Echinacea (Echinacea spp.)

Traditional texts describe the preparations below, and where those texts give specific amounts, the amounts are quoted here as part of that record. This is a record of historical practice, not a dosage recommendation - the figures are what the sources say, not what HerbMate tells you to take. Amounts, potency, and safe use vary enormously by preparation, plant part, and person.

Theoretically, echinacea may antagonise the effects of immunosuppressants. The use of echinacea has been studied with a number of drugs that are used as probe substrates for cytochrome P450 activity or P-glycoprotein. With the possible exceptions of midazolam and caffeine, no clinically relevant interactions have been identified. Echinacea seems to present a low risk for interactions occurring as a result of these mechanisms.

Herbal medicines

No interactions found.

Immunosuppressants

The interaction between echinacea and immunosuppressants is based on a prediction only.

Tolbutamide

Echinacea does not appear to have a clinically relevant effect on the pharmacokinetics of tolbutamide. In a pharmacokinetic study, 12 healthy subjects were given Echinacea purpurea root 400 mg four times daily for 8 days with a single 500-mg dose of tolbutamide on day 6. The AUC of tolbutamide was increased by 14%, and the time to maximum levels was increased from 4 to 6 hours. The oral clearance was decreased by a mean of 11%, although 2 subjects had a 25% or greater reduction.

Midazolam

Echinacea does not appear to alter the AUC and clearance of oral midazolam, although the bioavailability may be increased. Clearance of intravenous midazolam may be modestly increased in patients taking echinacea. In a pharmacokinetic study, 12 healthy subjects were given Echinacea purpurea root (Nature’s Bounty, USA) 400 mg four times daily for 28 days, with a single 50-microgram/kg intravenous dose of midazolam on day 6 and, 24 hours later, a single 5-mg oral dose of midazolam. The clearance of intravenous midazolam was increased by 42%, and its AUC was reduced by 23%. In contrast, the clearance and AUC of oral midazolam were not significantly altered; however, the oral bioavailability of midazolam was increased by 50% but the oral bioavailability was still relatively low. In another study in 12 healthy subjects given Echinacea purpurea 800 mg twice daily for 28 days with a single 8-mg oral dose of midazolam, there was no difference in the ratio of midazolam to its 1-hydroxy metabolite.

Caffeine

Echinacea appears to have a variable effect on the pharmacokinetics of caffeine. In most patients, echinacea is unlikely to raise caffeine levels. In a pharmacokinetic study, 12 healthy subjects were given an 8-day course of Echinacea purpurea root 400 mg four times daily, with a single 200-mg oral dose of caffeine on day 6. The maximum serum concentration and AUC of caffeine were increased by about 30%. There was a large variation between subjects, with some having a 50% increase in caffeine clearance, and some a 90% decrease. However, the paraxanthine-to-caffeine ratio (a measure of CYP1A2 activity) was reduced by just 10%. In another study in 12 healthy subjects given Echinacea purpurea 800 mg twice daily for 28 days, the paraxanthine-to-caffeine ratio was not significantly affected when a single 100-mg dose of caffeine was given at the end of the treatment with Echinacea purpurea.

Digoxin

Echinacea does not appear to have a clinically relevant effect on the pharmacokinetics of digoxin. In a study, 18 healthy subjects were given an extract containing Echinacea purpurea 195 mg and Echinacea angustifolia 72 mg three times daily for 14 days with a single 250-microgram dose of digoxin before and after the course of echinacea. No significant effects on the pharmacokinetics of digoxin were reported for echinacea, suggesting that echinacea does not have any significant effects on P-glycoprotein. No adverse effects were reported when digoxin was given with echinacea.

Dextromethorphan

Echinacea does not appear to have a clinicall In a study, 12 healthy subjects were given Echinacea purpurea root 400 mg four times daily for 8 days with a single 30-mg dose of dextromethorphan on day 6. In the 11 subjects who were of the cytochrome P450 isoenzyme CYP2D6 extensive metaboliser phenotype there were no changes in the pharmacokinetics of dextromethorphan. In contrast, the one subject who was a poor metaboliser had a 42% increase in the AUC of dextromethorphan and a 31% increase in its half-life. In another study, in 12 healthy subjects given Echinacea purpurea 800 mg twice daily for 28 days, there was no change in the debrisoquine urinary ratio after a single 5-mg dose of debrisoquine.

Food

No interactions found.

These entries keep the wording of the reference they come from, and three phrases mean three different things. "No interactions found" means the source looked for reports of that pairing and found none. "No data found" means nothing has been published either way. "Based on experimental evidence only" means the effect has been seen in a laboratory or animal study but not in people - a reason for caution, not a report of harm.