On October 15, 2018, about 1416 eastern daylight time, an experimental amateur-built Hummel-Ultra Cruiser Plus, N245AP was substantially damaged when it was involved in an accident near Zephyrhills, Florida. The sport pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that he had been taking gabapentin four times a day for about 3 months before the accident, and since taking it, he noticed his reactions were not what they previously were. Earlier that day he took his first dosage of gabapentin then flew the airplane uneventfully several times in the airport traffic pattern at Zephyrhills Municipal Airport (ZPH), Zephyrhills, Florida. After securing the airplane, which included turning off the auxiliary fuel pump, he took a second dose of gabapentin then fueled the airplane bringing the total fuel capacity to about 8 gallons. After fueling, he received a call from his sister who asked him to fly over her location. He agreed but, "did not recall turning on the auxiliary fuel pump before departure." He departed ZPH, turned crosswind and announced leaving the airport pattern. He climbed to 2,000 ft mean sea level (msl) and turned southwest towards his sister's house. After about 5 minutes the engine “sputtered a few times” and then lost power completely. He checked the throttle and tried to restart adding that the engine turned over normally but did not start. He spotted a large clear field to his left and maneuvered for a forced landing. About 200 ft msl he maneuvered the airplane with no flaps deployed to avoid a tree that was ahead. At that time, "…the right wing [stalled] and the [airplane]" descended into the tree. A postaccident examination of the airplane by a Federal Aviation Administration airworthiness inspector revealed both fuel shutoff valves were on and both main fuel tanks were breached. The pilot also stated that following recovery of the airplane the header fuel tank was empty. The airplane's fuel system consisted of a 7.0-gallon capacity fuel tank in the leading edge of each wing near the wing root, a fuel shutoff valve for each tank, lines from each wing fuel tank to a 1-liter header tank, and then lines that supplied fuel to the engine. An electrically operated auxiliary fuel pump pulled fuel from the wing fuel tanks to the header tank located at the top of the fuselage behind the firewall. Based on the pilot's previous testing, the length of time that it took to deplete the fuel supply in the header tank by not having the auxiliary fuel pump on was about the same length of time of the accident flight. He also indicated there was no engine failure or malfunction. Gabapentin, often marketed with the name Neurontin, carries the following warning regarding central nervous system symptoms, “Patients should be advised that gabapentin may cause dizziness, somnolence and other symptoms and signs of central nervous system depression. Accordingly, they should be advised neither to drive a car nor to operate other complex machinery until they have gained sufficient experience on gabapentin to gauge whether or not it affects their mental and/or motor performance adversely.”