Study To Determine The Pharmacokinetics Of Sulfasalazine In Children With Juvenile Idiopathic Arthritis

Inclusion Criteria:

- Patients with a diagnosis of oligoarticular, polyarticular, psoriatic or
enthesitis-related JIA as determined by ILAR criteria. Patients who have been
continuously treated with generic sulfasalazine delayed release formulation and have
tolerated the product for at least 3 months prior to study enrolment and who are
switched to Azulfidine-EN at least 8 days prior to Day 0 are eligible.

- Patients must be at least 6 years of age and has not reached his/her 18th birthday
prior to the Baseline Visit (Day 0).

- Onset of JIA must have occurred prior to the patient's 16th birthday.

- Patients must weigh at least 20 kg.

- Patients must be on sulfasalazine 500 mg delayed release tablets and the total daily
dose must be within the specified range of 30-60 mg/kg/day with a maximum daily dose
of 3 g/day

Exclusion Criteria:

- Patient currently with systemic features of systemic JIA.

- Hypersensitivity to sulfasalazine , its metabolites, sulfonamides or salicylates.

- History of sensitivity to heparin or heparin-induced thrombocytopenia.

- Inability to swallow whole (uncrushed) sulfasalazine 500 mg delayed release tablets
as required by protocol