The cool engineering behind Xeljanz XR

My doctor mentioned this, and the engineer in me thought it was extremely cool. So here’s how they got Xeljanz XR to work properly, so that it’s a once-daily pill instead of twice-daily: they coated it and put a hole in the end!

What is Xeljanz?

Xeljanz XR (for “extended release”) is a once-daily pill used to treat rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. It’s also being tested for ankylosing spondylitis currently. You may know it from its aggressive marketing campaign. The makers are really pushing the fact that it’s a pill, not an injection like many other similarly effective arthritis medications (biologics).

Though not technically a biologic medication, it works in a similar fashion by inhibiting inflammation to control autoimmune conditions. To be a biologic medication, like Humira or Enbrel, a drug has to come from a biologic source. Because of this, they usually have to be refrigerated and injected for them to work properly. In contrast, Xeljanz has a simpler chemical structure that doesn’t require biologic material to create. (For more about what makes a biologic a biologic, check out my other post.)

A biologic-like drug without the injections? Exciting!

Xeljanz comes in three forms: a 5mg immediate release pill, a 10mg immediate release pill, and an 11mg extended release pill. For arthritis patients, the dosage for Xeljanz (immediate release) is 5mg twice a day. This is important to keep the proper amount of the drug in the body for long enough. It only takes 3 hours for your body to remove half the Xeljanz from your system, so simply taking more at once wouldn’t solve the problem and make it last longer. (The 10mg dosage is for ulcerative colitis patients.)

It’s easier for everyone if patients only have to take one pill per day instead of two, but that leaves engineers with a problem. The medicine has to stay in the body in the right amount for longer, so how will that be done?

How does the “extended release” work?

From what I can tell, Xeljanz XR uses a sustained release mechanism called an osmotic pump. There are a number of different ways engineers get medicine to release over a longer period of time, but I think this one is especially cool. The medicine itself is wrapped inside a coating that isn’t broken down by the body. This keeps the medicine from being absorbed by the body all at once, like in the immediate release Xeljanz. This coating has small pores in it, though, that are designed to only let water through.

While the pill travels through the body, water passes through the coating to mix with the medicine inside. Once the water mixes with the medicine, though, the mixture can’t get back out through the coating’s pores. Having the extra water inside the pill means that the pressure is higher inside, so the pressure needs somewhere to release. Each pill contains a hole in one end, so that the pressure from the water forces the medicine out of that hole. The medicine is released slowly as water passes through the pill’s coating and pumps it out the hole, giving it the sustained release. It’s a mini pump that you can swallow, and water does all the work!

Long story short: to make the medicine take longer to release, engineers wrapped it in a coating that can’t be broken down by the body. They drilled a hole through the coating in one end, though, so the medicine slowly leaves through there after you swallow the pill.

Because the coating on the pill can’t be digested by the body (a necessary feature), the coatings pass through completely… and may be seen later. That’s normal and not harmful. This also means you can’t cut these pills, though, because then they won’t work correctly. Instead of slowly being pumped out, the medicine would quickly be absorbed if the pill were cut in half and the protective coating broken.

The patent I found for the “sustained release dosage form” of Xeljanz is really a laundry list of mechanisms that use the same type of coating that doesn’t break down in the body, from what I can tell. It does describe the osmotic pump among the methods (they were really leaving all options open). Admittedly, I didn’t read the whole thing all the way through, although you can if you want. If you can make it through that, you have a great career ahead of you as a patent lawyer! (Good luck.)

I hope you found my explanation interesting and not too hard to get through! I didn’t know about osmotic pumps before I started researching this, but it’s a pretty ingenious way to control how medicine is released. It’s so simple, and so effective!

-Bri

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