Two of the most effective disease-modifying treatments (DMTs) are Tysabri and Fingolimod.
The licensed medicines can reduce the frequency and severity of MS attacks, and in some cases can slow the progression of disability.
Just 31% of people eligible for Tysabri are currently receiving it in Northern Ireland.
Based on NICE (National Institute for Health and Care Excellence) estimates, 16% of people with relapsing remitting MS in the region may be eligible for Fingolimod, the report by the MS Society also revealed.
It is an oral tablet which can reduce relapses by up to 60%.
In Northern Ireland, around one in every 500 people live with the disabling neurological condition.
The region has one of the highest rates of multiple sclerosis in the world.
Tom Mallon, Head of the MS Society in Northern Ireland, said: "These findings worryingly suggest that the likelihood of someone receiving a life changing treatment is often based on luck - like where they live or how helpful their healthcare professional is - rather than their genuine clinical need."
He continued: "In Northern Ireland eligible people with MS are unable access to the most up-to-date and effective treatments.
"These are treatments which are proven to reduce relapse rates and which can greatly improve quality of life by removing the need for people with MS to administer their medicines via injection".
"People with MS are facing a lottery when it comes to accessing the care and support they need to manage their condition and this must change."
The MS Society launched its 'Stop the MS Lottery' campaign on Monday to mark the first day of MS Week, which continues through until Sunday.
They are calling for all people with the condition to have fair access to the treatments and services they need, when they need them, wherever they live in the UK.
The charity said that their report 'A lottery of treatment and care: MS services across Northern Ireland and the UK' uncovers major disparities across the UK in access to MS medicines, social care support, employment support and health professionals.
More than 10,000 adults with MS in the UK responded to a survey, which was used to inform the report.
They were asked what services they needed and to what extent these needs had been met over the previous 12 months.
Meanwhile, Northern Ireland is leading the way in access to MS specialists, such as neurologists and MS nurses.
Over 90% of patients were able to see a neurologist when they needed to, compared to just 72% in Wales.
However, access to care in the community is much worse in Northern Ireland than in the rest of the UK.
Only 6% of people with MS in the region, who saw a nurse had them come to their home, compared to 24% across the UK.