Title: Impact of collaboration between primary care pharmacists and a neurologist in the management of headache patients - A retrospective chart review Objectives: To characterize patients referred to the University of British Columbia's Pharmacists Clinic by a neurologist for headache management and evaluate clinical outcomes related to headache burden. Methods: A retrospective review of all patients referred to a clinic pharmacist by a neurologist between 2014 and 2017 was conducted. Pertinent data to headache management (patient characteristics, headache type, frequency and severity of attacks, use of medications) were extracted from patient's electronic medical records for initial and follow-up pharmacist visits. Results: A total of 115 patient charts were reviewed (74.8% female, mean age 48.5 years). On initial pharmacist visit, 29.6% of patients had a diagnosis of chronic migraine; 29.6% has episodic or mixed migraines with the remainder having non-migraine headaches or being undiagnosed. Initial headache severity was reported as mild, moderate or severe in 10.4, 42.6 and 33% of patients, respectively with data unavailable for 14% of patients. Headache severity was not consistently reported on follow-up. Mean initial headache frequency was 19.1 attacks per month, decreasing to 7.9 on follow-up. Mean initial headache duration was 24.6 hours, decreasing to 7.2 hours on follow-up. Pharmacists recommended: non-pharmacological measures, abortive therapy alone, pharmacologic prophylaxis alone and a combination of abortive and prophylaxis therapies for 79.1, 5.2, 41.8 and 40% of patients, respectively. Medication overuse headache was suspected in 42.6% of patients with educational interventions provided. De-prescribing of drugs was recommended for 51.3 % of patients. Conclusion: Pharmacist interventions, in collaboration with a neurologist, demonstrated clinically significant reductions in frequency and duration of headaches. Pharmacists have the unique knowledge, skills and accessibility to make meaningful impacts for headache sufferers.