Depends upon the dose, if it's 4 mg of buprenorphine one single time, by 30 hours you'll have roughly 75 percent of your mu-opioid receptors free, and you may be able to feel an appropriately compensated dose of codeine at 30 hours. If it's 8 mg of buprenorphine one time or more, I'm not sure how effective codeine would be at 30 hours, if at all.