Absence of QTc-interval-prolonging or hemodynamic effects of a single dose of bitter-orange extract in healthy subjects

Pharmacotherapy. 2005 Dec;25(12):1719-24. doi: 10.1592/phco.2005.25.12.1719.


Study objective: To evaluate the hemodynamic and electrocardiographic effects of a single dose of commercially available bitter-orange dried-fruit extract, which is increasingly being used in dietary supplements.

Design: Randomized, double-blind, placebo-controlled, crossover study.

Setting: University of Connecticut, Storrs Campus.

Subjects: Eighteen healthy volunteers aged 18 years or older.

Intervention: Subjects were given either placebo or bitter-orange dried-fruit extract (450 mg standardized to 27 mg of m- or p-synephrine) in phase 1. The opposite treatment was given during phase 2 after a washout period of at least 7 days.

Measurements and main results: The rate-corrected QT (QTc) interval and blood pressure were measured before dosing and at 1, 3, 5, and 8 hours after dosing. Mean+/-SD values of the maximum postdose values were compared between groups. Subjects receiving bitter-orange extract versus those receiving placebo had similar postdose QTc intervals (402+/-29 vs 403+/-24 msec, p=0.653), systolic blood pressure (114+/-10 vs 115+/-8 mm Hg, p=0.686) and diastolic blood pressure (68+/-9 vs 68+/-8, p=0.879).

Conclusion: Bitter-orange dried-fruit extract standardized to m- or p-synephrine 27 mg did not significantly alter the QTc interval or blood pressure after a single dose was administered. Future studies are necessary to ensure the safety of this herbal product with multiple doses.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-Obesity Agents / adverse effects*
  • Citrus / chemistry*
  • Cross-Over Studies
  • Double-Blind Method
  • Electrocardiography / drug effects*
  • Female
  • Fruit
  • Hemodynamics / drug effects*
  • Humans
  • Male
  • Plant Extracts / adverse effects


  • Anti-Obesity Agents
  • Plant Extracts