Efficacy and safety of clemastine-pseudoephedrine-acetaminophen versus pseudoephedrine-acetaminophen in the treatment of seasonal allergic rhinitis in a 1-day, placebo-controlled park study.

BACKGROUND: Allergic rhinitis afflicts more than 40 million people in the United States and is a leading cause of reduced productivity at work and in school. Patients with allergic rhinitis have a wide range of symptoms that are often treated with oral combination products that contain antihistamines, decongestants, and analgesics.

OBJECTIVE: To evaluate the onset of action and the extent of efficacy and safety of a combination (CPA) of clemastine (0.68 mg), pseudoephedrine (60 mg), and acetaminophen (1,000 mg) versus a combination (PA) of pseudoephedrine and acetaminophen versus placebo in the treatment of seasonal allergic rhinitis (SAR). The primary goal was to evaluate the benefit of adding clemastine to the PA combination product to treat the symptoms of SAR.

METHOD: A 1-day, multicenter, double-blind, double-dummy, randomized, parallel-group park study was organized, and medication was given at 9:00 AM and 3:00 PM.

RESULTS: A total of 298 subjects participated at two outdoor facilities. The primary efficacy outcome was the major symptom complex score averaged over the period of 2 to 5 hours after each dose. Mean absolute and percentage reduction in major symptom complex averaged over the period of 2 to 5 hours in the CPA group was significantly superior to those of either the PA (P < 0.01) or placebo (P < 0.03) groups. Somnolence, fatigue, and nausea were the most common volunteered adverse events; only somnolence was significantly greater after CPA than after either PA or placebo.

CONCLUSIONS: Treatment with CPA was safe and highly effective in reducing symptoms associated with SAR. It was more effective than either PA or placebo over most of the postdose observation period.