Herb-Drug Interaction

[Guest guest]

Here is a good piece of text from Michael McIntyre's

website and was featured in The Times:

 

The Times March 05, 2002

 

Risks of drug and herb blend

by Anne Woodham

Recent alerts about taking some prescription medicines with natural

herbs highlights the lack of research into the dangers

 

How safe are herbal medicines? The answer is that nobody knows. The

recent Swedish report on two women on the Pill who became pregnant

after taking St John's wort for mild depression highlights this

issue, particularly as the Medicines Control Agency knows of at

least seven British women in the same situation. One had taken

emergency contraception.

 

And kava, a popular herbal remedy for anxiety, was voluntarily

withdrawn from sale last December by British manufacturers,

retailers and herbalists after German reports of liver damage,

including one death.

 

There is a tendency to think of herbal remedies as " pure "

and " natural " compared with synthetic " toxic " drugs. But if you

think about it, anything that is claimed to have therapeutic powers

is unlikely to be totally inert. In the year 2000 evidence surfaced

that St John's wort could interfere with certain prescription

medicines, including drugs used to treat transplant patients

(cyclosporin), heart conditions and blood clots (warfarin, digoxin),

asthma (theophylline), depression (selective serotonin reuptake

inhibitors — SSRIs) migraine (triptans), HIV infection and the Pill.

 

As a result, all products on sale in the UK carry a label advising

would-be users to seek advice from their pharmacist or doctor if

taking prescription medicine. A flurry of research studies show that

the herb affects enzymes in the liver that control the metabolism of

certain drugs and may result in abnormally high or low levels of

these drugs in the body.

 

But that is only St John's wort. " There is a real lack of research

into drug-herb interactions, " says Dr Jo Barnes, of the Centre for

Pharmacognosy and Phytotherapy at the School of Pharmacy, University

of London. Lists of potential interactions are compiled on the basis

of what is known about the chemical constituents of plants and

conventional drugs. This knowledge is considerable. Dong quai,

feverfew and ginkgo could all theoretically interfere with the

anticoagulant warfarin. Ginseng, if taken with caffeine, could

increase blood pressure. Echinacea can be toxic to the liver and

should not be combined with drugs that can cause liver damage. A

recent study, in Clinical Infectious Diseases, one of the few

carried out so far, found that garlic supplements halved the

effectiveness of the anti-HIV drug saquinavir, valerian is

inadvisable with sedatives and so on.

 

" But it doesn't mean such effects will occur, and if they do, it may

be in only a small proportion of patients and in varying severity, "

says Barnes. " We need to find out. "

 

Professor Edzard Ernst, of the Department of Complementary Medicine

at Exeter University, agrees. " Interactions between herbs and drugs

are a blind spot on the research map, " he says. Neither herbal

manufacturers nor the pharmaceutical companies want responsibility

in what can be a " no-win " situation. " If you search hard enough,

you're bound to find hundreds of interactions, " Ernst adds.

 

Sales of St John's wort fell by more than half in Germany when its

drug interactions were reported, according to Ernst — hardly an

incentive for more research. The UK herbal market, worth around £65

million a year, is remarkably resilient. Holland & Barrett noted a

dip in sales of St John's wort after the adverse publicity, but

these have recovered. Market sources maintain that overall product

sales are stable at worst, increasing by about 5 per cent a year at

best.

 

Despite product warning labels, a recent study carried out by the

School of Pharmacy found that 60 per cent of people buying herbal

remedies in health-food stores had taken them with conventional

drugs. Women tend not to think of either the Pill or herbal remedies

as drugs, so it does not occur to them to seek advice, says Barnes.

And although the Royal College of General Practitioners recommends

that doctors question patients about their use of herbal drugs, most

GPs confess to knowing little about herbal remedies.

 

" Pharmacists are experts on drugs and more aware than most

healthcare professionals of potential interactions with herbal

preparations, " says Barnes. As part of the Yellow Card scheme of

reporting adverse reactions, in 1999 all community pharmacists were

asked to report on over-the-counter and herbal medicines. " It is

important for people to share details about herbal and conventional

medicines they are taking when consulting pharmacists, " says a Royal

Pharmaceutical Society spokesperson.

 

But herbal remedies are often safer than conventional

drugs. " There's evidence that St John's wort has fewer side-effects

than conventional anti-depressants, " says Barnes. Saw palmetto also

has a better safety record and is as effective in treating benign

prostatic hyperplasia as the conventional treatment, finasteride. A

number of trials show that kava can relieve anxiety.

 

But 500mg of paracetamol, or any other pharmaceutical, will be

identical no matter who makes it, while the composition of herbal

products varies according to the manufacturer; the results of a

trial with one product are not applicable to another product

containing the same herb. This is one of the problems bedevilling

the kava controversy.

 

" Different kava products are not chemically equivalent, " says Dr

Dick Middleton, the technical director for Lichtwer Pharma UK, whose

kava product received no reports of adverse reactions. The kava

preparations implicated in liver damage were made by using acetone

to extract the herb's active ingredients such as kavalactones,

according to Michael McIntyre, the chairman of the European Herbal

Practitioners' Association. " When you do that you're leaving out

components such as glutathione, which may protect the liver, " he

says.

 

The McA asked the herbal industry to withdraw kava voluntarily while

the Committee on Safety of Medicines evaluated the situation; a

report is expected this month. Most members have obliged, although

Holland & Barrett has put the herb back on sale. " We heard that kava

had not been withdrawn in Germany because it's not a safety issue, "

says Sharon Flynn, of Holland & Barrett. In response, the McA

says: " We do have concerns that the public may be confused if kava

is on sale in some outlets but not others. "

 

Kava may survive the controversy provided it is manufactured

appropriately, though it is a good example of the difficulties

besetting the market. But much of the concern about the safety,

efficacy and quality of herbal remedies may be removed when the EU's

traditional herbal medicines directive comes into force, perhaps at

the end of this year. This would require manufacturers to register

unlicensed products and produce them according to good

pharmaceutical manufacturing practice.

 

At present many own-brand herbal products are exempt from licensing

and sold as foods under Section 12 (2) of the Medicines Act. Under

the directive, manufacturers would have to prove that herbal

products had been traditionally used for 30 years in the EU, or for

15 years in the EU and for 15 outside it. While this won't cause too

many problems for big European manufacturers, some Chinese and

Ayurvedic products may find difficulty in meeting the requirements.

US imported products, including astragalus, black cohosh and

guaraná, may find the new pharmaceutical standards a challenge.

 

" It's inevitable that consumers will lose out on certain products, "

says Flynn. Nevertheless, many in the herbal industry now feel that

the potential benefits for consumers and the profession will

outweigh the costs.

 

Also, info on legisation in the UK, Ireland and Europe is available

from the same site, www.euroherb.com

 

Attilio

[Guest guest]

"There is a real lack of research into drug-herb interactions,"

 

>>>What is left out is that there is a real lack of research on drug to drug interactions research as well. We really need both as many people are on polypharmacy.

alon

[Guest guest]

I totally agree Alon. TCM practitioers should make an active effect

not only to teach the public about Chinese medicine but also carry

out rigours research into interactions.

 

Attilio

 

, " Alon Marcus "

<alonmarcus@w...> wrote:

> " There is a real lack of research

> into drug-herb interactions, "

>

> >>>What is left out is that there is a real lack of research on

drug to drug interactions research as well. We really need both as

many people are on polypharmacy.

> alon