Hi Christi,
OxyContin is oxycodone HCl, a compound which comes in immediate and controlled-release formulations, indeed is a Schedule II narcotic. While quite effective at controlling moderate to severe pain, taken over a sufficient period it will, like all opioid analgesics (compounds chemically related to morphine), result in tolerance and dependence. Sadly, it has been subject to much abuse and the manufacturer has gone so far as to stop shipping the highest dose tablets (160mg) and to post various warnings, as have governmental agencies like the FDA and DEA.
This medication certainly can have side effects of concern to divers, including nausea, vomiting, sleepiness, dizziness, headache, weakness, anxiety, euphoria and confusion. Not only could any of these adversely safe scuba, but some could be mistaken for the signs/symptoms of DCI and vice-versa.
While not all side effects are likely to appear in every user, and often moderate with continuing time on the drug and alterations in dosing, there is no guarantee that they will dissipate altogether.
Drugs of this class are especially worrisome when used in combination with other products that effect the CNS such as alcohol, antidepressants, antihistamines, other pain relievers, tranquilizers, seizure medicines and muscle relaxants. Dangerous dizziness or drowsiness well could result by combining OxyContin with these types of drugs, as could respiratory depression, possibly fatal.
The OxyContin controlled-release formulation is intended to provide relief over a 12 hour span, although traces can be detected in the urine for 1-3 days after the last dose.
The effects of depth on OxyContin's activity per se is unknown, but it would not be unreasonable to suspect that the effects of nitrogen narcosis on mentation and behavior could be additive with those of the drug.
Noted diving medicine authority Ern Campbell, MD lists among obvious reasons why a person should not be allowed to dive disorders/medications that may lead to altered consciousness or to erratic and irresponsible behavior.
Given the above, the diver on OxyContin will want to be medically cleared to dive.
Regards,
DocVikingo