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Phytother Res. 2018 Jan;32(1):94-102. doi: 10.1002/ptr.5953. Epub 2017 Oct 19.

Acute cardiovascular effects of bitter orange extract (p-synephrine) consumed alone and in combination with caffeine in human subjects: A placebo-controlled, double-blind study.

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Department of Health and Exercise Science, The College of New Jersey, Ewing, NJ, 08628, USA.
School of Pharmacy and Health Professions, Creighton University, Omaha, NE, 68178, USA.


The purpose was to examine cardiovascular responses to supplementation with p-synephrine alone and in combination with caffeine during quiet sitting. Sixteen subjects were given (in double-blind manner) either 103 mg of p-synephrine (S), 233 mg of caffeine +104 mg of p-synephrine (LC + S), 240 mg of caffeine (LC), 337 mg of caffeine +46 mg of p-synephrine (HC + S), 325 mg of caffeine (HC), or a placebo. The subjects sat quietly for 3 hr while heart rate (HR) and blood pressure were measured. Only HC + S and HC significantly increased mean systolic blood pressure (SBP) during the second hour and tended to increase mean SBP during the third hour. Mean diastolic blood pressure in S was significantly lower than the other trials during the first and second hours, and mean arterial pressure was significantly lower in S compared to the LC, LC + S, HC, and HC + S trials. No differences were observed in HR. Consumption of p-synephrine may acutely reduce diastolic blood pressure and mean arterial pressure and not affect SBP or HR during quiet sitting. The addition of p-synephrine to caffeine did not augment SBP or HR indicating that consumption of up to 104 mg of p-synephrine does not induce cardiovascular stress during quiet sitting.


Citrus aurantium; blood pressure; caffeine; heart rate; mean arterial pressure; p-synephrine

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