What bad effects do pain meds have on the brain?

Drowsiness and other: Opioid pain medication addiction is a huge problem in today's society. Long term use does frequently lead to dependence and addiction.Our brains develop a tolerance for the drug and we have to take larger doses to control the pain or to ward off withdrawal symptoms. Usual side effects are drowsiness, tiredness, sweating, constipation, slurred speech, poor coordination and attention.