THURSDAY, Feb. 27, 2020 (HealthDay News) — For patients with refractory chronic cough or unexplained chronic cough, the P2X3 receptor antagonist gefapixant 50 mg twice daily significantly reduces cough frequency, according to a study published online Feb. 25 in The Lancet Respiratory Medicine.

Jaclyn A. Smith, Ph.D., from the University of Manchester in the United Kingdom, and colleagues conducted a phase 2b trial involving adults with refractory or unexplained chronic cough. Participants were randomly assigned to receive either placebo or 7.5, 20, or 50 mg oral gefapixant twice daily for 84 days (63, 64, 63, and 63 participants, respectively).

The researchers found that patients’ geometric mean awake cough frequency was 18.2 coughs per hour with placebo at 12 weeks compared with 14.5, 12.0, and 11.3 coughs per hour with 7.5, 20, and 50 mg gefapixant, respectively. Relative to placebo, the estimated percentage change was −22.0 percent (95 percent confidence interval [CI], −41.8 to 4.6; P = 0.097), −22.2 percent (95 percent CI, −42.0 to 4.3 percent; P = 0.093), and −37.0 percent (95 percent CI, −53.3 to −14.9; P = 0.0027) with 7.5, 20, and 50 mg gefapixant, respectively. The most common adverse event was dysgeusia.

“We look forward to the results of the phase 3 trials that are underway before we know the true degree of efficacy of the 50 mg dose of gefapixant in controlling unexplained chronic cough and whether the associated taste-related adverse events are tolerable,” write the authors of an accompanying editorial.

The trial was funded by Afferent Pharmaceuticals (since acquired by Merck), which manufactures gefapixant and funded the study.

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