Identify this pill Small round white with R 35 imprinted?

The pill you're referring to is a 2mg dose of Clonazepam (generic version of Klonopin), which is a Benzodiazepine family drug. It is in the same family as Diazepam, which is more commonly known as Valium.

Clonazepam is generally prescribed for seizures/panic attacks, but such drugs are also used in experimental form for pain control. It is up to the patient to determine if it is effective or not on pain, though it will most likely make you drowsy.