Phenylbutazone is a non-steroidal anti-inflammatory drug (or NSAID), with strong analgesic and anti-inflammatory properties.
Chemically speaking, phenylbutazone is a pyrazolone derivative.
Phenylbutazone - Chemical Structure
Due to the side effects it can cause, phenylbutazone is currently only used externally for topical use. In fact, it is available in the form of a cream.