I don't think it should make you go into withdrawal, but the naltrexone might block or partly block the buprenorphine (Suboxone). As I understand it, naltrexone only causes withdrawal when taken after opioids. If you take naltrexone before an opioid it generally blocks the opioid. Naltrexone's effects lasts for a long time, much longer than it's half-life in your system, so the naltrexone will still be on your receptors after 12 hrs. The half-time of opioid blockade by naltrexone ranges from 72 to 108 hrs. I was going to suggest you not bother taking the Suboxone, but buprenorphine has a very high binding affinity for opioid receptors and it may be higher than naltrexone's binding affinity, which means it might kick the naltrexone off the receptors and replace it with itself. So you might still be able to feel some effects from buprenorphine. I'm not sure how much though. Please be careful, even though it's hard to have a fatal overdose from bupe alone it's not impossible and if you are on naltrexone you might have a low tolerance.
Rx = prescribe or prescription
(XR = extended release)