Only 12 patients in the Republic have been treated with Tysabri, the multiple sclerosis (MS) medication withdrawn from the market this week by the pharmaceutical company, Elan.
None of the 12 was given the drug in combination with another agent, Avonex. It was this combination therapy that gave rise to two people in the US developing a rare and potentially fatal neurological side-effect.
A neurologist who supervised the Tysabri trial here told The Irish Times last night that all patients had now been taken off the drug. "Neurologists are in the process of contacting patients while we await further information from the company (Elan)," he said. The specialist predicted that Tysabri would be licensed as a single-drug treatment "in time".
"We must wait for further research. It would be rash to say that this drug will never be available to patients with MS."
He confirmed that none of the 12 people given the drug had developed progressive multifocal leukoencephalopathy (PML), the side-effect detected in patients who were given a combination of Avonex and Tysabri.
PML is a progressive and uniformly fatal disease of the central nervous system.
It usually affects patients whose immune systems are already compromised by disease. PML is caused by the activation of the JC virus, which 80 per cent of people carry in a latent form.
A spokeswoman for a helpline run by the MS Society, a patient advocacy group, said it received a least three times the usual volume of calls yesterday, most of which were triggered by the drug scare.
"Tysabri represented a great hope for people with multiple sclerosis. We haven't given up on the drug. Using Tysabri on its own remains a possibility," she said in reference to earlier research that found a 66 per cent reduction in the number of relapses experienced by MS patients when treated with Tysabri alone.
Some of the callers to the help line were looking for reassurance that interferon therapy, such as Avonex, remained safe to use.
MS attacks the brain and spinal cord by destroying the sheaths that cover nerve fibres and by damaging the nerve fibres.
The resultant scarring interferes with the smooth transmission of impulses travelling along the nerve to and from the brain.
The symptoms of MS are highly variable and individualised but include mood symptoms, tremor and a difficulty maintaining balance. Double vision and numbness are also common.
Most people with the disease have periods of relatively good health alternating with debilitating flare-ups.
According to the MS Society, the disease affects between 5,000 and 6,000 people in the Republic. The telephone number of the MS Society helpline is 1850 233 233.