Actually I wouldn't worry about trying to "split" them. If I were in that scenario and could really do with only that amount and make things that much more efficient I would just crush it up all together with a spoon/mortor-pestel and then try and see how I could split it up like that. If they are really tiny [I haven't seen those particular tabs before] and it would only require a TINY amount of it. I would just take a sugar free sucker or something, lick it, and then stick it to the pile of powder. That would give you a small dose, mask the [more than likely] horrible taste, and get it straight to your mouth without making a mess, so it can get nice and active.
Just a suggestion, but would be ideal for something tiny, instead of trying to split it into 18 pieces!