Reviewing my search console report today I found the most linked page on my web site is my review of AUC guided dosing of vancomycin.

In the top linked text section I found “how precisepk helps pharmacist compliance”.

So naturally I pulled up their web site and found this insightful graph.

As you can see, APK performs better than all except precise. The reason for its claim to greater accuracy is simple, they use a 2-compartment model.

I have mentioned this numerous times but it bears repeating, the one compartment pk model for vancomycin always underpredicts “true” AUC because it excludes the distribution phrase.

My contention is that over-estimating AUC, as precise sometimes does, may result in subtherapeutic dosage regimens.

DoseMe, Insight, and Precise are an order of magnitude greater in cost than APK. BestDose (formerly USCPACK) has been in development for decades and is still not ready for prime-time.

If you need a pk tool that is simple, accurate and inexpensive there is only one, APK.

To make google happy and to stop them from lying about the safety of my website I’ve forced https re-direct on the RxKinetics website.

I’ve put it off because of the hassle it will cause every visitor here. And I resent the fact that google has taken control of the www.

Unfortunately your AutoUpdates may no longer work.

Older web browsers (prior to 2016) will see this site as broken because they do not support SNI.

Some links here may be broken.

I apologize for any inconvenience.

I’ve been a webmaster from the dawn of the internet, before google ever existed, they really need to be knocked off their high horse.

This update was long overdue. It has been nearly two years since the last significant update and a lot has changed since then. I’ve been on a sabbatical of sorts from programming since last summer when I retired from the full-time hospital pharmacy grind. I’ve spent the time since decompressing and mulling over what I could do to make the program more intuitive and relevant to current practices.

Targeted AUC dosing
I tried to make the biggest change as obvious as possible by replacing the (seldom used) DripCharts toolbar button with a Targeted AUC button:

After selecting and calculating a Vancomyicn model (either prospective or retrospective), the Targeted AUC button becomes active and when clicked, takes you to the AUC dosing dialog:

Targeted AUC dosing takes advantage of the fundamental relationship between clearance, dose and AUC that we all learned in basic pharmacokinetics class:

AUC = Dose (mg/hr) ÷ CL (L/hr)

Simply rearrange this equation to solve for dose:

Dose (mg/hr) = AUC x CL

Since dosing at the half-life is ideal for Vancomycin, the initial interval selected by AbPK is the estimated half-life plus the infusion time (rounded to the nearest whole number). The dose then is:

Dose (mg) = Dose (mg/hr) x Interval (hr).

The ideal interval and dose thus calculated are usually not practical, and are only meant to be a starting point. You must use your clinical judgment to select an appropriate dose to reach the target AUC.

Once a dose and interval are chosen, the AUC/MIC is calculated along with the expected peak and trough. Click the Save button to copy this information to the main program.

Copy consult to clipboard
In my opinion this is the second most important change in the latest version. We all work with the eMR now and it seems silly to still be printing hard copies of consults. This function will create a text summary of your pk consult and copy it to the Windows clipboard. You can then paste it into your eMR consult note by using the standard Windows paste shortcut: Ctrl+V.

Internet access
IS types are understandably paranoid about any application that accesses the internet. Disabling update checks on the settings dialog will disable all internet access by AbPK.

Sample time limits
Previous versions of AbPK had hard-coded stops on draw times, which I admit were short-sighted. Busy lab/nursing personnel don’t always draw serum levels at the optimal time. AbPK will now accept draw times that are outside the dosing interval.

Hints
Nothing new, but wanted to throw this out there. Please remember that hover hints are everywhere. Pause your mouse pointer for a second to see more details from the underlying information display. For example hover your mouse over the dose entry to view mg/kg. Pause your mouse over the Pk results frame to view time to steady-state. Hover your mouse over the serum level entry boxes to view more details. etc. etc.

Free as in beer
As always updates are free, downloaded from the web site using the web update function.

Sitting around the house all week with a nasty head cold and not feeling like doing anything physical gave me the opportunity to work on some things that I have put off for too long.

For any number of reasons the default population model may not fit a particular patient. If your patient has a documented history of vancomycin serum level analysis, you should use it. For new starts on patients with a history I usually click the retrospective tab to determine their model parameters. But, it has been on my TODO list for sometime to have this history available on the prospective tab. So this week I finally found the time to add a “Retrieve” button to the prospective tab.

If the patient has a history of serum level analysis, the “Retrieve” button is active, otherwise it is dithered out.

When the “Retrieve” button is active, click to select the most recent consult, regardless of drug. If you want to narrow your search to a specific drug, select a model first then click. The retrieve function will fill in the model parameters with the most recently calculated patient specific model. The date when that historical model was calculated is also displayed.

Hover the mouse anywhere over the ‘Edit model parameters’ frame to display more details about the historical model (weight, CrCl, measured trough, Kel, and Vd).

Click the “Restore” button to switch to the population model. You can use the “Retrieve” and “Restore” buttons to toggle back and forth between population and historical models for comparison.

If you decide to use the historical model the consult print-out will show that a historical model was used and the date from which it was pulled.

On the retrospective side I’ve added the option to choose the base model for Bayesian analysis. You can either use the population model or the historical model. Again, the date and details of the most recent analysis is displayed. Use this information to determine whether the patient history is applicable to the current situation.

Similar to prospective, you can use this dialog to toggle back and forth between population and historical models for comparison.

Also new, after you close the Bayesian results dialog you will see this informational dialog.

As the dialog states, the details of the Bayesian results have been automatically copied to the Windows clipboard. You can then use the Windows shortcut Ctrl+V to paste this information into your EMR consult or wherever you want to save it to.

My two cents

Of course, all of this, everything I have discussed above, depends on your fellow pharmacists following through, completing the job.

I harp on this all the time. If the level comes back within target range, don’t just write it down and go on, enter the level(s) and save the analysis!

So many opportunities are lost when someone doesn’t follow through. Not only with patient specific analysis as detailed above, but also with the population analysis tool (which I have discussed numerous times on this blog).