Synephrine, also known as phenylephrine, is a stimulant substance belonging to the group of sympathomimetics, which affects the nervous system and metabolism. It is naturally present in certain plants, such as mustard or bitter orange (Citrus aurantium). Synephrine is also used as an ingredient in dietary supplements and weight loss products.

Thermogenic fat burners belong to the category of stimulant-based fat burners. They work by stimulating the central nervous system and slightly increasing body temperature, which is so subtle that it is barely noticeable but crucial for kickstarting fat burning. As a result, they also accelerate metabolism. They typically contain various combinations of active ingredients combined with caffeine. Due to this, they can affect blood pressure and heart rate, and it is important to have good overall health before using them.