Nope. So let’s convert. One teaspoon is how many milliliters? Five. Now transfer our milliliters over. What do we know about milliliters? One milliliter is 20 milligrams. Transfer units over. What do we know about milligrams? We want 100 milligrams in one dose. Multiply across the top, one times one times 100. Divide across the bottom, divided by five, divided by 20, divided by one. Gets us one teaspoon per dose. Again, cancel milligrams, cancel milliliters, you can see you’re left with what you’re looking for.
Let’s do one more. Azulfidine 1.5 grams PO daily. Available is 500 milligram capsules. How many caps per dose? So again, identify, convert, solve, and verify. Identify: we are looking for capsules per dose. We’ve got grams here, we’ve got milligrams here. So we’re kind of aware something’s going on. Convert: I need both of these to be in grams or in milligrams. It’s completely up to you what you choose to do. Personally, I’m gonna put everything into the unit of the actual order, because I feel like that makes more sense.
So instead of 500 milligrams we’re gonna say that these capsules are 0.5 grams. Move over three spaces, 0.5 grams. Now I can work on solving, I’m gonna use my dosage formula. What do I want, 1.5 grams. What do I have, 0.5 grams in one capsule. 1.5 divided by .5 gets us three. Now, if you had chosen to do this the other way you could have also said that this was 1500 milligrams, therefore you would have said 1500 milligrams over 500 milligrams, what I want over what I have, times what it’s in, and you would’ve gotten the same answer, three capsules.
Now, let’s see what this looks like in dimensional analysis, again, not having to do separate conversion, it takes one step out of the process. I’m looking for caps per dose. Transfer my units over. What do I know about capsules? I know that one capsule is 500 milligrams. Do I know anything else about milligrams? Nope, so I have to convert. A thousand milligrams going to grams is one gram. What do I know about grams? Transfer the units. I know that I want 1.5 grams per dose. Cancel, cancel. I’m left with caps per dose, and I’m good to go. One thousand times 1.5 divided by five gives us three capsules.
Okay? So either way works. Again, I want you guys to just find the process that works for you, go back and review these. We’ve provided these without answers in the outline if you want to review them again and do them yourselves. The more you can practice, the better you’ll get at them.
We love you guys, make sure you’re continuing to work on these dosage calculations. Now go out and be your best selves today, and as always, happy nursing!