Can a one time dose of iv zofran cause serotonin syndrome? after 16 hours?

Can't say for sure.: People have developed serotonin syndrome with use of Zofran. Although we usually think of serotonin syndrome as occurring with very high doses of seritonergic medications (often taken over a period of time & with mulitple meds) - the bottom line is that some people can develop serotonin syndrome on a mildly seroternergic medication, at low dose with brief use.

IV Zofran would act within a few minutes, and effect would last several hours. Peak levels would occur early, and would not expect metabolic shifts in neurotransmitters to occur late. In other words, 16 hrs would be very unusual for the start of seratonin syndrome due to a one time dose.