Infusion, for the time being, will not be updated. Apple has a number of rules to help maintain the app store quality. Unfortunately some of them are very vague, or are broadly applied, making unjust app store rejections a recurrent problem.
For Infusion the rule in question it's 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.
It was my understanding that Infusion wouldn't cross this rule because the user had already chosen the dosage of the drugs, so it was never calculated by the app. Unfortunately a reviewer and, later, a review board judged otherwise.
Besides giving the app to a "institution", the only way to approval offered was to drop the option to provide the dosage of a drug indexed to weight and only let the user choose the full mass of those drug for the calculation (it seemed that the issue to them was the multiplication of the dosage by the patiente weight...). This seemed to show a lack of understanding for the issue in hand. I tried to reason, showing that we prescribe drugs like this for good reason and their proposal was really dangerous if I allowed it (and if we did it in medical practice). To make my point, as they aren't health care professionals, I showed them excerpts of pharma books were the dosage it's chosen like this.
After this the only significant reply was that I couldn’t never have the app approved outside the "institution" solution.
This type of issues have already been tackled by the FDA. They were worried that some apps could function as medical devices, that should be regulated by them.
But they also acknowledged that for some apps this could be extreme, for their simplicity. They called those "Mobile Apps for which FDA intends to exercise enforcement discretion (meaning that FDA does not intend to enforce requirements under the FD&C Act)"
One type of apps on that group it's the ones that "Automate simple tasks for health care providers". As an example they give:
Mobile apps that perform simple calculations routinely used in clinical practice – These are apps that are intended to provide a convenient way for clinicians to perform various simple medical calculations taught in medical schools30 and are routinely used in clinical practice. These apps are generally tailored for clinical use, but retain functionality that is similar to simple general purpose tools such as paper charts, spread sheets, timers or generic mathematical calculators.
30 The types of information in these calculators are available in medical sources which includes medical textbooks used in the curriculum of accredited medical schools.
The types of calculations done by Infusion are taught in medical schools. High school students can even do them if they know the units (in contrast, ask them to calculate a Glasgow Coma Scale without notes).
I also informed the review board of this guidance, but it wasn't enough for app approval.
Without more options I will not try to update Infusion anymore. In this way the app store will slowly turning into a wasteland of this type of apps.