Antibiotic Kinetics© support FAQ's
FAQ is an acronym for Frequently Asked Question. This page is intended to provide answers to common questions, along with some useful tips and tricks that are presented as questions.
  1. General questions
  2. PDA problem solutions
  3. Android specific problem solutions
  4. Palm specific problem solutions
  5. Windows Mobile specific problem solutions

General questions
Q. Why are there two Vancomycin models in the program?
A. Vancomycin is a difficult drug to dose because of extreme inter-patient variability of pk parameters. No single model will fit all patient populations.
  • The CL model calculates a clearance and was derived from the work of Winter.
  • The Kel model calculates an elimination rate constant (Kel), and was derived from the works of Matzke.

Please bear in mind that vancomycin is not a very predictable drug, and these models will not fit all patient populations. It is important to save your data, and to periodically re-analyze your population parameters vs outcome.

A word of advice: don't hang your "PK hat" on your ability to predict vanco levels. I've been looking for twenty years and have yet to find a method or model that accurately predict vancomycin levels in all patients.

Q. How do I adjust a dose based only on a trough level?
A. You may analyze a single trough, a single peak, or a random level drawn at any point within the dosing interval by selecting the single point Bayesian method. On the Hand-held versions of Antibiotic Kinetics©, this method is designated by the abbreviation "B".

The serum level time is relative to the preceeding dose. If, for example:

  • Vancomycin Q 12 hours
  • Infused over one hour
  • Trough level drawn 30 minutes before the dose

The timing of the trough level is therefore 10.5 hours after the end of the infusion.

One way to grasp this concept is to understand that the serum level is the result of a dose which has been given, not from a future dose.

Q. Why does the creatinine clearance from the Antibiotic Kinetics© program differ from what I calculate by hand?
A. The difference is most likely due to the weight that you are using in your hand calculation. Because creatinine is produced by muscle tissue, C&G recommend that you use lean body weight, except in morbidly obese patients. Because creatinine is produced by muscle tissue, not fat, additional weight in form of fat does not significantly alter the production of creatinine.

There is considerable difference of opinion among practitioners concerning the most appropriate creatinine clearance equation to use. Antibiotic Kinetics© includes multiple creatinine clearance methods from which to choose. Use the method which is most appropriate for your patient. Please refer to this page for more information on creatinine clearance calculations: Dosing of renally excreted drugs

Q. How do I dose IM gentamicin?
A. Enter an infusion length of 90 minutes, which is the average time for IM absorption of aminoglycosides. Be sure to draw your peaks at least 90 plus 15 minutes after the injection.
Q. Must I always use steady-state analysis? For example, my patient received 2 doses of 1gm vanco q12hr, and for some reason the dose was decreased to 600mg around which levels were drawn.
A. You do not have to assume steady-state if you use the 3-point method. Draw a trough before the 600mg dose, a peak after, then a mid-point level after that. The program will use the pre-dose trough and the peak level to calculate the volume of distribution. The two post-dose levels are used to calculate the elimination rate.
Q. Why is the default dose for once-a-day gentamicin 5mg/kg instead of Hartford's 7mg/kg?
A. Please refer to this consensus document which appeared in the June 1997 issue of the International J. of Clinical Pharmacology and Therapeutics:

In many respects the approach of the Hartford nomogram is just as simplistic as giving 80mg Q 8 hours to all patients with a "normal" serum creatinine. Instead, all patients should be individually dosed in order to maximize therapeutic efficacy and minimize the risk of toxicity. The patient should receive a large enough dose to produce a peak level that is 8 to 10 times greater than the MIC. The dosing interval should then be extended to produce a trough less than 0.5 mcg/ml in order to provide a washout of aminoglycoside in the renal tubule thereby reducing toxicity.

Q. During prospective dosing of pediatric patients there seems to be no way to chose an initial target peak/trough value like there is for adults.
A. The initial pediatric calculations are weight based, as they are in every pediatric reference book you will find. Although you cannot target a specific peak and trough, the program will show estimated peak and trough levels from your selected dose.

The reason that initial doses are weight-based is because the creatinine clearance equations for peds are not accurate enough to be used for pk modeling.

Q. Do I enter serum level times relative to the beginning or the end of the infusion?
A. Times are relative the beginning and the end of the infusion.
  • For pre-dose times, this refers to the beginning of the infusion, hence the instruction "minutes BEFORE infusion".
  • For post-dose times, this refers to the end of the infusion, hence the instruction "hours AFTER infusion".
Q. How does the program handle late doses?
A. Unfortunately, late doses can not be avoided, so how can you use these levels? There are at least two late dose scenarios, each would be handled differently, depending on the methodology you are using.

The first late dose scenario we'll describe occurs if the dose was late but the levels were correctly drawn relative to the actual hang time. For example, the nurse is supposed to be giving gent 80mg Q 8 hours, at 6-14-20, but the sample dose is given late, at 1600. The trough was drawn at 1530 and the peak at 1730. As you can see, the levels are correctly drawn relative to the late dose.

First, let's examine the Sawchuk and Zaske method. This method is the gold standard for evaluation of peak and trough levels in the one-compartment open model. Sawchuk and Zaske drew three levels: a trough before the dose, a peak after the dose, and another trough after the dose. However, many institutions take a shortcut and only draw two levels, a trough before the dose and a peak after. If the patient is at steady-state, then you can assume that the second trough after the dose will be the same as the trough before the dose. Under most circumstances, this is a valid assumption and will save laboratory expenses.

Next, look at Sawchuk and Zaske's equations for calculating pk parameters, you can find them in the program help file (Press the F1 key). Where is the dosing interval in these equations? ...... nowhere! The dosing interval is not used in any calculation.

If you are using the 3-point method, the interval is not used, and it doesn't matter if the dose was given late, as long as the levels are correctly drawn, relative to the time the dose was actually given.

If you are using the two point method, the dosing interval is only used to extrapolate the pre-dose trough to simulate the after-dose trough. Therefore, in the Antibiotic Kinetics program, instead of entering the "ordered" interval, you would enter the time between the last dose and the sample dose. Using our same example, if the nurse is supposed to be giving gent 80mg Q 8 hours, at 6-14-20, but the sample dose is given late, at 1600. In the Antibiotic Kinetics program you would enter an interval of 10 hours. Again, this is because the interval is only used to extrapolate the pre-dose trough.

The second late dose scenario occurs when the dose is give late and the levels are correctly drawn relative to the scheduled hang time, not the actual hang time. For example, if the nurse is supposed to be giving gent 80mg Q 8 hours, at 6-14-20, the sample dose is given late, at 1600, but the trough was drawn at 1330 and the peak at 1530. As you can see the levels are correctly drawn relative to the scheduled dose, not the actual hang time, the "peak" is not a peak at all, but a trough drawn before the dose was given.

This scenario is the result of a lack of communication between lab and nursing. In this case, throw out the peak and just use the trough. With Bayesian you only need a single trough level.

The Antibiotic Kinetics program is deceptively simple in this area. When you hit a snag like this, you have to stop and think, and that's the downside to having such a simple interface for entering levels. The other alternative, and the one taken by most other PK programs, is to have you enter each and every dose and the time each dose was administered. This approach punishes you each time you have to enter a simple set of levels. The Antibiotic Kinetics program only makes you work hard in a problem situation.

Q. How do I enter my own drug model?
A. The model editor is accessed from the program menu:

Windows CE

  • Tap Edit on the MenuBar
  • Tap Models
  • Tap the [+] button to create a new blank model
  • Or tap the [cc] button to copy from the current model

Palm OS

  • Tap Go To on the upper right of the main screen
  • Tap Models
  • Tap the (+) button to create a new blank model
Q. Where I can find linear regression equations for beta-lactam antibiotics? I'd like to be able to get a good set of Kel values to plug in for cephalosporins and penicillins.
A. Unfortunately, this information is not found in one single reference. Bennett's Drug Prescribing in Renal Failure and Chernow's Critical Care Pharmacotherapy have tables of pk data for common drugs. The FDA package insert of newer drugs usually has an excellent pharmacokinetics section.

For a detailed tutorial on creating one compartment models, please see this page:

I have compiled the pk parameters of some common antibiotics into a table on this page:

Q. My patient is a double amputee, the program won't let me enter his height (36"), what should I do?
A. The program does not make any specific adjustments for amputees, so you'll need to do some calculations the old-fashioned way. Enter the patient's pre-amputation height. The program will calculate a baseline lean body weight.

Because creatinine is produced by lean tissue, to get a more accurate estimate of CrCl, you'll need to estimate post-amputation muscle mass. Start with the LBW calculated from the patient's pre-amputation height. Then deduct a percentage depending on the extent of the amputation:

  • Hand - Decrease LBW by 0.7%
  • Forearm and hand - Decrease LBW by 2.3%
  • Total arm - Decrease LBW by 4.9%
  • Foot - Decrease LBW by 1.5%
  • Calf and foot - Decrease LBW by 5.8%
  • Total leg - Decrease LBW by 16%

In this case, since your patient is a double amputee, you would decrease the LBW by 32%. Let's call this the Amputee-Adjusted LBW (AALBW).

If the patient's actual weight is less than the AALBW, then the patient is underweight and you should use the patient's current weight to calculate CrCl.

If the patient weighs more than the AALBW, then you should hand calculate the CrCl using the AALBW.

Q. My patient is bedridden and I cannot obtain his/her height, what should I do?
A. Good question. A patient may also have scoliosis or severe contractions that prevent a true height measurement. There are (at least) three methods that may be used to estimate height when actual measurement is not possible: knee height, forearm length and demi-span. Estimating height in bedridden patients
Q. Does Antibiotic Kinetics interface with our Pharmacy Information System?
A. Antibiotic Kinetics© may be interfaced with a PIS, using our open interface specification. Please contact your PIS vendor to request implementation. RxKinetics software interface specs
Q. Does Antibiotic Kinetics run on a Macintosh computer?
A. We do not currently offer a native Mac version of Antibiotic Kinetics (a Mac version is currently in development). However, people have claimed that Antibiotic Kinetics runs properly on a Mac if used in conjunction with Windows emulation software, such as Virtual PC.

PDA problem solutions
Q. The serial number you sent me doesn't work!
A. Your serial number is calculated specifically for your PDA, based on the information you provide us.

The serial number for the Palm version is tied to your device HotSync ID, which is displayed on the program registration screen as "User name".

The serial number for the PocketPC version is tied to your device owner name, which is displayed on the program registration screen as "User name".

You must supply these names exactly as they appears on this screen. Case, spaces and punctuation are all relevant. We will gladly re-calculate your serial number with the correct information, just ask!

Q. What is the serial number to download the update?
A. No serial number is necessary to download Antibiotic Kinetics.

Palm OS problem solutions
Q. Why does the Palm version run so slow?
A. Yes, the Palm version runs slow on older, inexpensive devices like the Visor Deluxe or the Palm M105. These cheaper Palm devices use a very slow processor (Motorola Dragonball), which works fine for keeping track of appointments, but is slow when performing complex math functions.

I have used a speed hack called "AfterBurner" with these slow old Palms (available from PalmGear). The speed difference is noticeable, but not dramatic. Otherwise, if you have the need for speed, buy a new Tungsten, they scream.

Q. AbPK for Palm OS has become unregistered!
A. You may have inadvertently changed your device indentification. Your registration code is specifically tied to your Palm HotSync ID. Therefore, if you change the device ID, you will need to get a new registration code.

You may request a new code from RxKinetics by sending an email with your old user name and your new user name (include as much information as possible for fastest processing -please provide your original order number to speed up the process).

Another simple solution is to just reset your Palm HotSync ID back to its original value. The following procedure will allow you to change your HotSync ID without affecting anything you have installed on your Palm device:

  1. Run the Palm Desktop application
  2. Select USERS from the TOOLS menu
  3. Click on your HotSyncID in the list to select it
  4. Click the RENAME button.
  5. Type in your new/correct HotSyncID now very carefully
  6. Click OK to return to the USERS Dialog
  7. Click OK to exit out of the USERS Dialog
  8. Exit out of the Palm Desktop Application
  9. Do a regular HotSync - this will copy your corrected name down to your Palm device.

You will now be able to use your original registration code.

Q. I replaced my Palm, will you give me a new registration code?
A. You may request a new code from RxKinetics by sending an email with your old user name and your new user name (include as much information as possible for fastest processing -please provide your original order number to speed up the process).

However, my advice to users replacing their Palm is to keep the same HotSync ID. When you use the same ID, HotSync will automatically transfer all your data (calendar, contacts, etc) AND all your software to your new Palm.

The following procedure will allow you to change your HotSync ID:

  1. Run the Palm Desktop application
  2. Select USERS from the TOOLS menu
  3. Click on your HotSyncID in the list to select it
  4. Click the RENAME button.
  5. Type in your new/correct HotSyncID now very carefully
  6. Click OK to return to the USERS Dialog
  7. Click OK to exit out of the USERS Dialog
  8. Exit out of the Palm Desktop Application
  9. Do a regular HotSync - this will copy your corrected name down to your Palm device.

You will now be able to use your original registration code.

Q. I replaced my Palm OS PDA with a Treo (Windows Mobile Smart Phone), will you give me a new registration code?
A. Installing the program StyleTap on your new device will allow you to run Antibiotic Kinetics© for Palm.

StyleTap allows you to set the User Name (HotSync ID) for your new device to the value that you used to register on your Palm OS device. Hence, no new registration number is needed.

Although the price is a little steep ($49.95), consider that StyleTap give you access to the thousands of applications that have been developed for the Palm platform over the past ten years.

Windows Mobile problem solutions
Q. AbPK for PocketPC has become unregistered!
A. You may have inadvertently changed your device indentification. Your registration code is specifically tied to your device owner name. Therefore, if you change the device ID, you will need to get a new registration code.

You may request a new code from RxKinetics by sending an email with your old user name and your new user name (include as much information as possible for fastest processing -please provide your original order number to speed up the process).

Another simple solution is to just reset your device owner name back to its original value. The following procedure will allow you to change your device owner name without affecting anything you have installed on your PDA:

  1. Tap "Start" then tap "Today"
  2. Tap the word "Owner" on your PDA
  3. Correct the Name
  4. Tap "OK"

You will now be able to use your original registration code.

Q. I replaced my Pocket PC, will you give me a new registration code?
A. You may request a new code from RxKinetics by sending an email with your old user name and your new user name (include as much information as possible for fastest processing -please provide your original order number to speed up the process).

However, my advice to users replacing their PDA is to keep the same device owner name used on the old PDA.

The following procedure will allow you to change your device owner name:

  1. Tap "Start" then tap "Today"
  2. Tap the word "Owner" on your PDA
  3. Correct the Name
  4. Tap "OK"

You will now be able to use your original registration code.

Q. The program doesn't run on my fancy new Pocket PC 2003 or Windows Mobile 5.0 PDA.
A. Please download version 2.x which runs under Microsoft's .NET Compact Framework.
Q. When I install AbPK on my new Windows Mobile 5.0 PDA it gives an "error" message.
A. While installing AbPK on Windows Mobile 5.0 you may see a message on your PDA stating 'This program is from an unknown publisher. You should install it only if you trust its publisher.' This message simply means that I have not paid extortion money to Microsoft. Tap YES to install AbPK.
Q. I can't see the entire screen when I install AbPK on my new Treo.
A. This issue has been resolved with version 2.x which has been developed expecially for the square form factor found on these devices.
Q. I am getting a 'File pointer has reached end of file' error on my PocketPC.
A. One of the database files has become corrupted. To fix the error, exit AbPK and erase the data files, they will be re-created when you re-start AbPK.
  1. Exit out of AbPK.
  2. Tap "Start", then "Programs" then "File Explorer"
  3. Navigate to \Program Files\Antibiotic Kinetics
  4. Tap and hold on the file "abpk_patient" then Tap "Delete"
  5. Tap and hold on the file "abpkmodels" then Tap "Delete"
Q. There appear to be multiple copies of AbPK running on my Windows Mobile 5.0 PDA.
A. This issue has been resolved with version 2.x which runs under Microsoft's .NET Compact Framework.
Q. When I run AbPK on my iPAQ 2795 I get an application error "cannot find extension file pvbDecl.dll".
A. We are finding many issues with Windows Mobile 5.0 devices. Even Microsoft's own Reader program does not run. To solve this problem, you may need to download and install the latest Firmware update from HP's support site.

Android problem solutions
Q. When I tap on the AbPK icon on the home screen, it takes me to the main screen.
A. To switch between tasks on Android, perform a long press on the Home button, the task switcher will appear.

Tap on the AbPK icon in the task switcher to go back to where you left off.

Q. The screen does not rotate when I slide out the keyboard on my Motorola Droid.
A. Yes, all screens, except the graph, are currently fixed in portrait mode. The GUI portion of Android SDK is overly complex, every widget has to be hand-coded. I haven't had the time yet to redraw every screen for a landscape rotation, that will come in future versions. Please use the app in portrait mode. To edit a field, tap it and the software keyboard will popup. It's not a bug, it's a feature!
Q. Sometimes when I rotate the phone from horizontal to vertical and visa versa, the program goes back to opening screen. Nothing is lost, it just shows the opening screen again.
A. This is called a "nag" screen, you do not see this in the paid version. The purpose of a "nag" screen is to irritate you, and motivate you to purchase the paid version. I've spent six months of my life, working 10 hours a day to get this application out there. I don't think anybody works for free, do you? If you are using the app, please support my programming efforts. Your conscience and I will thank you.

[ Return to RxKinetics Home ]

©Copyright 1984 - 2011, RxKinetics. All rights reserved