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Dr. Crawfurd is correct. (rapid response 22 Sep 2004). The headline conclusion published above this POEM is totally unjustified. However did such bad research interpretation pass BMJ peer review and statistical validity assessments? Why, in the USA, can reading the original paper qualify for Medscape CME credits?
For the record : -
1. As originally marketed by Parke Davis,
all Benylin cough formulations contained diphenhydramine.¹ Most UK doctors still think of Benylin as containing diphenhydramine,
NOT dextromethorphan, (although Benafed actually contained both).
2. Among twelve over-the-counter (OTC) "Benylins" listed by today's UK manufacturer, (Pfizer), three contain dextromethorphan, one contains codeine, and one contains pholcodine. Several do not contain diphenhydramine, and one actually contains the antihistamine triprolidine instead of diphenhydramine! ²
Among label headings, only "Benylin with Codeine" indicates the drug content.
The Pfizer titles do, however, recognise that cough has multiple aetiology, and give good indication to lay buyers for matching medication to cough type. UK "Benylin Expectorant" and Benafed no longer exist.
3. In the USA, OTC "Benylin" comes in two forms.
"Benylin Expectorant" (the original UK patent name) is actually dextromethorphan syrup, and does
NOT contain diphenhydramine.
"Benylin Multi-Symptom" is marketed and classed as an antihistamine (for hay-fever) and contains pseudoephedrine in addition to diphenhydramine. ³
4. UK/USA differences aside, the trial comparisons are fundamentally inexact, because : -
(a) there is no real no-treatment control group.
(b) the placebo group is not defined and could include anything.
(c) all so-called cough "placebos", sweets, syrup, sugar, menthol, eucalyptus, liquorice, chloroform water, etc., have good clinical reasons for relieving differing cough types.
(d) the cough type is not defined. Causes of cough can be obscure and diverse. Less serious ones include tracheitis, laryngitis, post-nasal drip, nausea, pharyngitis, sore ears, and nasal obstruction with differing best management.
(e) to get valid comparisons, cough suppressants need trialling against specified cough types, e.g., those of severe influenza, measles, some forms of pharyngitis, respiratory tract neoplasm, and/or the neurological cough of pertussis. Medications for comparison must include codeine, pholcodine, physeptone, and opiate preparations like Gee's Linctus, (Linctus Scillae Opiata, 1950s NF). These medicines work. A control might be plain syrup if a "no-treatment" comparison is thought unjustifiable or unenforceable.
5. The "cough-suppressant" pharmacological classifications of diphenhydramine and dextromethorphan have long been suspect in general practice.
(i)
Diphenhydramine.
Forty odd years ago, it was said that diphenhydramine was wrongly classified as a cough suppressant. Was this a wrong BP or BPC listing? I can't recall.
In practice Benylin was useless for laryngitis and/or tracheitis, and also for the non-stop reflex swallowing and consequent abdominal air distension of the concomitant dry lower-third pharyngitis.
Chemists commonly made up Benylin mixed with codeine phosphate syrup, a dodge well known to older GPs. Later, Parke Davis introduced their own "Benylin with Codeine", presumably after realising that diphenhydramine alone did not suppress cough.
(ii).
Dextromethorphan.
More recently dextromethorphan had a chance vox populi comparison with codeine!
Actifed Compound Linctus (ACL). (Wellcome)¹ used to be a popular prescription cough suppressant cold remedy for children and adults.
Fifteen or so years ago, impending tighter OTC addictive-drug regulations and the so-called "limited list" NHS prescription exclusions forced change from prescription to OTC marketing of cough remedies. The cough-suppressant content of ACL was altered from 10mg codeine phosphate to 10mg. dextromethorphan. The change immediately drew public comment that "ACL doesn't work any more" or that "OTC ACL is different from prescribed ACL".
Postscript
By reputation, Pholtex Linctus (Riker) was probably the most effective proprietary. Its spoonful contained 15mg pholcodine with phenyltoloxamine in an ion-exchange resin, enabling 8hrly dosage.¹ Relatively expensive and never a first choice for cost-conscious NHS GPs, it disappeared in the UK, (though not elsewhere), during the limited list mass demise of ethical proprietaries for cough.
Maybe a more accurate title for this POEM would be "Some cough
suppressants are ineffective in children". The authors have not tested
either codeine or pholcodine in paediatric doses,which in my experience
are more effective than dextromethorphan or diphenhydramine and without
significant side-effects despite the Caution in the British National
Formulary, which, incidentally does not list either of the tested drugs as
a cough suppressant. Raymond Crawfurd
Cough suppressants are not ineffective in children
Dr. Crawfurd is correct. (rapid response 22 Sep 2004). The headline conclusion published above this POEM is totally unjustified. However did such bad research interpretation pass BMJ peer review and statistical validity assessments? Why, in the USA, can reading the original paper qualify for Medscape CME credits?
For the record : -
1. As originally marketed by Parke Davis,
all Benylin cough formulations contained diphenhydramine.¹ Most UK doctors still think of Benylin as containing diphenhydramine,
NOT dextromethorphan, (although Benafed actually contained both).
2. Among twelve over-the-counter (OTC) "Benylins" listed by today's UK manufacturer, (Pfizer), three contain dextromethorphan, one contains codeine, and one contains pholcodine. Several do not contain diphenhydramine, and one actually contains the antihistamine triprolidine instead of diphenhydramine! ²
Among label headings, only "Benylin with Codeine" indicates the drug content.
The Pfizer titles do, however, recognise that cough has multiple aetiology, and give good indication to lay buyers for matching medication to cough type. UK "Benylin Expectorant" and Benafed no longer exist.
3. In the USA, OTC "Benylin" comes in two forms.
"Benylin Expectorant" (the original UK patent name) is actually dextromethorphan syrup, and does
NOT contain diphenhydramine.
"Benylin Multi-Symptom" is marketed and classed as an antihistamine (for hay-fever) and contains pseudoephedrine in addition to diphenhydramine. ³
4. UK/USA differences aside, the trial comparisons are fundamentally inexact, because : -
(a) there is no real no-treatment control group.
(b) the placebo group is not defined and could include anything.
(c) all so-called cough "placebos", sweets, syrup, sugar, menthol, eucalyptus, liquorice, chloroform water, etc., have good clinical reasons for relieving differing cough types.
(d) the cough type is not defined. Causes of cough can be obscure and diverse. Less serious ones include tracheitis, laryngitis, post-nasal drip, nausea, pharyngitis, sore ears, and nasal obstruction with differing best management.
(e) to get valid comparisons, cough suppressants need trialling against specified cough types, e.g., those of severe influenza, measles, some forms of pharyngitis, respiratory tract neoplasm, and/or the neurological cough of pertussis. Medications for comparison must include codeine, pholcodine, physeptone, and opiate preparations like Gee's Linctus, (Linctus Scillae Opiata, 1950s NF). These medicines work. A control might be plain syrup if a "no-treatment" comparison is thought unjustifiable or unenforceable.
5. The "cough-suppressant" pharmacological classifications of diphenhydramine and dextromethorphan have long been suspect in general practice.
(i)
Diphenhydramine.
Forty odd years ago, it was said that diphenhydramine was wrongly classified as a cough suppressant. Was this a wrong BP or BPC listing? I can't recall.
In practice Benylin was useless for laryngitis and/or tracheitis, and also for the non-stop reflex swallowing and consequent abdominal air distension of the concomitant dry lower-third pharyngitis.
Chemists commonly made up Benylin mixed with codeine phosphate syrup, a dodge well known to older GPs. Later, Parke Davis introduced their own "Benylin with Codeine", presumably after realising that diphenhydramine alone did not suppress cough.
(ii).
Dextromethorphan.
More recently dextromethorphan had a chance vox populi comparison with codeine!
Actifed Compound Linctus (ACL). (Wellcome)¹ used to be a popular prescription cough suppressant cold remedy for children and adults.
Fifteen or so years ago, impending tighter OTC addictive-drug regulations and the so-called "limited list" NHS prescription exclusions forced change from prescription to OTC marketing of cough remedies. The cough-suppressant content of ACL was altered from 10mg codeine phosphate to 10mg. dextromethorphan. The change immediately drew public comment that "ACL doesn't work any more" or that "OTC ACL is different from prescribed ACL".
Postscript
By reputation, Pholtex Linctus (Riker) was probably the most effective proprietary. Its spoonful contained 15mg pholcodine with phenyltoloxamine in an ion-exchange resin, enabling 8hrly dosage.¹ Relatively expensive and never a first choice for cost-conscious NHS GPs, it disappeared in the UK, (though not elsewhere), during the limited list mass demise of ethical proprietaries for cough.
1. APBI
Data Sheet Compendium, 1976.
2. OTC MIMS. http://www.emims.net/
3. Drug Information on Line. http://www.drugs.com
Competing interests:
None declared
Competing interests: No competing interests