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The main cough medicine I use (I am in Australia) contains Pentoxyverine as an active ingredient. The wikipedia article for this chemical states the outcome of reducing a cough, but curiously states no understood mechanism for this outcome:

Pentoxyverine suppresses the cough reflex in the central nervous system, but the exact mechanism of action is not known with certainty.

Wikipedia also says no clinical trials are available.

My initial research into cough medicines has turned up a whole host of skeptic websites claiming that studies show cough mixtures are ineffective at stopping a cough.

I understand that some medicines have been proven to work even though we do not understand their mechanism. But in this case the lack of an understood mechanism adds to my overall skepticism.

Does anyone know of any studies that assert whether this ingredient is effective or not?

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Define work(ie what symptoms is it supposed to treat) and find a claim that the cough syrups do treat that (those) symptom(s) and I will up vote. But as the question stands I think it is to vague to reasonably answer. Your problem may lie in unreasonable expectations. –  Chad Mar 15 '12 at 13:09
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@ratchetfreak I understand that honey is antiseptic and antibacterial. –  ChrisW Mar 17 '12 at 1:44
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This is too broad to have an answer really. It's like asking: "Do pain-killers work? I've tried aspirin and was not very effective...". Please restrict the question to one kind of cough suppressant molecule (e.g. "Pentoxyverine"). Thanks. –  Sklivvz Mar 17 '12 at 10:43
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The fact that a product's mechanism of action is not know does not make it inefficacious. For instance, lithium salts have been used for the treatment of bipolar disorders for decades, and still their mechanism of action is unknown. –  nico Mar 17 '12 at 14:09
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@Oddthinking Honey wouldn't be the first thing I'd think of if I had a wound to manage (I'm not a doctor): just saying there may be more to honey than only texture. –  ChrisW Mar 17 '12 at 16:44

1 Answer 1

up vote 3 down vote accepted

TL/DR: There are no quality studies supporting the Pentoxyverine. The class of drugs that Pentoxyverine belongs to does not have strong support either.


Our good friends at the Cochrane Collaboration, who do high-quality meta-analyses, looked at over-the-counter cough medicines:

(Ambulatory settings roughly means medical care not in a hospital ward.)

They looked at twenty-five trials involving 3492 people (separating adults and children), and they looked at expectorants, antihistamines, antihistamine decongestants, antitussives, bronchodilators and guaifenesin.

Their conclusion:

The evidence for effectiveness of oral over-the-counter cough medicines is weak

Acute cough is a common and troublesome symptom in people who suffer from acute upper respiratory tract infection (URTI). Many people self-prescribe over-the-counter (OTC) cough preparations and health practitioners often recommend their use for the initial treatment of cough. The results of this review suggest that there is no good evidence for or against the effectiveness of OTC medications in acute cough. The results of this review have to be interpreted with caution because the number of studies in each category of cough preparations was small. Many studies were of low quality and very different from each other, making evaluation of overall efficacy difficult.

Now, there were no trials included that covered Pentoxyverine. However, Pentoxyverine is an antitussive, and there were a total of 8 trials that covered antitussives. So the class of drugs was tested, and did not provide clear evidence for or against, but the individual drug wasn't covered.

Further, looking at their selection criteria, any high-quality studies of Pentoxyverine should have been found and included. We can conclude that a careful search by these researchers for quality trials of Pentoxyverine found none.

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That's great to know! Especially when almost everyone I raise this issue with seems SO SURE that cough medicines help their cough. I'll be sure to push the point the next time a doctor tries to tell me to spend my money on a cough syrup... –  Brian Hinchey Jun 19 '13 at 1:29
    
While having a similar discussion with a friend on Facebook, I unearthed this 1977 trial comparing two different drug combinations, and finding one was better than the other: I am not sure why it didn't meet Cochrane's standards. (Or perhaps it did, but was countered by other studies.) –  Oddthinking Jun 19 '13 at 1:34

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