Herb-Drug Interactions: Cola

Cola acuminata Schott & Endl. or Cola nitida Schott & Endl. (Sterculiaceae)

Synonym(s) and related species

Guru nut, Kola.

Garcinia kola Heckel, Sterculia acuminata Beauv.

Pharmacopoeias

Cola (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4).

Constituents

Cola seed contains xanthine derivatives, mainly caffeine (1.5 to 3%) to which it may be standardised, with traces of theobromine and theophylline. Other constituents include flavonoids from the flavanol group (such as catechin and epicatechin), amines, an anthocyanin pigment (kola red) and betaine.

Use and indications

The main use of cola seed is as a stimulant for depression, tiredness and poor appetite, and as a diuretic. Both uses can be attributed to the caffeine content. Cola is also used as flavouring agent in the manufacture of soft drinks.

Pharmacokinetics

For the pharmacokinetics of caffeine, see caffeine.

For information on the pharmacokinetics of individual flavonoids present in cola, see under flavonoids.

Interactions overview

Cola contains significant amounts of caffeine, therefore the interactions of caffeine, should be applied to cola, unless the product is specified as decaffeinated. By virtue of its caffeine content cola may also cause serious adverse effects if used with other drugs or herbs with similar effects, such as ephedra. Cola may reduce the bioavail-ability of halofantrine and increase the risk of developing hypertension. For information on the interactions of individual flavonoids present in cola, see under flavonoids.

Carbonated cola beverages are acidic, and they can therefore interact with drugs by altering gastric acidity. The best example of this is that they can increase the absorption of the azole antifungal drugs ketoconazole and itraconazole. However, this mechanism is not going to be applicable to herbal medicines containing cola extracts, and these interactions are not therefore covered here.

Cola + Antihypertensives

Cola appears to modestly increase the risk of developing hypertension.

Evidence, mechanism, importance and management

There is a possibility that the effect of cola on blood pressure might differ from that of pure caffeine. There appear to be very few published studies of the effect of cola on blood pressure; however, in the Nurses Health prospective cohort studies, both sugared cola and diet cola beverages were associated with an increased risk of developing hypertension with increased intake. Whether patients taking antihypertensives should limit their intake of cola is unclear. However, the modest hypertensive effects of the caffeine content of cola may be of importance. See Caffeine + Antihypertensives, for further discussion of the adverse effect of caffeine on blood pressure.

Cola + Food

No interactions found. Cola is used as a flavouring in carbonated drinks.

Note that the effects of caffeine from cola-containing herbal medicine or supplement will be additive with those of other caffeine-containing foods or beverages.

Cola + Halofantrine

Cola appears to moderately reduce the bioavailability of halofantrine.

Clinical evidence

In a study in 15 healthy subjects, a single 500-mg dose of halofantrine was given alone or with cola 12.5 g. Cola significantly reduced the maximum concentration and AUC of halofantrine by 45% and 31%, respectively. The overall clearance of halofantrine was reduced by 50%. Similar reductions were seen in the major metabolite of halofantrine, N-desbutylhalofantrine. No adverse effects were reported.

Experimental evidence

No relevant data found.

Mechanism

The authors suggest that caffeine, or other consituents of cola such as catechins or tannins, may have formed a complex with halofantrine to reduce its absorption.

Importance and management

Evidence appears to be limited to this one study, which found a modest reduction in the bioavailabilty of halofantrine. However, the bioavailability of halofantrine can vary widely between patients. Nevertheless, as there is the potential that this interaction could lead to malaria treatment failure, it may be prudent to advise patients to avoid taking cola during treatment with halofantrine.

Cola + Herbal medicines

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