Tension headache

All other primary forms of headache

Cardiovascular, Central Nervous system (CNS) and autoimmune diseases

Gastrointestinal disease

Previous or clinical signs of mental illness or substance abuse.

Participation in a clinical study of a medicinal product without regulatory approval or marketing authorisation within 1 month prior to this trial

Pregnancy/nursing

Daily intake of medication (except oral contraceptives)

EP4-receptor Antagonism and Prostaglandin E2 (PGE2) in a Human Headache Model