No. Whatever you took in 2018 in excess of your RMD is just an extra distribution in 2018, not an RMD.
However, the amount distributed in 2018 in excess of your 2018 RMD is eligible for rollover (provided that it would not result in a violation of the one-rollover-per-12-months rule). If it has been less than 60 days from the date of the December 2018 distribution, you can roll the money over back into the IRA.
If you have not yet reached the 60-day rollover deadline but you have done a rollover within a year of the date of the December distribution, you could instead deposit the amount in excess of your 2018 RMD into a Roth IRA as a Roth conversion. You would still owe the tax on the amount converted to Roth, but it would then be in an account that will grow tax free once you have met the 5-year holding period for qualified distributions from your Roth IRAs.
