Kent sends a link to an article about a surgical team in Vancouver:
A team of Canadian surgeons got a shock when the patient they were operating on began shedding dark greenish-black blood, the Lancet reports.
The patient had been taking large doses of sumatriptan – 200 milligrams a day.
This had caused a rare condition called sulfhaemoglobinaemia, where sulphur is incorporated into the oxygen-carrying compound haemoglobin in red blood cells.
Go Spock.