OBJECTIVES: Drug therapy in Multiple Sclerosis (MS) accounts for a significant proportion of the economic burden of this disease.  Expenditure on disease-modifying-therapies (DMT) in Ireland was €32.7 million in 2009, 1.63% of total pharmaceutical expenditure.  In addition to DMT, other non-DMT drugs are used to treat MS symptoms.  This study describes the patterns and cost of non-DMT (other) drug utilisation in Ireland.  METHODS: A cohort of patients dispensed a DMT during 2009 were identified from a national prescribing database.  An analysis of all other drugs dispensed for this cohort during 2009 was undertaken.  RESULTS: A cohort of 2749 people on DMT was identified (39.3% of the estimated Irish MS population) 69.0% of whom also received other drugs costing €2.7 million (estimated 7.6% of total MS drug costs).  The mean other drug cost per person on DMT was €1417 (SD €1863).  Drug classes contributing most to other drug costs were antiepileptics (17.1%) used for neuropathic pain, urinary antispasmodics (8.1%) and muscle relaxants (7.0%).  The top 10 drugs by cost included pregabalin, gabapentin, modafinil, tizandine, tolterodine, evening primrose oil, atorvastatin, venlafaxine, baclofen and escitalopram (39.9% of other drug costs). The most commonly prescribed drug classes – antidepressants, analgesics and NSAIDs, dispensed to over 20% of the cohort in each case, accounted for just 12.7% of other drug costs.  CONCLUSIONS: Characterisation of non-DMT drug use provides useful information for clinicians, healthcare payers, and those undertaking cost-of-illness studies.  While these drugs account for a smaller proportion of overall costs than DMT, they are an indication of overall morbidity and wider resource utilisation e.g. urological drugs as an indicator for physiotherapy and incontinence equipment.  These results can be considered in the design of future cost-of-illness surveys which often include an exhaustive list of individual drugs.