Butterbur (Petasites hybridus) has been used to relieve headaches for centuries. But the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has decided to pull all butterbur products from the UK market, on what appears to be extremely flimsy evidence. What’s going on?

Butterbur: a “serious risk” to health

Back in January this year, the UK’s medicines regulator sent a letter to herbal representatives asking them to voluntarily withdraw all unlicensed butterbur products from the UK market – which meant all food supplements, since no butterbur product has yet been registered under the Traditional Herbal Medicinal Products Directive (THMPD). It also warned consumers that, “Butterbur products have been associated with [40] cases of liver toxicity [in the literature]. Of these cases, nine were of acute hepatitis and two of the nine cases resulted in liver failure requiring transplantation.” 

The long arm of Ron Law

While researching the relative risk of death associated with food supplements and other substances and activities, consultant Ron Law asked the MHRA for its scientific justification behind the butterbur decision. The MHRA responded by sending him a copy of a paper by Anderson et al [1], which the MHRA had helpfully highlighted in order to show its reasoning.

Flimsy evidence

Here are the key reasons why the MHRA decided to remove all butterbur products from UK shelves:

  1. In its warning to consumers, the MHRA states that, “40 cases have been reported in the literature”.  As it happens, the Anderson et al paper mentions these cases [1], which occurred outside the UK, but the MHRA itself is apparently unable to locate any original records relating to them.  As such, the MHRA’s claim cannot be validated
  2. The paper also refers to minor changes to liver duct structure that occurred during a 6-month toxicity study of Petadolex in rats [1] given a Petadolex dose equivalent to 60–100 times the maximum clinical dose!
  3. It refers as well as to mild to moderate increases in liver enzyme levels in a 28-day rat toxicity study, at doses equivalent to 200–300 times the maximum clinical dose
  4. Finally, the paper notes that reductions were observed in the levels of bile salt transporters in an in vitro experiment using human liver cells exposed to extracts containing different concentrations of one of butterbur’s active chemicals

Scientific fraud

So, it appears that the MHRA has pulled butterbur based on the findings of a single paper, not waiting for them to be expanded upon or even repeated. A paper, moreover, that reported potential toxicity in rat studies and test-tube experiments – so-called ‘preclinical’ studies that, as likely as not, are completely unrelated to what would happen in living, breathing human beings. Not to mention that those experiments used doses enormously in excess of anything a person taking Petadolex, or any other butterbur-containing product, will ever receive in real life. Nowhere does the MHRA appear to have considered that people have been using butterbur for centuries to manage headache, or even that its use is associated with significant benefits – only supposed risks.

Butterbur isn’t banned

But the MHRA still hasn't added butterbur to the list of prohibited herbs in the UK, so, as yet, it's not officially a banned herb. It seems butterbur may be being used as another scapegoat to justify further clampdowns on herbs, something we’ve been expecting as the UK’s ‘sell-through’ of unlicensed herbal products phases out.

Herbs – and food supplements – are safe

As we demonstrated last week, herbal products and food supplements are among the safest substances we consume. Yet, here we have products being removed from the market using a level of precaution that is simply ridiculous — while completely ignoring any benefits that consumers of those products might receive. Obviously, if the MHRA applied the same over-precautionary principle to mainstream medicines, not a single one would remain on the market!

Oddly enough, we can’t see that happening.

Call to action

  • Share this article widely and raise awareness of this insidious use of scare tactics on the part of regulators. Butterbur has not been banned – the evidence is too flimsy – but consumers and suppliers are being bullied by fearmongering. This is a picture we're seeing all over Europe, and it's clear that competent authorities in Member States do not have sufficient understanding about the use of botanicals
  • If you reside in the UK, you are still legally entitled to source butterbur from outside the country for personal use while it remains off a banned list. It's sad to undermine the UK herbal industry in this way, but many people have used butterbur safely for centuries, and should continue to be able to do so within normal, safe, doses. Send a message to the authorities that we won't be bullied in this way – and keep buying your butterbur!
  • Refer to a professional herbal practitioner for more detailed information on butterbur
  • Use our comment facility to share your stories and experiences of using butterbur


[1] Anderson N et al. Toxicogenomics applied to cultures of human hepatocytes enabled an identification of novel Petasites hybridus extracts for the treatment of migraine with improved hepatobiliary safety. Toxicol Sci 2009;112:507–20.


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