Herb-Drug Interactions: Elder

2011

Sambucus nigra L. (Caprifoliaceae)

Synonym(s) and related species

Black elder, European elder, Sambucus.

Not to be confused with American elder, which is Sambucus canadensis L.

Pharmacopoeias

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

Constituents

The flowers and berries of elder are most often used medicinally. The flowers contain: triterpenes based on oleanolic and ursolic acids; the flavonoids rutin, quercetin, hyperoside, kaempferol, nicotoflorin and others; and linolenic and linoleic acids. The berries contain: anthocyanins cyanidin-3-sambubioside and cyanidin-3-glucoside; the flavonoids quercetin and rutin; cyanogenic glycosides including sambunigrin; and vitamins. The unripe berries of elder contain toxic constituents, but these are lost on drying and/or heating, and are not present in the medicinal product. Elder extracts may be standardised to contain 0.8% flavonoids based on isoquercitroside (British Ph 2009, European Ph, 6th ed., 2008 and Supplements 6.1, 6.2, 6.3 and 6.4).

Use and indications

Elder extracts are used mainly to treat colds and flu. Several in vitro studies have shown that elder berry constituents have antidiabetic, antiviral and immune-modulating effects, enhance cytokine production and activate phagocytes, but clinical data are lacking.

Pharmacokinetics

No relevant pharmacokinetic data found. For information on the pharmacokinetics of individual flavonoids found in elder, see under flavonoids.

Interactions overview

There is some very weak experimental evidence to suggest that elder extracts may have additive effects with antidiabetic drugs and phenobarbital, and may antagonise the effects of morphine. For information on the interactions of individual flavonoids found in elder, see under flavonoids.

Elder + Antidiabetics

The interaction between elder and antidiabetics is based on experimental evidence only.

Clinical evidence

No interactions found.

Experimental evidence

In an in vitro study, it was found that an aqueous elder flower extract enhanced glucose uptake by 70%, but had no additional effect on glucose uptake when insulin was also given. The extract also stimulated insulin secretion and glycogen synthesis.

Mechanism

Elder is thought to enhance insulin secretion in a similar manner to the sulphonylureas. This study supports this suggestion as it found that diazoxide inhibited the effects of elder.

Importance and management

The in vitro study provides limited evidence of a possible blood-glucose-lowering effect of an aqueous elder flower extract. Because of the nature of the evidence, applying these results in a clinical setting is extremely difficult, and the effect of elder flower extracts given with conventional antidiabetic medication is unknown. However, if patients taking antidiabetic drugs want to take elder it may be prudent to discuss the potential for additive effects, and advise an increase in blood-glucose monitoring, should an interaction be suspected.

Elder + Food

No interactions found.

Elder + Herbal medicines

No interactions found.

Elder + Morphine

The interaction between elder and morphine is based on experimental evidence only.

Clinical evidence

No interactions found.

Experimental evidence

In a study in rats aqueous extracts of elder flower and elder berry were found to modestly decrease the analgesic effects of morphine 90 minutes after dosing. The elder extracts had no effect on the analgesic response to morphine at a subsequent time point (150 minutes), and had tended to increase the effects of morphine 10 minutes after dosing. The berry and flower extracts had no analgesic effect when given alone.

Mechanism

Unknown.

Importance and management

Evidence for an interaction between extracts of elder flower and elder berry and morphine appears to be limited to this study in rats, which found only a modest decrease in analgesic effects at just one time point. It is unknown if this effect would occur in humans, but, even if it does, it seems unlikely to be of much clinical relevance.

Elder + Phenobarbital

The interaction between elder and phenobarbital is based on experimental evidence only.

Clinical evidence

No interactions found.

Experimental evidence

In a study in rats aqueous extracts of elder flower and elder berry were found to approximately halve the time to the onset of sleep and increase the sleeping time in response to phenobarbital (from about 190 minutes to 200 minutes).

Mechanism

Unknown.

Importance and management

Evidence for an interaction between extracts of elder flower and elder berry and phenobarbital appears to be limited to this study in rats, which found only a very modest increase in sleeping time. It is unknown if this effect would occur in humans, but, even if it does, it seems unlikely to be clinically relevant.