Which of the following concentrations of epinephrine are available in injectable lidocaine solution for dental anesthesia?

a. 1:5,000
b. 1:20,000
c. 1:25,000
d. 1:100,000

It is available in an injectable form as 2% without a vasoconstrictor, 2% with a vasoconstrictor [1:100,000 (0.017 mg) and 1:50,000 (0.034 mg) epinephrine].