system
Given the following post, respond as if you're commenting on Reddit:
human
To what extent can medicine applied to the skin affect joints?

I see TV ads for such products.  Usually it's for back pain, but one currently running in the UK has a graphic with arrows - presumably the path of the active ingredient - penetrating the skin and going to work on a knee joint. Is there such a transport mechanism in the body?  How does it deliver an effective dose without contaminating blood and organs?
gpt
NSAIDs (Non steroidal anti-inflammatory Drugs) can be absorbed through the skin. They are best used on joints on the body that are close to the surface of the skin.


They can be absorbed into the blood stream, however, this isn't common. The toxicities can lead to stomach ulcers and high blood pressure.

Edit: Missed a question - they often also have dosage recommendations or sizes of amounts to use in the instructions.