# RxCalc — Pharmacokinetics for iOS

> Pharmacokinetic calculation tool for healthcare professionals on iOS. (iPhone/iPad app by Rob Fahrni.)

- Source: https://appshunter.io/ios/app/rxcalc/id321211290 (this page in markdown: same URL + `.md`)
- Developer: [Rob Fahrni](https://appshunter.io/developer/321211293)
- Category: Medical, Health & Fitness
- Price: $2.99
- Rating: 4.60/5 from 5 App Store ratings · 15 written reviews indexed
- Age rating: 12+
- Requires: iOS 15.0 · 1 MB
- Languages: American English
- Released: 2009-07-04
- Data updated: 2026-09-07
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/rxcalc/id321211290/reviews.md

## What is RxCalc?

RxCalc puts commonly used pharmacokinetic calculations in the palm of your hand with your iPhone or iPod Touch. The fast interface and comprehensive results help you spend less time crunching numbers and more time working on other, more important issues.

This tool is designed to help pharmacists, and physicians, quickly perform the most commonly used pharmacokinetic calculations. Calculations for designing new vancomycin and aminoglycoside dosing regimens as well as patient specific post-level adjustments to current dosing regimens are included.

## Key features

- Pharmacokinetic calculations
- Vancomycin dosing
- Aminoglycoside dosing
- Post-level adjustments
- Fast interface
- Comprehensive results

## Chart rankings

- #194 in Top Paid · Medical (US App Store)

## Recent user reviews (10 of 15)

All indexed reviews: https://appshunter.io/ios/app/rxcalc/id321211290/reviews.md

### 5/5 — Use this Almost Every Day

*2017-12-11*

This app is very useful for the clinical pharmacist responsible for kinetic dosing.  It is quick, simple to use and works well. Have found this provides more accurate predictions for geriatric patients, in comparison to other kinetics calculators tried in the past.

### 5/5 — Love it

*2017-03-19*

I like this app it's simple and to the points. Pretty handy when your on the floor. You don't have too many options to confuse you but you can still adjust VD to your liking. I'm surprised this app is not reviewed or used that much.

### 5/5 — Very helpful

*2016-01-31*

This has been the most useful app for doing pharmacokinetics that I found. It does the calculations for aminoglycosides, vancomycin and high dose extended interval dosing. I have been using it for over five years. It's efficient, no frills interface is quick  and can save a lot of time. Highly recommended!

### 3/5 — OK but needs work

*2012-06-24*

There is no report feature. At least condense the results and relevant data on a single screen that can be air-printed or sent to the device camera roll. As others noted, there are slim pickings for iPhone kinetics apps. This app is a worthy effort but it needs some improvement.

### 1/5 — RxCalc

*2011-05-29*

I have been a clinical pharmacist for 19-years.  For the last 8-10 years, I have been using ClinRx on my palm.  Unfortunately, ClinRx is not available for I-Pod/I-Phone.  I misplaced my palm and was looking for an alternate program.  I had seen a review from a professor at UC San Francisco praising RxCalc.  I purchased this program based on that review.  I found it less than useless.  I plugged in the data for a large, relatively young patient with a high vancomycin trough.  The data for the single level vancomycin trough provided data that was completely inaccurate.  I tried again with similar data.  Again, the resultant data was exactly opposite of what someone who is familiar with pharmacokinetics would expect.  Example:  1500mg every 8 hours with a reported trough of 28 at 1/2 hour prior to next dose in a 128kg patient recommends a NEW dose of 1750mg every 8 hours for a goal trough of 18.  If the trough is already higher than desired, why would you want to increase the dose?  The original data on an actual patient provided a Tau of approximately 3 hours when the actual Tau should have been 12-18 hours.

I would not recommend this program, especially if the person purchasing the program does not have enough experience to recognize when the data being provided is not accurate.

**Developer response:** Hello. We finally have the ability to reply to our reviews and I'd love to hear any feedback you would like to provide. Do you happen to know the model ClinRx is using? RxCalc is based on the Creighton model. There are many to choose from and we'd love to know the model you prefer. Please send any feedback you'd like to provide to support@applecorelabs.com. Thanks for taking the time to write a review.

### 3/5 — its ok

*2011-01-11*

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.

**Developer response:** Hello. RxCalc is based on the Creighton model. There are many to choose from and we'd love to know the model you prefer. Please send any feedback you'd like to provide to support@applecorelabs.com. We love hearing from users of RxCalc. Thanks for taking the time to write a review.

### 5/5 — RxCalc is Quite Useful

*2010-09-05*

As already mentioned, there may be some underdosing initially.  Perhaps, one tends to expect too much when the equations predict a serum level of 13.7 mcg/ml and then the actual measured level turns out to be ONLY 12.1 mcg/ml and, therefore, is incorrect!.   Mathematical equations, by their nature, are very exact.  Yet they are applied in the same manner to the many differences among our patients.  When I use any pharmacokinetic dosing model in an empirical fashion I am simply looking to be in the correct ball park once I have an actual level with which to work.  RxCalc helps me do this without spending a lot of time and effort coming up with a regimen that will most likely be changed after the first serum level is measured and reported.  Not having many options is no reason not to use RxCalc.  This is an iPhone app after all, not software to run on the hospital's mainframe!  However, I am disappointed that when adjusting dosing based on measured levels I must have both a peak and a trough.  Most of the time I only have a trough and am unable to use RxCalc to assist in adjusting the dosing.  I have been assured by Apple Core Labs that making the entry of a peak level optional is currently being tested and should be expected in the next RxCalc release. 

Robert Martin, PharmD

### 1/5 — Needs transparency

*2010-09-03*

Like others I found this program to significantly underdose patients. The Ke value calculated to about half that of accepted methods. The equation for Ke should be made transparent. The program should also offer multiple methods of kinetic dosing.

### 1/5 — Severely underdoses!!

*2010-08-16*

This program really underdoses all my patients. It predicts troughs of 20 and 25 with normal doses. I used it just the other day and it predicted a trough of 26.4 and I got an actual trough of 14.7--no changes clinically with the patient. This program is crap. Good thing it only cost 99 cents!

### 1/5 — Garbage

*2010-02-26*

Does not work. Interface is clunky and gives me error messages when I put in values. I don't believe for a minute the positive reviews are real. Cannot use product nor would you want to trust calculations (if you can get them from the app!) in a clinical setting. If it smells like garbage, works like garbage, and looks like garbage, it probably is.

## Frequently asked questions about RxCalc

### What is RxCalc used for?

RxCalc is a medical application designed to perform commonly used pharmacokinetic calculations. It assists pharmacists and physicians in designing new dosing regimens and making patient-specific adjustments for medications.

### What specific calculations does RxCalc offer?

RxCalc includes calculations for designing new vancomycin and aminoglycoside dosing regimens, as well as patient-specific post-level adjustments to current dosing regimens.

### What devices is RxCalc compatible with?

RxCalc is designed for iPhone and iPod Touch devices.

### How much does RxCalc cost?

RxCalc is a paid application, available for a one-time purchase of $2.99.

### When was RxCalc last updated?

The latest version of RxCalc was released on April 17, 2024, indicating ongoing support and potential improvements.

### What is the user rating for RxCalc?

RxCalc has received a high rating of 4.6 stars based on 5 user reviews, suggesting positive user satisfaction.

### What is the age rating for RxCalc?

RxCalc has an age rating of 12+, making it suitable for a broad range of users.

### Does RxCalc have ads?

No, RxCalc does not contain advertisements, providing an uninterrupted user experience.

## Version history (last 5 releases)

### 1.6 — 2024-04-17

Set minimum iOS version to 15.0

### 1.5 — 2020-06-30

Requires iOS 13
Supports Dark Mode

### 1.4 — 2017-09-22

Updated to support iOS 11

### 1.3 — 2015-09-26

Compatible with iOS 9
Uses numeric keypad for data entry

If you like RxCalc, please take a moment to leave a review, it really helps! If not, please send your feedback to support@applecorelabs.com or visit http://applecorelabs.com/contact/ for help.

### 1.2.1 — 2012-11-22

1. iPhone 5 bug fixes
2. Requires iOS 5 or newer

Plus all this...
1. Support for dosing adjustment using single level vancomycin kinetics 
a. 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 
b. Calculations for gentamicin and tobramycin are based on 7mg/kg adjusted body weight 
c. Calculations for amikacin are based on 15mg/kg adjusted body weight 

RxCalc formula/models: 
1. Industry standards for ideal body weight (IBW) calculations 
2. Cockcroft-Gault equation for creatinine clearance calculations 
3. Vancomycin utilizes the Creighton model for calculations: 
a. Kel = 0.0044 + (CrCl x 0.00083) 
b. Vd = 0.7 L/kg (using actual patient body weight) 
c. Vancomycin Vd is adjustable based on user need between 0.5 L/kg and 1 L/kg (default 0.7 L/kg) 
4. Aminoglycoside model utilizes the following: 
a. Kel = (0.14 + (0.00293 * CrCl) 
b. Vd 0.26 L/kg (using adjusted patient body weight) 
a. Aminoglycoside Vd is adjustable based on user need between 0.2 L/kg and 0.5 L/kg (default 0.26 L/kg) 
b. Adjusted body weight for aminoglycoside calculations is calculated as follows: IBW + ((ActBW - IBW) x 0.4)

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## More apps by Rob Fahrni

- [Stream - A Feed Reader](https://appshunter.io/ios/app/stream-a-feed-reader/id1377383950)

All apps by Rob Fahrni: https://appshunter.io/developer/321211293

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-07.*