This is a pilot study to evaluate pain responses from two different approved medications
(ketamine and fentanyl) in the treatment of pain after rattlesnake envenomation (RSE). Both
medications are currently used in standard practice to treat both acute and chronic pain and
are options for pain management after RSE. Multiple studies exist showing ketamine to be both
safe and effective for the treatment of acute pain, and to be as good as or better than
opioids for this indication. The specific comparison of ketamine to fentanyl, however, has
never been studied for the treatment of acute pain after rattlesnake envenomation in the
United States. The investigators plan to measure pain scores after a single dose of ketamine
or fentanyl in patients shortly after being envenomated, followed by continued treatment of
pain guided by the treating doctor. There will be no restrictions on additional pain
medications given and no other changes to the treatment of these patients during their
hospitalization. This research is important because pain after RSE can be difficult to
control and may require frequent, high doses of opioids for several days. An effective
non-opioid medication would be helpful both to better-control pain and to reduce exposure to
opioids in this patient population. This study will compare patient-reported pain scores
after receiving a single dose of ketamine or fentanyl in patients with rattlesnake bites who
have been admitted to the toxicology service at Banner - University Medical Center Phoenix
(BUMCP).