Zawadka, whose sample tested positive for anabolic steroid clenbuterol and stimulant methylhexaneamine during the New South Wales Short Course Championships, was banned by Swimming Australia which oversaw the tests.
"Zawadka waived his right to a hearing and as a result, accepted the mandatory four year sanction," the ASADA said, adding that the suspension will be backdated to Nov. 11, 2015.
"This means he is ineligible to participate, as an athlete or support person, in any sports that have adopted a World Anti-Doping Agency compliant anti-doping policy until 12 November 2019."
Zawadka was the Australian champion in the 50 metres short course breaststroke when he represented KRB Aquatics in the 2014 Australian Short Course Championships in Adelaide.
(Writing by Sudipto Ganguly in Mumbai; editing by Amlan Chakraborty)
