Kostas Kenteris and Katerina Thanou have denied charges they knowingly avoided dope tests.
The Greek pair were charged by the International Association of Athletics Federations (IAAF) after missing tests in Tel Aviv, Chicago and Greece.
But in letters to the IAAF they rejected the claims, which are now being investigated.
An IAAF statement said it "will reach a decision as to whether the explanations are acceptable in the next few days".
If the pair's explanations are rejected they "will be provisionally suspended pending a hearing before a disciplinary tribunal in Greece".
Their former coach Christos Tzekos has also been charged with distributing banned substances. He has been given until 21 December to respond.
Under IAAF rules, Kenteris and Thanou could receive a maximum one-year suspension.
The athletes already face a criminal trial after being charged with avoiding a drug test on the eve of the Athens Olympics and then faking a motorcyle crash.
Tzekos also faces charges of distributing prohibited substances
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No date for the trial has yet been set and again Tzekos is also facing charges.
The IAAF issued an official warning to the trio last year after they were discovered training in Qatar rather than in Crete, where they had said they would be.
All athletes must inform their national federations where they are at all times, so they can be available for out-of-competition drugs tests.
But Kenteris and Thanou then went on to skip tests in Tel Aviv and Chicago, when they decided to fly back to Greece early.
Then just before the Olympics, the pair dramatically missed another test in Athens and withdrew from the Games.