Hi, this is Cathy with Level Up RN. In this video, I will be going over a dosage calculation problem involving an oral medication, specifically a tablet or capsule. I'll be solving this problem on my whiteboard using three different methods including dimensional analysis, ratio and proportion, and the formula method. You can find all the information that I'll be covering in this video in our Level Up RN dosage calculation workbook. If you are in nursing school, then you know how important it is to master dosage calculations, and our workbook will help you do just that. In a nutshell, our workbook contains all different types of dosage calculation problems that you are likely to encounter in nursing school and we demonstrate how to solve each problem using multiple methods, so you can pick the way that makes the most sense to you.
All right. So with this problem, we have an order for ciprofloxacin 0.5 grams PO BID, so twice a day. What we have available is ciprofloxacin in 250 milligram tablets. And we're being asked, "How many tablets do we administer per dose, and how many tablets do we administer per day?" So for Part A of this problem, I can solve this with dimensional analysis, ratio and proportion, or the formula method.
So let's first solve it with dimensional analysis. So I'm going to put a little DA there. So with dimensional analysis, I start by putting down what is ordered. So what is ordered is 0.5 grams. Now I check to see if I need to multiply times any conversion factors. So if I look at what's ordered, that's in grams, but what I have available is in milligrams. So I do need to multiply times a conversion factor. So I'm going to multiply times this conversion factor. 1 gram equals 1,000 milligrams. And my grams will cross off, and I'm left with milligrams. Now I'm ready to multiply times our available concentration, which is one tablet, and each tablet contains 250 milligrams. So my milligrams cross off, and I'll be left with tablets, which is what I was looking for. So with dimensional analysis, it's important that you set up everything correctly so that your like units cross off, and you're left with the unit of measure that you're looking for. So if you multiply this out, we end up with two tablets.
All right. So let's work through the same problem with ratio and proportion. Okay? So the first thing we're going to do with ratio and proportion is, really, actually convert this dose up here, the 0.5 grams, because we need all our units to be consistent. So we can't have grams and milligrams. We need to have milligrams being compared to milligrams. So the first thing we're going to need to do is take that 0.5 grams and turn it into milligrams, which is 500 milligrams. Now we can set up our ratio. So on one side of the equation, we have our known ratio. So we know that there is 250 milligrams in a tablet. We want to give 500 milligrams, and we don't know how many tablets that will take. So with ratio and proportion, we're going to cross-multiply. So 250X equals 1 times 500, so 500. And then you solve for X. So 500 divided by 250 equals 2. Two tablets. So you can see we've got the same answer as we did with dimensional analysis. A few more steps, but you do have flexibility on how you set up your ratios. I could have had this flipped. I could have had one tablet on top and 250 milligrams on bottom, X tablets on top, and 500 milligrams on bottom. You have less flexibility when it comes to dimensional analysis as far as how you set up your equation. But this takes more steps. So really, you have to figure out what method makes the most sense for you.
All right. Lastly, let's do this problem with the formula method. So the formula method has desired over half times the vehicle. So when we're using this method, we have to convert our units, just like we did with ratio and proportion. I need to make sure my desired and have are the same units. And right now, my desired is in grams, and what I have is in milligrams. So again, I would need to convert that 0.5 grams to 500 milligrams. Now I'm ready to plug that into the formula. So desired is 500 milligrams. What I have is 250 milligrams, and my vehicle is in one tablet. So by vehicle, I mean how are we getting this dose into the patient? So we have 250 milligram tablets, so that tablet is the vehicle. When we are going over liquid oral medications, the vehicle might be like 5 milliliters or 10 milliliters. You might have to get that dose in a-- you're getting that dose in a solution, so your vehicle will be different. But in this case, it's one tablet. So if we do this math, we end up with two tablets. So that's a third way to solve this problem.
Okay. What about Part B? Part B asks us, "How many tablets do we administer per day?" So per the order, we need to give this medication BID, which is twice a day. So if we're giving two tablets per dose and we are giving that two times a day, then we are giving four tablets over the course of the day.
