Correct code and units for zofran 4mg

I have been having difficulty finding the correct code to use for Zofran 4mg tablets-- I was told S0181 was for 4mg, and Q0179 is for the 8mg tablet-- Has anyone been successful in getting reimbursed with either of these codes?-- I've had a commercial plan reject the S0181.
If I utilize the Q0179, I understand I will need to only bill one half (.50) of a unit, which is new for our practice. Looking for a code commercial plans will accept. Thank you for any input you can give!