Hi, I am an American Board Certified Neurologist with vast experience in diagnosing & treating all types of neurological & other medical conditions including the concerns of “Possible drug interactions” you have mentioned here and I am very glad to help you with your health concerns.
Xanax is not an example of MAOI
Xanax can be taken together with Sudafed
There are no major or serious drug interactions expected to occur if these two used together
Xanax due to its sedative properties in fact counters the insomnia created by the Sudafed, so Xanax can be used in your case to counter the sleeplessness caused by Sudafed
You have mentioned dose of Xanax 5 mg, I am not sure if you meant 0.5 mg, because it is commonly used around 0.5 to 1 mg per each dose. A 5 mg per dose (single dose) is considered as a high dose.
Once again to your main question, Xanax is not an example of MAOI, and also Xanax is not expected to cause any major or serious drug interactions if used together with Sudafed, so you can use them together, and it can counter the insomnia caused by Sudafed, and please make sure you use the correct dose of Xanax as mentioned above.
Please let me know if you have any further questions, and please click a positive rating (preferably 5 Star/Excellent) to credit for the time & effort put by me in answering your health question, and this is the only way I will be credited for my service to you. If you have follow-up or additional questions you can ask them after the rating too.