My doctor warned me that I may suffer adverse side affects during the first week such as nausea,
headache,
constipation, dizziness, insomnia, hot flush, increased perspiration, vomiting, palpitations, and dry mouth. Luckily, I never felt nauseous, or had headaches, vomiting, palpitations, or any serious constipation. I take Temazepam on those nights I have difficulty sleeping. So far so good. Then again, I've never suffered severe pain 24/7.