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 the 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 B, Eberhardt R, Stammer H:
Study objective: To assess the efficacy and tolerability of a fixed fluid extract combination of thyme and ivy leaves (thyme-ivy combination) and matched placebo in patients suffering from acute bronchitis with productive cough.
Results: The mean reduction in coughing fits on days 7 to 9 relative to baseline was 68.7 % under thyme-ivy combination compared to 47.6 % under placebo (p < 0.0001). In the thyme-ivy combination group, a 50 % reduction in coughing fits from baseline was reached 2 days earlier compared to the placebo group. The symptoms of acute bronchitis (BSS) improved rapidly in both groups, but regression of symptoms was faster and the responder rates (p < 0.0001) compared to placebo were higher at Visit 2 (83.0 % vs 53.9 %) and Visit 3 (96.2 % vs 74.7 %) under the treatment of thyme-ivy combination. Treatment was well tolerated with no difference in the frequency or severity of AEs between thyme-ivy combination and placebo groups. Severe or serious AEs were not reported.
Conclusion: Oral treatment of acute bronchitis with thyme-ivy combination for about 11 days was superior to placebo in terms of efficacy. The treatment was safe and well tolerated.
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!):
Although many studies conclude that ivy extracts are effective to reduce symptoms of acute URTIs, their effectiveness is not established beyond reasonable doubt. The studies reviewed show serious methodological flaws and lack placebo controls. Therefore their findings must be interpreted with due caution. For a combination of ivy and thyme, effectiveness has been demonstrated in one RCT, however these findings need to be confirmed.
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
RESULTS: Seventeen randomised clinical trials were found, six of which concerned the use of traditional Chinese herbal medicine and eight described traditional Indian medicine, of which five investigated Tylophora indica. Three other randomised trials tested a Japanese Kampo medicine, marihuana, and dried ivy leaf extract. Nine of the 17 trials reported a clinically relevant improvement in lung function and/or symptom scores.
CONCLUSIONS: No definitive evidence for any of the herbal preparations emerged. Considering the popularity of herbal medicine with asthma patients, there is urgent need for stringently designed clinically relevant randomised clinical trials for herbal preparations in the treatment of asthma.
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.
The trials included in this review indicate that ivy leaf extract preparations have effects with respect to an improvement of respiratory functions of children with chronic bronchial asthma, but more far-reaching conclusions can hardly be drawn because of a meagre database, including the fact that only one primary trial included a placebo control. Further research, particularly into the long-term efficacy of the herbal extract, is needed.
So, if you are coughing due to asthma, might be time to ask your doctor where he or she gets her information.
Preparations of ivy leaves dry extract are used in the treatment of upper respiratory tract conditions characterized by hypersecretion of a viscous mucus and coughing. The extracts are well tolerated by children and adults suffering from acute or chronic obstructive bronchitis and the efﬁcacy of a special extract (EA 575,DER 5-7.5:1, 30% m/m EtOH) has been conﬁrmed by placebo controlled clinical trials and post-marketing surveillance studies.