The purpose of this study is to evaluate the bioequivalence between Orfadin 20 mg and 10 mg capsules in healthy volunteers.

This is an open, randomized 2-way crossover study in 12 healthy volunteers. Subjects will receive single oral 20 mg doses of nitisinone administrated as one 20 mg capsule or as two 10 mg capsules of Orfadin. There will be a 3-week washout period between the doses.

There will be a screening visit within 3 weeks prior to the first dose. During each treatment period, subjects will be admitted to the clinic from the afternoon on the day before drug administration (i.e., on Day -1) and remain at the clinic until the 48-hour post-dose blood sample has been collected in the morning of Day 3. They will then return for ambulatory visit in the morning of Day 4 (72-hour sample). A follow-up visit will take place 7-14 days after the last dose.

Inclusion Criteria:

• Healthy male and female volunteers between 18-55 years of age, inclusive.
• BMI between 18,5-30,0 kg/m2, inclusive.

Exclusion Criteria:

• Subjects with current keratopathy, or other abnormalities found by slit-lamp examination.
• Subjects who are heavy smokers or consume more than 5 cups of coffee per day.
• Subjects with history of drug and/or alcohol abuse or a positive drug screen or alcohol breath test.
• Subjects with positive screens for hepatitis B surface antigen, hepatitis C antibodies and human immunodeficiency virus (HIV) 1-2 antibodies.
• Subjects who were enrolled in another concurrent clinical study or intake of an investigational medicinal product within three months prior to inclusion in this study.
• Subjects who donate more than 50 mL of blood within 60 days prior to drug administration or donate more than 1,5 liters of blood in the 10 months prior to first drug administration.
• Female subjects that are pregnant or breastfeeding.
• Female subjects of childbearing potential and all male subjects must be willing to use effective forms of contraception.