Methods	Participants recruited from five international study centres; out-patient based R, DB, three-period cross-over; 24 h washout One headache episode treated for each treatment
Participants	Established IHS diagnosis of cluster headache N = 92 randomised, 69 took ≥ 1 medication Mean age 40 ±10 years 87% men Headache type: 64% episodic
Interventions	Zolmitriptan 5 mg, nasal spray, n = 65 Zolmitriptan 10 mg, nasal spray, n = 63 Placebo, n = 61 Patients instructed to take medication when headache reached moderate intensity Escape medication permitted after 30 min
Outcomes	Primary: Pain relief to mild or none at 30 min on a five-point scale Secondary: Pain-free at 30 min; relief of associated symptoms; adverse events/withdrawals; use of rescue medication
Notes	Results for primary outcome reported for episodic and chronic subgroups Oxford Quality Score: 4 (R1, DB2, W1)
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	Not described
Allocation concealment?	Yes	Randomization schedule provided by sponsor and kept by pharmacies until study completed
Blinding? All outcomes	Yes	Matching placebo