Study to assess the safety of terbogrel during open-label, long-term treatment in medically stable or improving patients with primary pulmonary hypertension who have completed the 12-week, double-blind randomized trial of terbogrel (protocol 528.19)

Inclusion Criteria:

Patients who

• completed the preceding primary pulmonary hypertension, double-blinded clinical trial of terbogrel (protocol 528.19)
• provide informed consent to participate in this trial
• are in a stable or improving medical condition, in the opinion of the investigator
• enter the study immediately upon their completion of the preceding double-blind Trial 528.19, or enter the study within one month of completing the preceding trial as long as their medical condition has remained stable or continues to improve in the interim

Exclusion Criteria:

• Development of an unstable medical condition during or following completion of the preceding clinical trial which, in the investigator's opinion, may be worsened by treatment with terbogrel
• Premature discontinuation of the preceding terbogrel clinical trial due to an adverse event or for any other reason
• Pregnant or nursing women, or women of childbearing potential (less than one year postmenopausal or not surgically sterilized) who are not using adequate methods of birth control