Ibuprofen (trademarked at Advil or Motrin) is so popular amongst hikers and climbers that it is often called Vitamin I.
Ibuprofen is an over the counter pain reliever and anti-inflammatory that can speed recovery during training or the main event. Muscle pain caused by inflammation can occur as a result of overuse, extended exercise, or physically-demanding work. In these situations, the pain tends to involve specific muscles and begins shortly after the activity.
I carry Ibuprofen in my first aid kit on backpacking trips to manage knee pain. If I've been doing a lot of elevation and my knees hurt, I'll take 400 mg (2 tablets) with food, before bed, and the pain will be gone the next day. I also use it periodically at home for the occasional headache or if I've strained something in the gym. It's an excellent anti-inflammatory when taken properly for short term therapy and can greatly speed recovery.
So, I'm always surprised when I meet hikers on the trail who are clearly experiencing muscle pain and don't take anything for it. They don't know what Ibuprofen is and prefer to limp along in agony rather than treat the problem before it gets worse.
I can understand not wanting to take drugs unnecessarily in this day and age, but I've often suspected that peoples' reluctance to take Ibuprofen on the trail, at least in the US, stems from some deeply seated Puritanical meme in American popular culture. Is there any truth to that?