The Researchers overall goal is to evaluate the benefit and utility of preemptive genotypic data to guide post-operative nausea and vomiting treatment in the bariatric surgical population. The hypothesis is that using genotypic variation in CYP2D6 to select the appropriate 5HT3 serotonin receptor antagonist to treat PONV will decrease rates of PONV in the bariatric surgical population.

Inclusion Criteria

• A Mayo Clinic patient scheduled to undergo any bariatric surgical procedure, including Roux-en-Y gastric bypass, sleeve gastrectomy, or duodenal switch.
• Patient age 18 or above.
• Patients must understand and provide written informed consent and HIPAA authorization prior to initiation of any study-specific procedures.
• Patient is willing to engage in a medication adjustment as part of their clinical visit (when needed).

Exclusion Criteria

• Patient with uncontrolled concurrent illness including psychiatric illness, or situations that would limit compliance with the study requirements or the ability to willingly give written informed consent.
• Patients that deny access to their medical records for research purposes will not be included in this study. Also any patient who will be unable to have genetic testing at minimum of 1 week prior to scheduled surgery or with allergies to ondansetron or granisetron.
• Any patient with prior genetic testing that is readily available in the medical record will be excluded from this study.
• Any patient that is pregnant

Adverse Events were collect from baseline (surgery) to one week post surgery, for approximately one week.