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Skip to 0 minutes and 20 secondsOK. So what we're looking at here in the initial box which is in grey, is an extract of the pharmacy system for your hospital for January, 2015. And it's showing for ciprofloxacin. It's showing that there are a number of different formulations. There's IV infusion, there are tablets, and there's a oral suspension. It also shows that for many of these there are different strengths and there are different pack sizes. But importantly, it shows for the month of January the number of each pack size which has been issued. So for example, if we choose the example of ciprofloxacin tablets 250 milligrams, in packs of ten. There were 53 issued during that month.

Skip to 1 minute and 3 secondsThe first step, and it's only to make life just a little easier, is to bring together the IV infusions together, the various pack sizes and strengths of tablets together, and of course we have the single oral suspension here at the bottom. So we now begin to calculate the number of DDDs. So let's continue an example using the ciprofloxacin tablets, 250 milligrams of packs of ten. Of which there were 53 issued in January. We want to work out the total number of milligrams, so there were 53 packs of ten tablets. Each tablet contains 250 milligrams.

Skip to 1 minute and 37 secondsTherefore the total number of milligrams of ciprofloxacin is 132,500 and we can do that same calculation for all the different formulations and pack sizes of ciprofloxacin. You must remember the DDD for ciprofloxacin is and grams not milligrams. Therefore the next step is simply to convert from milligrams to grams by dividing by 1,000. So again, we'll continue our example of the tablets in packs of ten, and so that's 132,500 divided by 1000. Giving us a total of 132.5 grams. And again, column I here shows that same calculation being done for all the different pack sizes. The next step is to begin to bring together the total number of grams for each of the forms.

Skip to 2 minutes and 29 secondsWe need to remember that ciprofloxacin is one of those antibiotics where there is a different DDD for IV forms and oral forms. So let's consider firstly the IV forms. We bring together the total number of grams, the 2.4, the 7.4, and the 12.4. That gives us a total of 22.2 grams. And similarly we can add up all of the number of grams for all of the oral formulations. It's a much bigger number over 1,202.2 grams. And the next step is then to work out the number of DDDs. So we take the 22.2 grams, the DDD for ciprofloxacin is 0.5 grams. Therefore there is a total of 44.4 DDDs. Similarly for the oral forms is a total of 1,202.2 DDDs.

Skip to 3 minutes and 21 secondsThat gives us a grand total of 1,246.2 DDDs of ciprofloxacin for the month of January, 2015.

Total DDD

By now you will have gained an understanding of what DDDs are and how they are calculated.

This brief exercise will build on this introduction.

In the video you will be taken through a worked example of the number of doses of ciprofloxacin issued by the pharmacy to a particular hospital ward in January 2015, and how these data can be used to work out the total number of DDD for that month.

On the next step you will be given the data for February 2015 and asked to work out the total number of DDD for that month.

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This video is from the free online course:

Antimicrobial Stewardship: Managing Antibiotic Resistance

University of Dundee