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

It is a big thing that the dynamics of the medication need to be preserved. So some medications have certain enzymes or chemicals they have to come in contact to cause a shape or chemical change to make them active in the right place at the right time. If they do not come in contact they may not work or that can do things we do not want them to do. This is why side effects can exist. This is also why some pill shapes are differently shaped so they can change the way the pill is broken down. Some medications can only be absorbed in certain parts of your GI tract.

For example most doors need a key, you cannot use brick of iron you found in the ground, the iron needs to be shaped into the right shape in order to go into the right lock. So medications often fit into a key hole or a receptor that causes an action. If we put them through the skin, they may not be shaped correctly, or they may not even end up at the right house.

Some places we give medication may melt down that iron in a way we can’t use it in making a key at all. So we have to avoid those mechanisms that ruin the medication before it reaches its site of action. Skin also can have a variable makeup of medication, think of someone with literal thick skin. Birth Control implants release very small amount of medication, so a small implant can hang around for a long time releasing very small dosages of medication that are very strong pieces of iron. Levothyroxine acts on a very busy part of the body, the thyroid, which can have fluctuations in its function from day to day activities. So one consistent dose will not work all the time , and manufacturing a patch for a single person would be hard. In addition that medication given through the skin may be incapable of making it to the thyroid to fit in the right keyhole.

The last thing is that the medication may damage the skin itself depending on its makeup. our skin and body tissues have different makeups everywhere so it is like how some ovens are made of iron, or brick. I should not use a wooden oven in my house, it would burn down. But I can use a brick oven to shape the iron into the right shape without damaging my house.