Who Can Write a Drug Dosage Calculator?

Several years ago I had an idea for a smartphone app that could be used to calculate doses for drugs that are prescribed frequently to patients with heart rhythm problems. These drugs include antiarrhythmics such as dofetilide and sotalol, and the new oral anticoagulants such as dabigatran and rivaroxaban. These drugs are handled by the kidneys, and dosage is dependent on kidney function. The package inserts for these drugs advise the correct drug doses based on the calculated creatinine clearance, a formula that involves the patient’s weight, age, sex and serum creatinine. Once the creatinine clearance is calculated, a lookup table is used to determine the dose. For example, here is the rivaroxaban dosing information:


Medical calculator apps are common and invariably include a creatinine clearance calculator. The problem I had was trying to remember all the different creatinine clearance cutoffs for each dose of each drug. This seemed like perfect job for an app. Just fill in the information needed to calculate the creatinine clearance and have the app figure out the creatinine clearance and look up the dose. Thus my app EP Mobile was born. Over the years I have added many more modules to the app, including everything from algorithms localizing accessory pathways to entrainment mapping, but the original concept was to provide the drug dose calculators which remain a key part of the app.

Or maybe not. I routinely update the app, and submitted an update a week ago to Apple (not related to the drug dose calculators). For the first time ever I received a rejection from Apple. They quoted this from their App Store Submission Guidelines:

22.9 Apps that calculate medicinal dosages must be submitted by the manufacturer of those medications or recognized institutions such as hospitals, insurance companies, and universities

Attached were screenshots of the offending calculators:

A drug dose calculator
A drug dose calculator

I am a physician. Part of my job is to calculate medicinal dosages, as the legalese above terms it. This is not the job of hospitals, insurance companies, or universities. Ultimately I as a physician am legally responsible for calculating correct dosages. Yet somehow physicians are left off the list of those qualified to submit apps that calculate drug dosages. The development of an app that simply does what the drug package insert instructs the physician to do in order to calculate a drug dosage, but in an easier manner, should not be restricted to drug companies, hospitals, insurance companies (insurance companies?) or universities. The few of us physicians who are also app developers are certainly in as good a position as any of these other parties to develop apps like this. The algorithms to calculate these doses are extremely simple.  As my app is open-source, the source code is freely available for anyone to inspect to make sure the calculations are coded properly.

I appealed this decision to Apple and I hope they reconsider. I doubt they will. I see the handiwork of Apple’s legal department here. Don’t trust physicians to figure out what tools are useful on their own. Far better to let them go back to carrying around a bunch of drug company propaganda plastic rulers and let them do those creatinine clearance calculations by hand, using long division. Just like back in the good old days.

By mannd

I am a retired cardiac electrophysiologist who has worked both in private practice in Louisville, Kentucky and as a Professor of Medicine at the University of Colorado in Denver. I am interested not only in medicine, but also in computer programming, music, science fiction, fantasy, 30s pulp literature, and a whole lot more.


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