Energy
p-Synephrine
p-Synephrine is a bitter orange stimulant with inconsistent pre-workout evidence and unsettled dose safety.
- Clinical dose
- 20–50 mg
- Safety ceiling
- 50 mg
- Evidence
- weak
- Category
- Energy
Evidence summary
Research confidence: medium
Human pre-workout evidence is inconsistent. A typical 20 mg dose added no measurable benefit to a caffeinated pre-workout; isolated signals for muscular endurance or fat oxidation came from small studies using about 100 mg or 2-3 mg/kg. Those metabolic findings do not establish better overall workout performance, and no universally accepted safe supplemental dose exists.
Research sources
- The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p-Synephrine: A Systematic Review and Meta-Analysis(opens in new window)
- Bitter Orange: Usefulness and Safety (NIH NCCIH)(opens in new window)
NIH concludes that bitter orange has not been clearly shown helpful for any health purpose, most athletic-performance studies found no benefit, and cardiovascular safety evidence is inconclusive.
- Pre-workout with and without 20 mg p-synephrine (JISSN, 2017)(opens in new window)
Adding 20 mg p-synephrine to a pre-workout containing 284 mg caffeine produced limited to no additive benefit for lifting volume, Wingate performance, or cognitive outcomes.
- p-Synephrine and resistance-exercise performance (JISSN, 2015)(opens in new window)
A small trial in 12 men reported more squat repetitions at 100 mg, but the ingredient manufacturer funded the study and one author consulted for the company.
- Risk assessment of synephrine (Netherlands RIVM)(opens in new window)
RIVM could not derive a safe supplemental dose and warns that caffeine and physical activity may magnify synephrine's effects.