I placebo- kontrollerede forsøg af PAH med den anbefalede dosis var den mest almindelige bivirkning, som blev vurderet til muligvis at være relateret til Thelin, hovedpine hos 15% af patienterne, og perifert ødem og nasal kongestion, hver hos 9% af patienterne.
At the recommended dose during placebo-controlled trials in pulmonary arterial hypertension PAH, the most common adverse drug reactions considered to be at least possibly related to Thelin treatment were headache in 15% of patients, and peripheral oedema and nasal congestion, each in 9% of patients.