Pharmacy Technician University

There’s no doubt about it. In my time training people to be pharmacy techs THE biggest stumbling block was calculations. If you are in that boat then I think you’ll appreciate the next set of ‘tutorials’ on this site where I’ll be working through some basic calculation issues.

My original intent was to work through these problems using a video camera and me working them out on paper. I’m still going to do that. But, for the time being I’m just going to put some basic problems in a text format so at least you can get started with them.

Let me point out one thing. This is a ‘rule’ I taught all my techs and it seemed to help them. It’s this: when you are working a problem and you are stuck, it’s probably because you don’t know what you are solving for.

In short, START WITH THE END IN MIND.

Here’s today’s example to drive the point home.

Let’s say you get this prescription:

Amoxicillin 125mg/5ml
sig: ss tsp tid x 10days

But, we have a problem in the pharmacy: for some reason ‘someone‘ forgot to order the 125mg strength. So, we’re left with the 250mg/5ml strength in 100ml bottles. You, as the tech taking the prescription, should be able to solve for this and figure out how much to dispense and get it down the line.

Granted, for someone experienced reading this is NOT a difficult problem. For others, they see that they have to use a different strength and get twitterpated and can’t get going.

Remember, start with the end in mind and solve for that.

So, what do we want to know? We want to know how much of the available drug (both directions and quantity) to give to the patient.

You can solve for this a couple of different ways. But here is how I’d recommend you tackle something like this. First of all, figure out how many mg the doctor wants the patient to be taking with each dose.

We already have the directions: the patient is to take ss tsp tid of the 125mg/5ml strength. SS is 1/2 and tsp is teaspoonful. A teaspoonful is 5ml. So, the patient should get 2.5 ml of the 125mg/5ml strength three times daily.

That means the patient should be taking 75mg (125mg/5ml and they need 2.5 ml=75mg) three times a day (tid).

Now, it’s simply a matter of converting using the 250mg/5ml strength.

So…

We now want to know how many ml in each dose. That’s what we want to solve for. To do that we can set up a ratio, which is a little hard to show here and frankly, not needed. Instead, take the amount of mg/ml of our current strength. So, if we have a bottle with 250mg/5ml that means there are 50mg/ml (250mg divided by 5ml).

If each ml of amoxicillin has 50mg then to get our 75mg dose that we solved for above we simply need 1.5ml three times daily of our new strength.

Again, I will be putting video’s up in the future. But hopefully this short article give you a little feel for my thought process in solving calculations. Granted, there are other ways but it’s helpful to start with the end in mind.