[STUDY] The effect of glatiramer acetate treatment on pre-existing headaches in patients with MS: During the first 6 months of glatiramer acetate therapy in 82 consecutive patients with multiple sclerosis, in only 6% frequency of pre-existing headaches increased by more than 50%. This is less than the headache aggravation reported in an earlier study in up to 35% of patients during the first 6 months on interferon beta.