Ginseng abuse syndrome (hypertension, nervousness, insomnia, morning diarrhea, inability to concentrate and skin reactions) has been reported and there has been a report of a 28-year-old woman who had a severe headache after ingesting a large quantity of ethanol-extracted ginseng. Cerebral angiograms showed ‘beading’ appearance in the anterior and posterior cerebral and superior cerebellar arteries, consistent with cerebral arteritis. High doses (1 5 g/day) have been associated with confusion, depression and depersonalisation in four patients.
However, the majority of the scientific data suggest that ginseng is rarely associated with adverse events or drug interactions. A systematic review found that the most commonly experienced adverse events are headache, sleep and gastrointestinal disorders. Data from clinical trials suggest that the incidence of adverse events with ginseng mono-preparations is similar to that of placebo. Any documented effects are usually mild and transient. Combined preparations are more often associated with adverse events, but causal attribution is usually not possible.
A case of suspected ginseng allergy has recently been reported in the scientific literature. The case involved a 20-year-old male who developed urticaria, dyspnoea and hypotension after ingesting ginseng syrup. The subject recovered fully and was discharged after 24 hours.
Ginseng has very low toxicity. Subacute doses of 1.5-15 mg/kg of a 5:1 ginseng extract did not produce negative effect on body weight, food consumption, haematological or biochemical parameters, or histological findings in dogs and no effects have been observed from the administration of similar doses in two generations of rat offspring.
Traditionally, ginseng is not recommended with other stimulants such as caffeine and nicotine and a case report exists of a 39-year-old female experiencing menometrorrhagia, arrhythmia and tachycardia after using oral and topical ginseng along with coffee and cigarettes.
Ginseng may increase the clearance of alcohol from the blood according to an open trial of 14 healthy volunteers — beneficial interaction possible.
CHEMOTHERAPY, RADIOTHERAPY AND GENERAL ANAESTHETICS
Preliminary evidence suggests that Panax ginseng saponins may reduce nausea and vomiting associated with chemotherapy, radiotherapy and general anaesthetics by antagonising serotonin (5-hydroxytryptamine, 5HT) type 3A receptors. Ginseng may also help to sensitise cancer cells to chemotherapeutic agents according to preliminary evidence.
Ginseng contains glycosides with structural similarities to digoxin which may modestly interfere with digoxin results. These naturally occurring glycosides may cause false elevation of fluorescence polarisation and falsely low microparticle enzyme results, although Tina-quant results appear unaffected. There are no confirmed case reports of actual interaction.
DRUGS METABOLISED CHIEFLY BY CYP1A AND CYP2D6
Mixed reports exist as to whether ginseng may act as an inhibitor of cytochrome CYP1A or CYP2D6 and if so whether the effect is likely to be clinically significant. Observe for increased drug bioavailability and clinical effects.
Ginseng increased the mean plasma concentration of the calcium channel blocker nifedipine by 53% at 30 minutes in an open trial of 22 healthy subjects. Effects at other time points were not reported. Caution.
In animal studies the combination of ginseng polysaccharides with vancomycin resulted in a 100% survival rate for animals treated for Staphylococcus aureus compared to only 57% or 50% survival in animals treated with ginseng polysaccharides or vancomycin alone. A beneficial additive effect is possible but clinical use in humans has not yet been established.
No affects on the pharmacokinetics or pharmacodynamics of either S-warfarin or R-warfarin were revealed in an open-label, crossover randomised trial of 12 healthy male subjects who received a single 25-mg dose of warfarin alone or after 7 days’ pretreatment with ginseng. Whether these effects are consistent in less ‘healthy’ people likely to be taking warfarin or for prolonged concurrent use is unclear.
There have been two case reports of ginseng reducing theantithrombotic effects of warfarin. Additionally, it inhibits platelet aggregation according to both in vitro and animal studies. Avoid using this combination unless under medical supervision to monitor antithrombotic effects.