Two cocaine users in Glasgow have become the first in the UK to be treated for a rare and life-threatening condition, linked with taking the drug.
Methaemoglobinaemia can cause loss of consciousness, seizures, coma and possible death.
NHS Greater Glasgow and Clyde said the development of the condition could be linked to the consumption of unusually large amounts of cocaine.
It may also be due to the presence of an unknown agent in the drug.
Both cases happened within a five-week period and the two patients have now recovered and been discharged.
They were said to be "very lucky" to survive.
Apart from the fact that the cases are so rare, what is also of concern is that both cases occurred over a short five-week period and both were in the Glasgow area
Dr Eleanor Anderson
NHS Greater Glasgow and Clyde
Dr Eleanor Anderson, NHS Greater Glasgow and Clyde's consultant in public health, warned health professionals in the area to be on the look-out for the condition.
"We are uncertain as to the causes of Methaemoglobinaemia in these two cases and our investigations are ongoing but it may be related to the consumption of an unusually large quantity of cocaine, or the presence of an unknown agent in the cocaine," she said.
"Apart from the fact that the cases are so rare, what is also of concern is that both cases occurred over a short five-week period and both were in the Glasgow area.
"Both patients have now recovered and been discharged but they were very lucky - so serious is this condition that they may well have not survived."
Methaemoglobinaemia occurs when an increased quantity of the iron of haemogloblin is oxidised to the ferric form, creating an abnormality with a lack of oxygen in the blood.
Symptoms include blue lips, headache, abnormal heart rate, breathlessness, fatigue, exercise intolerance, dizziness, loss of consciousness, seizures and in severe cases coma and death.
Dr Anderson advised any cocaine users with these symptoms to seek urgent medical attention.
Source - http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/7876387.stm