South Africa international duo Bjorn Basson and Chiliboy Ralepelle will face a judicial committee in Cape Town today.
The Springbok players tested positive for the banned stimulant methylhexaneamine following their 23-2 win over Ireland in the first Test of their autumn Grand Slam tour. They were sent home and their 'B' samples also tested positive.
But it is thought that a supplement used by the players may have been contaminated without their knowledge.
The banned substance was downgraded from a non-specified substance to a specified substance on January 1, this year, six weeks after the duo were tested positive.
The change of specification means if there is a logical explanation for testing positive, you can be cleared instead of receiving a two-year automatic ban which was previously the case.
There is a hope that in the worst-case scenario, the duo will be banned for three months, which will be set retroactively so that they have already served their sentences.
That would allow the duo to start the Bulls' Super Rugby campaign that kicks off in February.
"They are key guys and we obviously are holding thumbs that things work out well for us at the Bulls," said Bulls head coach Frans Ludeke.
"There is something that we all can learn out of this whole situation and a lot of positives can come out of it. For us and for the season ahead, we obviously hope there will be some good news.
"If we get good news with those two, we will regroup with both of them and bring them back into the system as quickly as possible. We will work out a strategy to get them back into action as quickly as possible.
"They have been out of the system for the last three months, but have been training on their own, away from the team. We will have to make sure we close those gaps."