Has anyone experienced massive headaches and vomiting with Methadone?

After a year of Vicodin for pain relief, my neurologist wanted me to try methadone. I took 5mg in the am for 1 week, then 5mg am and pm. I get in home IVIG infusions every other week for two days and on the second day I woke up to an extreme headache then vomited. I went back to the vicodin for a week and the symptoms disappeared. Now my neurologist wants me to try the methodone again, but cut the tabs in half. I am afraid of getting sick again, has anyone else been prescribed methodone?( I am also taking Gabopentin) I would appreciate any feedback. Peace Nancy