The cyclists were banned from the sport for two years after testing positive for EPO (erythropoietin), which boosts red blood cells to enhance performances, Xinhua reported Wednesday citing daily O Estado de Sao Paulo.
According to the Brazilian Cycling Confederation (CBC), both athletes declined to appear for a second test. The first test was conducted in June.
Marcia, 23, comes from a family of cyclists, and in addition to being part of the national cycling team is also a member of Spain's professional cycling squad, Bizkaia-Durango, which competes in elite events, including the Women's Road World Cup organised by the International Cycling Union.
Due to the ban, Marcia will not be able to participate in the 2016 Olympic Games to be held here.
Nayara is the Brazilian champion in the Under-23 category.
The suspension automatically annuls both their records following the date of doping. The CBC's decision to suspend the athletes was taken Oct 15, though it was not made public until earlier this week.
The first Brazilian cyclist accused of doping in 2014 was Marcio Augusto Gripp, suspended in January for testing positive for anabolic steroids and other banned substances. In total, five cyclists have been suspended this year.