A Pharmacokinetic Substudy of the TDE-PH-304 Protocol

A Pharmacokinetic Substudy of Subjects Transitioning From Twice Daily to Three Times Daily Dosing of UT-15C SR (Treprostinil Diethanolamine) in the TDE-PH-304 Protocol

A sub-study to the TDE-PH-304 protocol to assess the pharmacokinetics of patients transitioning from a twice daily dosing regimen of oral treprostinil to a three times daily dosing regimen.

As noted above in "Brief Summary".

Inclusion Criteria:

1) Only subjects who are eligible for and have entered into Protocol TDE-PH-304 may participate in this substudy.

Exclusion Criteria:

1. The subject must voluntarily give informed consent to participate in the substudy.
2. No dose changes to study drug are made within 5 days of the pharmacokinetic (PK)substudy visits.
3. No additions or deletions to concurrent medications are made within 7 days of the pharmacokinetic substudy visit. Note: changes to diuretics and/or anticoagulants are permitted.
4. The preceding evening dose of study drug should have been taken 9 to 13 hours prior to the BID dose and 6-10 hours prior to the TID morning dose of study drug to ensure a trough level of study drug for PK sampling.
5. Subject dosing of study drug on the day of PK sampling must be observed in the clinic by study personnel.
6. Subject has not experienced a significant loss of blood (> 450 mL) within the last 6 weeks of the pharmacokinetic substudy visit.
7. The subject must not be receiving any CYP 2C8 inducers or inhibitors