Expert opinions on whether dextromethorphan
effectively suppresses cough are all over the
map.
During an FDA advisory panel meeting,
Priscilla Callahan-Lyon of FDA's Division of
Nonprescription Clinical Evaluation noted research
supports a modest effect on cough for DXM (see
preceding story).
But she also pointed to a 2009 Cochran Review
of OTC medications for acute cough in children and
adults in an ambulatory setting that called into
question DXM's efficacy. According to the study, which
included 25 trials, "there is no good evidence for or
against the effectiveness of OTC medicine in an acute
cough."
Three of the 25 trials included DXM. One
randomized, placebo-controlled study of 43 patients
found no statistical difference between DXM and a
placebo. Another found DXM decreased coughs 19 percent
to 36 percent, but was not consistently statistically
different from a placebo throughout the dosing
interval.
The third study was a meta-analysis of six DXM
studies that found the drug statistically significantly
lowered cough bouts, effort and latency an average of
12 percent to 17 percent. However, none of the
individual studies showed statistically significant
differences, Callahan-Lyon said.
She noted these studies served as a partial
foundation for the American College of Chest
Physicians' weak recommendation for DXM to treat
chronic cough due to acute bronchitis, recommendation
not to use DXM to treat cough from upper respiratory
infections and moderate recommendations to use DXM for
coughs due to chronic bronchitis and bacterial
sinusitis or early pertussis infection.
The American Academy of Pediatrics say the
"cumulative evidence" shows DXM does not relieve
children's cough and cold symptoms better than a
placebo, and argued in comments submitted to the
advisory committee prior to the Sept. 14 meeting that
the risk of DXM abuse is greater than the benefits
("The
Tan Sheet" Sept. 13, 2010, In
Brief).
However, not everyone thinks the glass is half
empty.
The "absence of evidence is not evidence of
the absence of effect," Peter Dicpinigaitis, professor
of clinical medicine at the Albert Einstein College of
Medicine, argued at the meeting. He presented at the
meeting on behalf of the Consumer Healthcare Products
Assocation.
He said he often recommends DXM for cough
relief and has observed its efficacy in patient
anecdotes.
Indeed, Callahan-Lyon noted studies that
justified adding DXM to the monograph showed a 10 mg
dose of DXM reduced the number of coughs 26.3 percent,
84 percent of patients experienced "moderate to marked
improvement in cough" and that DXM is less sedating
than codeine.
- Elizabeth Crawford ([email protected])
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