Is it safe to take methadone after taking suboxone?

My fiancee was on Methadone approximately 60-70mg per day. He was prescribed 8mgs of suboxone 2x/day & specifically advised to wait at least 72 hours after his last metahdone dose to begin the treatment. After 17 hours of no meth he felt he needed something so he took 8mg of suboxone.
No one has to tell me this was a huge mistake. I told him not to and he wouldn't listen. After looking online for the last 3 hours I have some understanding as to why it was not ok to take them because of the bad wd affect it can have with so much meth in his system.
Within 30 minutes he was experiencing what he calls the worst wd symptoms he's ever had. He had the runs, throwing up, cold sweats, muscle spasms/pain, the shakes, rls. He called the doc who told him to take 2 more (16mgs) about 2 and a half hours after his 1st dose. He desperately wants to take the methadone to ease his symptoms.
Can he take methadone now after taking the suboxone? How long should he wait?

: http://alcoholdrugstreatment.info/is-it-safe-to-take-methadone-after-taking-suboxone