FDA bans dietary supplements containing ephedrine alkaloids

In 2004 the US Food and Drug Administration banned dietary supplements containing ephedrine alkaloids, citing serious effects on the heart ^[1]. The weight-loss supplement industry did not disappear. Instead, many weight-loss and bodybuilding products replaced ephedra with bitter orange (Citrus aurantium) plus caffeine ^[1]. Bitter orange contains synephrine, a chemical that acts similarly to ephedra ^[1].

Researchers then tested whether the "ephedra-free" replacements behaved differently. A study published in September 2005 in The American Journal of Medicine enrolled 10 healthy adult nonsmokers in a randomized, double-blind, placebo-controlled, three-arm crossover trial with a one-week washout between single doses ^[2]. Participants were five men and five women, ages 19 to 42, average age 27 ^[2].

The three treatments were Advantra Z, a C. aurantium product containing 46.9 mg of synephrine; Xenadrine EFX, a multi-ingredient formula containing 5.5 mg of synephrine; and placebo ^[2]. Compared with placebo, Xenadrine EFX raised blood pressure, with peak changes from baseline at 2 hours of 9.6 mm Hg systolic (P = 0.047) and 9.1 mm Hg diastolic (P = 0.002) ^[2]. Heart rate rose at 6 hours by 16.7 beats per minute with Xenadrine EFX (P = 0.011) and 11.4 beats per minute with Advantra Z (P = 0.031) ^[2]. No adverse events occurred during the study ^[2].

Notably, Advantra Z did not raise blood pressure even though it delivered roughly eight times more synephrine ^[2]. The authors concluded that the effects were not likely caused by C. aurantium alone and may be attributable to caffeine and other stimulants in the multi-component formulation, and that reformulated weight-loss supplements have "similar acute cardiovascular stimulant actions" to the banned ephedra products ^[2]. Two of the study authors disclosed that they had served as paid expert witnesses in litigation involving dietary supplement manufacturers ^[2].

Why it matters for patients

Anyone shopping for weight loss today still encounters over-the-counter stimulant "fat burners" on the same shelves and websites as information about prescription options. The 2004 ban shows that removing one ingredient does not necessarily change the category: a chemically similar stimulant took its place within months ^[1].

WebMD's monograph says bitter orange is likely safe in food amounts but possibly unsafe in the larger amounts used as medicine, and that taking it alone or with stimulants such as caffeine might increase the risk of high blood pressure, fainting, heart attack, stroke and other serious side effects, as well as headaches, including migraines and cluster headaches ^[1]. It lists specific cautions for people with high blood pressure, glaucoma, irregular heartbeat and long QT interval syndrome, and says bitter orange should be stopped at least two weeks before scheduled surgery because it can raise heart rate and blood pressure ^[1].

There are also documented interactions: with MAOI antidepressants such as phenelzine, selegiline and tranylcypromine; with other QT-prolonging drugs; with stimulant drugs; and with diabetes medications, because bitter orange might lower blood sugar ^[1]. Bitter orange can also slow how the liver clears drugs including dextromethorphan, felodipine, indinavir, midazolam, sildenafil and colchicine ^[1].

Label accuracy is a separate issue. Products containing synephrine have been found to contain amounts much higher than what the label lists, and also to contain other synthetic stimulants that are banned in supplements ^[1]. Synephrine is a banned substance under National Collegiate Athletic Association rules ^[1].

What is still unknown

The 2005 trial tested single doses in 10 healthy young adults and tracked effects over hours ^[2]. It does not answer how these products affect blood pressure or heart rhythm over weeks or months, or in people who already have heart disease. WebMD states that bitter orange is used for obesity and athletic performance "but there is no good scientific evidence to support its use" ^[1].

The sources here do not compare stimulant supplements with prescription GLP-1 medicines such as semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound), and they do not address whether people use both at the same time. That question is not answered by this research.