Enteric Coated

14Feb/11Off

Enteric Coated

Is there a difference between enteric coated aspirin and buffered aspirin?

There is a difference; as the first respondent said, buffered aspirin contains a base to neutralize some of the acid (a buffer), while enteric coated aspirin has a special coating that won't release the drug until it reaches the intestine. However, there is a very crucial (and common) misconception in his explanation - neither enteric coating nor buffering do *anything* at all to reduce the damaging effect that aspirin has on the stomach. Yes, aspirin is an acid, but it is a weak acid (pKa around 3 or so, I believe) - the HCl in your stomach is much, much stronger (pH of around 1) and the aspirin won't do anything to make it worse with direct acidity. Instead, the damaging effects come because it is a COX inhibitor (as are other NSAIDS, such as ibuprofen or naproxen), which means it inhibits prostaglandin synthesis. Prostaglandins are one of the key protective mechanisms for the GI mucosa, and without them, it is more prone to damage. Ironically, what enteric coating or buffering does is to decrease the effectiveness of aspirin absorption - drugs must be in an non-ionized form in order to be absorbed through cell membranes - as a weak acid, aspirin would be non-ionized in the acidic environment of the stomach; the enteric coating would change the site of absorption to the intestines, which are slightly alkaline, which would protonate (ionize) the aspirin, and inhibit absorption. Likewise, having a buffer would alkalinize the local environment, decreasing absorption. So, both of these are really just marketing techniques when they say they "protect" the stomach - there is just no way to do this with any coatings, given aspirin's inherent properties.

Edit: To respond to the above - I meant no personal offense to your original response; I don't mean to use this as a forum for debate of original research, so I will preface this that we agree on the main point, which is that there is a difference between the two formulations. However, for completeness' sake, I will point out that more recent research has suggested that with chronic aspirin therapy (as opposed to short-term, as was the case in the study you presented), the benefits of enteric coating decrease, which might suggest that in the long term, PGE2 inhibitory effects of aspirin itself override the local effects of the specific formulation. In addition, there is ongoing study about the effects of the coating themselves on the efficacy of the drug (possibly due to some of the pharmacokinetic considerations pointed out above). I have included some examples with full-text available below. I will disclaim that I have no first-hand experience with research in this area, and I could supply just as many sources that support what you said (it's all in what you select...) - however, I do feel that it is responsible to point out that it is an area of active study, so I don't think either of us can claim to be completely correct as a result.

http://www.ncbi.nlm.nih.gov/pubmed/17669925

http://www.ncbi.nlm.nih.gov/pubmed/15068408

http://www.ncbi.nlm.nih.gov/pubmed/18160364

http://www.ncbi.nlm.nih.gov/pubmed/16950199