I know it's been a few hours so your situation has likely changed but I'm going to go ahead & assume you are in precipitated withdrawal! I sympathize it's horrific! Whether or not it's particularily dangerous depends on your health conditions.
If you're a healthy individual who can normally tolerate full blown withdrawal without medical issues arising you should be ok. What is occurring is equivalent to (& actually is) full blown opioid withdrawal.
If you consume buprenorphine (the active ingredient in Subutux) while you still have a full a full agonist (Methadone in this case) in your system you will go into withdrawals. To put it simply the Subutux likely caused you to go into preicipitated withdrawal.
There is very little that can be done once this occurs. I myself have a lot of experience with both substances but have always made sure to switch to a short acting opioid before switching to buprenorphine. Very few times have I dosed buprenorphine to soon. I learned quickly when I did.
I was able to break back through the PW (Precipitated Withdrawal) as I was precipitated off a short acting full agonist & was able to break back through with various IV opioids. (Note this can be dangerous & should not be attempted without proper knowledge.)
Either way you will likely either be forced into one of two options. To "ride it out" or try to "break through" & get back to normal. Sadly enough I need more information to help you decide a course of action.
Without knowing your usage & medical history, the dosages involved & the exact time frames I can't offer much advice. If you're still dealing with the issue & want more advice please post an update with more information. I'll try to keep an eye on this thread so I can give you feedback ASAP.
In the meantime you have my best wishes & I hope that you make it through this experience as best as possible!