Medics were put on alert today after two Scottish cocaine users suffered a life-threatening condition associated with the use of the drug.

Two cocaine users in the Glasgow area needed treatment for Methaemoglobinaemia, which can cause seizures, coma and death.

The condition is so rare that these are the only known UK cases linked with cocaine use.

It is not known what causes it, but it may be linked to the consumption of an unusually large quantity of cocaine, or 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.

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.

She said: "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.

"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 of Methaemoglobinaemia 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 who suffer such symptoms to seek urgent medical attention.