May 26 (HealthDay News) -- United Therapeutics has received approval from the U.S. Food and Drug Administration to market Adcirca (tadalafil) to treat pulmonary arterial hypertension (PAH), a high blood pressure disorder affecting the arteries that carry oxygen from the heart to the lungs.

Tadalafil is the active ingredient in the erectile dysfunction drug Cialis. In a news release, United Therapeutics said it was licensing the drug from Cialis' maker, Eli Lilly.

United Therapeutics said Adcirca would be available in August. The drug should not be used in people who take nitrates, commonly prescribed for chest pain. The combination could cause a sudden, dangerous drop in blood pressure, the company said.

PAH -- which has no cure -- has typical symptoms including shortness of breath, fatigue, chest pain and racing heartbeat, according to the U.S. National Institutes of Health. The most common side effects of Adcirca include headache, muscle pain, flushing, respiratory tract infection, nausea, pain in the extremities, upset stomach and nasal congestion.