If one were to look past the mechanics and dig deeper into the mechanisms, Such as what Former_Chemist points out with respect to enteric coatings, they'll discover that it doesn't stop with the release of pfed, solely!
The aim of the medicine is to provide relief to cold and allergy sufferers.
In order for that to happen, it must be delivered to the blood stream.
The digestive system is a poor environment as it's aggresive.
The dissolution studies prove that not all of the medicine will withstand that aggresiveness so they develop delivery systems to compensate for the losses.
It's easy for most to associate the meanings of everyday teminology such as Extended Release, Sustained Release, and Controlled Release to mean essentially the same thing.
Make no mistake here or you'll bee barking up the wrong tree until these meanings take shape in the proper context.
I recently saw a post by Uncle Fester that demonstrates how easy it is arrive at that common misconception.
It dealt with suggesting that the 30mg and 60mg might not be subjected to the same types of delivery systems/inactives as their Longer acting cousins, 120mg and 240mg.
Not shooting the messenger here, just the message.
For example, The development of DryMatrix formulation was the first to cross over that line from being included in 120/240mg over to the faster acting immediate release 30/60's.
The DMF technology was developed for "Controlled Release" and employed in all strengths at one time, even redhots.
Controlled Release has little to do with Extended/Sustained Time Release technology developed solely for Longer Acting Meds. when it's being employed in fast acting meds.
Okay with that said....(and Ibee's no Doctor,so get your grains of salt out here
) let's look more at how the drug is delivered. Most meds must be broken down and delivered the bloodstream. The delivery system is engineered to provide max dosage for relief.
The aim of bees is to get all of the drug out of that finely engineered "Controlled Delivery" system all at once. And in one piece
When the delivery system is designed to work with natural digestive processes to control the release, it's unlikely that anybee will duplicate a synthetic environment similar to that of the humanbody to accomplish that same means to an end without substantial loss of the product. And without damage to the molecule.
They account for the losses incurred in the digestive tract in their dissolution testing and development. The maximum allowable without prescription in any medicine is based on that testing.
The act of the body breaking down the med for acceptance into the bloodsteam is the missing ingredient, IMHO, with respect to these types of approaches!
I could be wrong...
That's my take on duplicating the digestive actions in order to extract any main excipient from any pill.
It's info not meant to discourage, but to enlighten those that may not have considered this when trying to arrive at a solution.