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FDA Approves Tenapanor for IBS-C

On September 12, Ardelyx, Inc. announced that its new medication for IBS-C, tenapanor (Ibsrela), received approval from the U.S. Food and Drug Administration (FDA).1 Ibsrela is only approved for adults ages 18 years and older. The recommended dose for adults is a 50 mg tablet taken twice daily, immediately before breakfast or the first meal of the day and immediately before dinner.2

The approval comes after data from the Phase III T3MPO-2 and T3MPO-1 trials. The studies looked at the number of people who responded to the 12-week treatment period.1 This included those who reported a 30 percent decrease in a weekly average abdominal pain score compared with how they ranked their pain at the beginning of the trials, and an increase of at least one spontaneous bowel movement in a weekly average compared to the beginning of the trial, in the same week, for at least six of the first 12 treatment weeks.1

Ardelyx is also testing tenapanor for hyperphosphataemia in end-stage renal disease for people on dialysis. Data were released earlier this month from the Phase III Amplify study, showing that people on the medication met treatment goals compared with placebo.1

How it works and side effects

In each of the studies, people who took tenapanor showed improvements in abdominal pain compared with the placebo.1 Tenapanor works by blocking the NHE3 transporter in the gastrointestinal tract, which increases sodium in the gut.2 This increases fluid in the gut, which loosens stool and helps to relieve constipation for people with IBS.

Data collected from 1,203 adults with IBS-C in two trials show the most common side effects are diarrhea, abdominal distension, flatulence, and dizziness.2 However, these adverse reactions were reported in at least two percent of people treated with tenapanor, which was similar to treatment with placebo.

Of those 1,203 people in placebo-treated trials of tenapanor, 100 (or 8 percent) were 65 years of age and older.2 There are no differences in the efficacy of the medication between elderly and younger individuals with IBS-C. However, increased sensitivity cannot be ruled out among elderly individuals.2

  1. Ardelyx receives FDA approval for Ibsrela® (tenapanor), an NHE3 sodium transport inhibitor, for the treatment of irritable bowel syndrome with constipation. Ardelyx, Inc. Available at: Published September 12, 2019. Accessed September 13, 2019.
  2. Highlights Of Prescribing Information. Ardelyx, Inc. Available at: Published September 2019. Accessed September 13, 2019.