I was prescribed ivy leaf extract for my (quite heavy) cough.
Does it work, or is it just a placebo?
TL;DR: While there have been individual studies, mostly of low quality, the systematic reviews suggest the evidence is poor.
The first port of call for medical claims, Cochrane Reviews, has nothing on ivy, which is a shame.
I notice in the studies I did find, a strong bias towards being produced in Germany, which raises my eyebrow.
"Cough" is a broad term. I found studies looking at bronchitis and studies looking at asthma.
Summary: I found a total of four studies supporting the use of Ivy leaf extract: one poor, two very poor and one that seemed reasonable. Finally, I found a recent systematic review of te evidence that suggested that there is still reasonable doubt about its effectiveness.
The first positive study I looked at was Ivy versus Ambroxol in chronic bronchitis, J. Meyer-Wegener, K. Liebscher and M. Hettich. Allgemeinmedizin, Vol. 3, p. 61-66 31 January 1993. It was a randomised, controlled, double-blind test comparing a commercial treatment based on Ivy leaf extract to a control of another drug, Ambroxol, and found they were equivalent. This is only useful if Ambroxol is, indeed, the best-in-class alternative treatment. If Ambroxol is ineffective as a treatment, then this trial proves the ivy-based pill is equally ineffective. The paper does include references to older papers which, it claims, provide a mechanism to explain Ivy leaf's actions.
The next trial I found was a joke: Open Trial to Assess Aspects of Safety and Efficacy of a Combined Herbal Cough Syrup with Ivy and Thyme, Büechi S, Vögelin R, von Eiff MM, Ramos M, Melzer J, Forsch Komplementärmed Klass Naturheilkd 2005;12:328-332 (DOI: 10.1159/000088934) The control used was just the baseline symptoms at the start of the trial. Surprise, surprise, people didn't cough as much twelve days (on average) later. The fact that the journal published this tripe reflects poorly upon it.
Oh dear, I have just noticed the third study was published in the same journal, three years earlier. Treatment of chronic bronchitis with ivy leaf special extract--multicenter post-marketing surveillance study in 1,350 patients Hecker M, Runkel F, Voelp A. Forsch Komplementärmed Klass Naturheilkd. 2002 Apr;9(2):77-84. It suffers from exactly the same problem - the control was the baseline, four weeks earlier.
Bronchitis is often self-limiting. If you wait four weeks, most patients will report their symptoms have improved, even if the drugs do nothing.
The fourth study had a defensible positive result! :-)
Efficacy and tolerability of a fluid extract combination of thyme herb and ivy leaves and matched placebo in adults suffering from acute bronchitis with productive cough : A prospective, double-blind, placebo-controlled clinical trial KEMMERICH Bernd; EBERHARDT Reinhild; STAMMER Holger
I perused the abstract, and I couldn't see anything obviously wrong with this approach. They include Thyme in the mix which may or may not be relevant. The journal in which it is published is fairly low impact.
Finally, I discovered Systematic Review of Clinical Trials Assessing the Effectiveness of Ivy Leaf (Hedera Helix) for Acute Upper Respiratory Tract Infections, Evidence-Based Complementary and Alternative Medicine, Volume 2011 (2011), Article ID 382789, doi:10.1155/2011/382789 Review Article.
They reached a similar conclusion to me (with far more rigour!):
They do go on to suggest that the other popular cough medicines are also not evidence-based, and the alternative of prescribing antibiotics for uncomplicated Upper Respiratory Tract Infections (URTI) is undesirable.
That raises an interesting ethical point: if you have a culture amongst patients that demands from doctors that medicines be prescribed, is it ethically acceptable for a busy doctor to prescribe a possibly ineffective treatment that is well-tolerated, rather than to prescribe antibiotics or to spend the time educating them on self-limiting ailments?
We seem to have some real science here!
First, a general review in 2000 of herbal medicines:
Herbal medicines for asthma: a systematic review, A Huntley, E Ernst,Thorax 2000;55:925-929 doi:10.1136/thorax.55.11.925
Then a review of ivy leaves in particular for children:
Efficacy of dry extract of ivy leaves in children with bronchial asthma – a review of randomized controlled trials, D. Hofmanna, M. Heckerb, A. Völpc. Phytomedicine Volume 10, Issues 2-3, 2003, Pages 213-220 doi:10.1078/094471103321659979.
So, if you are coughing due to asthma, might be time to ask your doctor where he or she gets her information.
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This seems to be a larger study
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