Is it safe to take 18 30 mg. pills of oxycodone a day?

It's Possible: If tolerance has developed, it's possible.Someone who is naive to opioids would stop breathing with this dose. This degree of tolerance would take awhile to develop or be caused by extreme pain like cancer metastasis.This is an unusually high number of pills, someone getting this number would probably be suspected to be diverting some of their meds until proven otherwise.

Be warned!: First of all, if you need that many pills to obtain relief, it sounds like you need some other forms of treatment to help you lower your pain. Are these oxycodone tabs mixed with Acetaminophen or plain? If they are a mixture, then you could be ingesting toxic levels of those products. Lastly, if you are taking this many now, what next? Where do you go from here? Options need to be reviewed.

No: You are most probably addicted to the drug. More people die now from prescriptional medications than from traffic accidents. Ask professional help.

If you are taking this massive dose, you are clearly addicted and should be detoxed ASAP. You need to find a knowledgeable pain specialist. Since you do not reveal reasons for all of this, hard to point out alternatives. If you have sleep apnea, you would be at high nocturnal risk. Get proactive NOW!