Thew oxycontin has nothing whatsoever to do with the acne. That being said, get an hva1c. Diabetes can cause acne.
I have not heard of narcotic drugs having this effect of clearing skin.
If your skin is oily, white vinegar is effective as an astringent. Or try a tea tree oil soap. Eat a healthy diet, high in vegetables, fruits, and lean, preferably organic meats, poultry and fish.
Find out if you have food allergies and avoid problem foods.