The US Food and Drug Administration (FDA) has approved tenapanor (Ibsrela, Ardelyx) tablets for the treatment of irritable bowel syndrome with constipation (IBS-C) in adults. The recommended dosage is 50-mg twice daily, taken immediately before breakfast or the first meal of the day and immediately before dinner. Tenapanor is a minimally-absorbed small molecule that acts locally in the gastrointestinal (GI) tract to inhibit the sodium-hydrogen exchanger NHE3, resulting in an increase in bowel movements and a decrease in abdominal pain in patients with IBS-C, the company explains in a news release. Tenapanor was evaluated in two randomized, double-blind, placebo-controlled trials. Both trials demonstrated a statistically significant reduction in constipation and abdominal pain in adults with IBS-C. The most common adverse event was diarrhea (16% with tenapanor vs 4% with placebo in trial 1; and 15% with tenapanor vs 2% with placebo in trial 2). Severe diarrhea was reported in 2.5% of tanapanor-treated patients compared with 0.2% of placebo-treated patients during the 26 weeks of trial 1 and the 12 weeks of trial 2. Overall discontinuation rates were low among patients treated with tenapanor (7.6%) and placebo (0.8%). Diarrhea was the most common adverse reaction leading to discontinuation (6.5% of tenapanor-treated patients compared with 0.7% of placebo-treated patients). If severe diarrhea occurs, tenapanor should be stopped and the patient rehydrated, the prescribing information states. Tenapanor is contraindicated in patients with known or suspected mechanical gastrointestinal obstruction. The safety and effectiveness of tenapanor have not been established in pediatric patients younger than age 18 years. Source
