Eli5 how come we can have transdermal patches and implants that last for months for things like birth control but not for other drugs

Question

I’m thinking things like levothyroxine that people have to take every day and are really important not to miss. Why can’t we have an implant or patch for this? It would be really helpful and possibly save lives.

In: 16

Answer 1

Nobody is developing that for you because they know the following:

Levothyroxine (LT4) is very sensitive, unstable material. It would probably not stay active in a patch.

LT4 monthly dose is about 4000 milligrams for an average person. A patch usually can hold a few milligrams of substance. A birth control patch has less than 1 milligram in it, a nicotine patch is about 25. So the patch capacity is way too low.

Skin patches work well with hydrophobic substances, aka things that dissolve in oil but not in water. Nicotine and estradiol are such, LT4 is the opposite.

But there are actual efforts to develop improved LT4 delivery methods, so hopefully you will get something better. Unfortunately, as I said, LT4 is complicated.