The main event for the card will be former UFC heavyweight champion Tim Sylvia facing off with Jason Riley. FiveOuncesOfPain.com had previously reported the bout after Riley had leaked the news on his MySpace account.
Adrenaline IV will take place at the Mid-America Center in Council Bluffs, Iowa on September 18.
Alexander will be looking to get back on track after suffering three consecutive defeats in the UFC to the likes of Thiago Silva, James Irvin and Eric Schafer. The Omaha, Nebraska established himself as a powerful knockout artist prior to his recent losing skid, stopping both Keith Jardine and Alessio Sakara in impressive fashion.
Pendergarst is an experienced veteran with an overall record of 11-14 that has previously been stopped by Shane Carwin and Antoni Hardonk. He is currently riding a five fight losing streak.