Herb-Drug Interactions: Guarana

Paullinia cupana Kunth (Sapindaceae)

Synonym(s) and related species

Brazilian cocoa. Paullinia sorbilis.

Constituents

Guarana seeds contain xanthine derivatives; principally caffeine (also known as guaranine, up to 7%), with theobromine, theophylline and others, and small amounts of flavonoids, from the flavanol group, such as catechin. Other constituents include saponins and an essential oil containing estragole and anethole.

Use and indications

The main use is as a tonic or stimulant for tiredness and to promote alertness, which can be attributed to the caffeine content.

Pharmacokinetics

The pharmacokinetics of caffeine are discussed under caffeine.

Interactions overview

Guarana contains significant amounts of caffeine, therefore the interactions of caffeine, are relevant to guarana. Two case reports describe muscular disorders, which were related to the use of guarana-containing herbal supplements. For mention of a study in which a herbal supplement containing guarana and black tea, among other ingredients, slightly increased blood pressure, see Tea + Antihypertensives.

Guarana + Antihypertensives

For mention of a study in which a herbal supplement containing guarana and black tea, among other ingredients, slightly increased blood pressure, see Tea + Antihypertensives.

Guarana + Food

No interactions found; however, the effects of caffeine from herbal medicines or supplements containing guarana and caffeine-containing foods or beverages will be additive.

Guarana + Herbal medicines

Two case reports describe muscular disorders in patients who took supplements containing guarana and ephedra, and guarana and kava.

Evidence, mechanism, importance and management

A case report describes a 54-year-old woman, with no significant medical history, who developed rhabdomyolysis after she started to take guarana 190mg and ephedra 150mg (containing ephedrine 12 mg), with other dietary supplements. The creatine kinase elevations resolved within 3 weeks of stopping the herbal weight-loss supplement. The authors of this report suggest that, as guarana contains caffeine alkaloids, this and the combination of ephedrine effects may have contributed to the myopathy. Another case describes myoglobinuria in a patient taking a supplement containing guarana, ginkgo and kava. Again, this was thought to be related to the combined effects of guarana and other herbal medicines, in this case, kava.

The general importance of these cases is unclear, and many patients taking drugs that are known to cause muscle damage such as the statins, frequently take caffeine, which is found in guarana, food or beverages.

The caffeine content of guarana suggests that it may interact with other herbal medicines in the same way as caffeine, see Caffeine + Herbal medicines; Bitter orange, and Ephedra + Caffeine.