Methods	Participants recruited from neurology departments; 13 international centres; out-patient based R, DB, three-period cross-over; 20 h washout One headache episode treated for each treatment
Participants	IHS diagnosis of cluster headache for at least three months; able to recognise an attack; excluded if taking any other medications to treat or prevent headache N = 153 randomised, 124 took ≥1 medication, 123 in efficacy analysis Mean age 44 ± 11 years 86% men Headache type: 73% episodic
Interventions	Zolmitriptan 5 mg, oral, n = 114 Zolmitriptan 10 mg, oral, n = 111 Placebo, n = 115 Patients instructed to take single dose of trial medication within 10 min of onset if headache was of at least 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: 5 (R2, DB2, W1)
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Yes	Computer-generated randomisation sequence
Allocation concealment?	Unclear	Not described
Blinding? All outcomes	Yes	Colour-matched placebo tablets. Four tablets taken in appropriate combination of zolmitriptan 2.5 mg and placebo