John’s Wort, INR: International Normalised Ratio, CYP: Cytochrome P-450 enzymes, P-gp: P-glycoprotein, BP: Blood Pressure, HR: Heart Rate, PAD: Peripheral Artery Disease, CCB: Calcium Channel Blockers, HA: Headache, N: nausea, V: vomiting, ADHD: attention-deficit hyperactivity disorder, OCD: obsessive-compulsive disorder, GI: Gastrointestinal, ICB: intracerebral bleeding, BF: Breast Feeding, OC: Oral Contraceptives. This evidence concerns the gene PGP and Headache.