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COMPLEMENTARY AND ALTERNATIVE MEDICINE

Blood Pressure and Heart Rate Effects Following a Single Dose of Bitter Orange

at time of study, PharmD Student, School of Pharmacy, University of California, San Francisco, CA; now, Pharmacy Practice Resident, Long Beach Memorial Medical Center, Long Beach, CA

DiemThuy T Nguyen, PharmD

at time of study, PharmD Student, School of Pharmacy, University of California, San Francisco; now, Pharmacy Practice Resident, Long Beach Memorial Medical Center

Peter J Ambrose, PharmD FASHP

Professor of Clinical Pharmacy and Vice Chair, Department of Clinical Pharmacy, School of Pharmacy, University of California, San Francisco; Department of Pharmacy Services, Long Beach Memorial Medical Center

Reprints: Dr. Ambrose, Department of Pharmacy Services, Long Beach Memorial Medical Center, 2801 Atlantic Ave., PO Box 1428, Long Beach, CA 90801-1428, fax 562/933-2348, pambrose{at}memorialcare.org

BACKGROUND: The ingredients of numerous "ephedra-free" dietary supplements used for weight loss include bitter orange, which contains sympathomimetic alkaloids such as synephrine. Due to the similarity in chemical structure to ephedrine and the potential sympathomimetic effects of synephrine, it is hypothesized that bitter orange may increase blood pressure (BP) and heart rate (HR).

OBJECTIVE: To determine the effects on BP and HR after a single dose of bitter orange in healthy adults.

METHODS: In a prospective, randomized, double-blind, placebo-controlled, crossover study, 15 young, healthy, adult subjects received either a single dose of Nature's Way Bitter Orange—a 900 mg dietary supplement extract standardized to 6% synephrine—or matching placebo, with a one week washout period. Systolic BP (SBP), diastolic BP (DBP), and HR were measured at baseline and every hour for 6 hours after administration.

RESULTS: SBP after bitter orange was significantly increased versus placebo at hours 1-5 (p < 0.0001); the peak difference was 7.3 ± 4.6 mm Hg. Although the baseline DBP was higher than after administration of both placebo and bitter orange, DBP after bitter orange was significantly increased versus placebo at hours 4 and 5 (p 0.02); the peak difference was 2.6 ± 3.8 mm Hg. HR was significantly increased after bitter orange versus placebo for hours 2-5 (p < 0.01); the peak difference was 4.2 ± 4.5 beats/min.

CONCLUSIONS: SBP, DBP, and HR were higher for up to 5 hours after a single dose of bitter orange versus placebo in young, healthy adults.

Key Words: bitter orange, blood pressure, dietary supplements, heart rate, synephrine

Published Online, November 29, 2005. www.theannals.com, DOI 10.1345/aph.1G488