Category Archives: RxCalc

Who is Hayseed?

Hayseed is a one person shop, run by me, Rob Fahrni.

I’ve registered a few domains over the years with the thought of starting an Indie development shop.

The first was Pneumatic Industries. At that time in my life I was a hardcore Windows developer working on a product called Visio. My ideas then centered around the creation of a Windows API/C++ application that could track pesticide use for framers and Pest Control Advisors. This desire was derived from my years of working on Ag products at AgData. Way down the road I’d work for a little company called Agrian that would deliver everything I could have dreamed of and a whole lot more.

My next venture was Apple Core Labs. I started it to develop iOS Apps for myself and others. The fruits of that effort were the creation of RxCalc (please forgive the outdated site) and Arrgly.

I created RxCalc with my brother Jay so he could do Pharmacokinetics calculations at the hospital. Jay sat next to me and we wrote the math for the app in C++ because the original code was going to run on Palm PDA and Windows, which it did, I just never built the UI for it.

Enter the iPhone. When we saw that and Apple shipped an SDK for it I immediately set out to make an iPhone version. The C++ came over no problem, the UI took me forever to build. On July 4, 2009, RxCalc made it debut in the App Store. It’s been there ever since.

I did a bunch of contract iOS work under that moniker, I don’t think any of it exists today, which is a real shame.

Ultimately I failed to make consulting work for me. Too much time away from family and too many hours not working on the things I wanted to build.

Enter Hayseed. I dropped the name Apple Core Labs and started operating under the name Hayseed. Why Hayseed? Well, a hayseed is a derogatory term for someone who isn’t so bright. I see myself has a digital hayseed. I don’t take offense to the term. I’m not sophisticated or the brightest bulb in the box, so I found it fitting, and it just so happened when I went to buy a domain name hayseed.co was available, which was perfect and surprising all at the same time.

Under the Hayseed name I spent a couple years, an hour here, hour there, building Stream, my feed reader. It is, by far, my favorite project to date. I’m really happy with the way it turned out. It did everything I wanted from a feed reader. It may not be wildly successful, but that’s ok, it lives on and I continue to work on it, ever so slowly, to improve it and add features.

Some day I hope to make Hayseed my full time job. My plan is to make it my retirement job. If it happens sooner, by some miracle, that would be great.

In the meantime I have a couple products I’d love to see y’all use. For the Clinical Pharmacists out there please give RxCalc a try. If you are a blogger or avid reader of news, please give Stream a try.

Please send any feedback you may have directly to hello@hayseed.co. I love getting it, even if it’s bad, but I much prefer positive feedback. 😃

If you’d like to support my little projects you can purchase RxCalc directly in the App Store for $2.99, leave a tip for me in Stream by going to Settings > Tip Jar, or support me directly through my Ko-fi account.

Help Wanted: RxCalc 1.3 Beta Testers

We Want You

We’re working on an update to RxCalc to address some minor UI issues on the iPhone 5 and iPod Touch. If you’re interested in helping us, please click this link and follow the instructions.

What’s changing? Good question, it’s very minor:

  • Requires iOS 5
  • Now using the numeric keypad for data entry
  • BUG FIX: Some views clipping on the iPhone 5

We’re also working on a feature update, we’ll share more on that later.

Calling all RxCalc Users

It’s been a while since we updated RxCalc and we’d like to know what you, our users, would like to see in a new release. We’re definitely interested in making RxCalc what you want.

Would you like different Pharmacokinetics Algorithms? We currently use Creighton, but we could implement others.

Would you like TPN support? Are there general usability changes you’d like to see? How about email support? Maybe templates for commonly used starts?

Let us know, we’re listening.

Another Bad Review

We’re a bit bummed at the moment, we must admit. We haven’t checked the App Store for RxCalc reviews in quit a while, so we decided today would be the day. It was not encouraging.

In part the reviewer “found it less than useless.” Ouch. That statement really cuts to our heart. We want RxCalc to be your “go to” Pharmacokinetics calculator, we really do. We believe it to be accurate.

What do you do when you get a review like this? In our case, nothing. The reviewer didn’t contact us. We can’t fix what he, or she, sees as a problem because we don’t know what that problem is.

So, TXRph, if you see this, please contact us at support@applecorelabs.com, and tell us what’s wrong. If you can, please provide us with your calculations and what you expect them to be. We really want to get this stuff right. We have a PharmD on staff that verifies the calculations by exercising our algorithms, of which there are many different methods. Could it be your teaching lead you to expect a different set of numbers? Maybe, maybe not. If you see this, please, let us know how we can fix it.

There are thousands of users of RxCalc out there. We rarely get ratings from our users. It seems that we only hear from users that have a bad experience.

Take that how you will. We’d love to hear from you, good or bad.

Pretty please, with sugar on top.

We have a favor to ask. If you use RxCalc and have left a review in the App Store, please, get in touch with us. We’d love to have a conversation with you.

We have a bunch of great ideas for RxCalc but we’d like to put those on hold until we can resolve what folks see as under dosing. We’re pretty sure it has to do with the algorithm, or method of calculating kinetics, we chose to use, but until we hear from some of you we can’t be sure.

A wonderful boquet of flowers.So, please, drop us a line at one of our support e-mail addresses, or you can contact me directly at rob@applecorelabs.com.

Thank you.

The App Store Disconnect

My frustration with the disconnect between us and our customers on the App Store continues to grow. For RxCalc we typically see ratings that have to do more with lack of features, or new features, than the features we actually have. Don’t get me wrong, that’s great! The problem is we have NO way of communicating with these users to find out what they really want. We can make an educated guess and hope we’re correct, but that’s the best we can do.

Take a look at one of our latest ratings. It’s not horrible, three stars, but this person would like something added to the app. Based on this comment we have little to no idea what they’re really after.

“I found that when using 2 levels to calculate phamacokinetics that the VD is way off from any equations I have seen. Also it does not extrapolate a Cmin and Cmax. This program is useful for calculating first doses. I hope this can be fixed in the next update since this is the only kinetic program I could find for the apple”

In this case the user is probably used to using a different equation, or method, to determine dosing. As we’ve explained here before we use Creighton vancomycin calculations, but there are many others. Different method, different results.

If Apple would allow us to make contact with our reviewers we could actually bring some of these requests to life! As it sits today, we can only hope they’ll make contact via our support page, or we can make our best guess at their request.

That’s not so good.

Hello 1.2!

It’s been a few months in the making but RxCalc 1.2 is now available in the App Store.

What’s new? Glad you asked. There are two new features to talk about.

  1. Support for dosing adjustment using single level vancomycin kinetics.
    • The calculations are performed using both patient specific information supplied by the user as well as patient population parameters.
  2. Literature supported High Dose Extended Interval (HDEI) (aka “once daily” or “pulse”) aminoglycoside dosing.
    • Calculations for gentamicin and tobramycin are based on 7mg/kg adjusted body weight.
    • Calculations for amikacin are based on 15mg/kg adjusted body weight.

This release was also unique because we finally opened the door to a Beta Tester. Our heartfelt thanks goes out to Robert B. Martin, Pharm.D. Robert provided a critical eye for Jerry’s Pharmacokinetic Calculations and his years of clinical experience were priceless. He’s given us a lot of great feedback we’ll be sure to include in future releases. That’s right, we like to hear from our users!

We hope you enjoy using 1.2 as much as we enjoyed developing it.

Yes, and No

Something we need to do here at Apple Core Labs is create a FAQ for RxCalc. I’ve been saying that for quite a while now but I just haven’t gotten around to it. It’s one of those things that falls to the bottom of the list, but it really is time I did it.

Why?

A bouquet of flowers.We need to get this hammered out so we avoid bad reviews to be quite honest. Our calculations are accurate but we continue to receive reviews that say otherwise. There is no one true method for deriving Pharmacokinetics calculations. There are many methods. To say RxCalc under doses is true, and false, all at the same time. If you’re a new Pharmacist, or married to a particular method, you may be extremely disappointed with the numbers RxCalc produces.

By creating a FAQ the hope is we’ll help remove that disappointment. RxCalc currently uses the following Creighton formulas for vancomycin calculations:

  1. Cockcroft and Gault equation using IBW for creatinine clearance (use ABW if less than IBW)
  2. Elimination rate constant: ke = (0.00083 * CrCl) + 0.0044
  3. RxCalc considers the total dose of vancomcyin per dosing interval determined by equation; in this case [(ln Cp-ln Ctr)/ke] for the interval and [Cp*Vd*(1-e-^(ke*tau))] for the dose.
  4. Vd is defaulted to 0.7 liters/kg, but can be changed to the users taste between 0.5-1 liter/kg

Vancomycin dosing is so variable, and there are so many methods, that it was difficult to chose just one. Methods for vancomycin kinetics include Bauer, Burton, Matzke, Moellering and Winter just to name a few. At the time RxCalc was designed the Apple Core Labs team felt most comfortable with the formulas dervied by Creighton. This choice was neither right nor wrong as vancomycin kinetics are as much an art form as they are a science. You will find many different methods used throughout the various schools of pharmacy and medical centers in the United States.

With that said, Apple Core Labs chose to offer an adjustable volume of distribution for RxCalc, in effect giving the end user an amount of flexibility in their calculations. The option to set your default volume of distribution from 0.5 liters/kg to 1.0 liters/kg can make a significant difference in the final outcome of your vancomycin calculations. RxCalc relies not only on numbers to perform calculations, but the end user’s clinical acumen and experience as well.

Apple Core Labs will continue to improve RxCalc by adding features and improving functionality. We appreciate any and all feedback, no matter how good or bad. One thing we would like to request from our end users is detailed information included with their comments. If we know what method the user is comparing the results generated by RxCalc to, we can better understand what the problem might be and how best to help.

On the flip side

I give that a thumbs up!

Yesterday I shared a frustration, today, I’ll share one of those happy moments. We were bumming over the bad review, and have been for a few days, when what appears in one of our mailboxes? That’s right, some positive feedback, and a feature request! Woo-hoo!

Thank you for offering such a usable app. I hope you will continue developing others as clinically useful as RxCalc.

Thanks for that! It’s nice to hear something positive after getting a bad review.

Oh, what did he ask for? Glad you asked.

I seldom order peak levels anymore except in certain cases. As you know, most of the time we can do a very good job dosing and monitoring vanco patients with trough levels only. Because RxCalc requires both peak and trough levels in order to use the “Adjust with Levels” portion of the app, I am rarely able to use this feature. Is there any way to allow the peak level input to be optional?

Ahh, just you wait.