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- Peppermint (Mentha × piperita, Lamiaceae)
- Irritable Bowel Syndrome
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Date:
01-13-2017 | HC# 031641-560
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Re: Clinical Trials Indicate Peppermint Oil May Provide Benefit for Irritable Bowel Syndrome
Haber
SL, El-Ibiary SY. Peppermint oil for treatment of irritable bowel syndrome. Am J Health Syst Pharm. January
2016;73(2):22, 24, 26, 28, 30-31.
Irritable
bowel syndrome (IBS), a chronic gastrointestinal (GI) disorder, affects 5-15%
of the world's population, reducing their quality of life. A lack of
efficacious and acceptable medical treatments impels 20-50% of those with IBS
to seek complementary therapies, including natural products.
Peppermint
(Mentha × piperita, Lamiaceae) oil is historically used to treat GI
complaints. Peppermint oil, which is obtained by steam distillation of the whole
flowering herb, contains compounds including menthol, menthone, menthyl
acetate, isomenthone, 1,8-cineole, limonene, β-myrcene, and carvone. Peppermint
is an antispasmodic that has been shown to cause relaxation of intestinal
muscle and the lower esophageal sphincter in vitro and in vivo. It is suggested
to block calcium channels that affect smooth muscle. Reported antiemetic
effects may be due in part to interactions with histamine, serotonin, and
cholinergic receptors in the GI tract. Peppermint oil may have free radical scavenging
activities that can help prevent GI ulcers. It may also inhibit enterocyte
glucose uptake, increase bile solubility, reduce gallbladder contraction, and increase
small intestine transit time.
Nine
English-language, controlled, clinical studies of peppermint oil use in IBS
were located through a database search. Two were not randomized controlled trials
(RCTs) and were not reviewed for this article. Populations in the seven
included RCTs were mostly female, consistent with IBS's greater prevalence in
women. In general, most studies reported some improvement in IBS symptoms with
use of peppermint oil compared to placebo and, in one case, a conventional
pharmaceutical treatment (1-hyoscyamine, which caused adverse effects in most patients).
Adherence
was poor in some trials, with some patients withdrawing due to adverse effects
associated with peppermint oil, particularly perianal burning, heartburn,
nausea, and vomiting. Heartburn seems to be largely avoidable by the use of
enteric-coated capsules. However, enteric-coated peppermint products should not
be used by patients with achlorhydria and may increase likelihood of anal
burning in patients with diarrhea and high intestinal motility.
The
review notes several actual or hypothetical weaknesses in this body of
research. All seven RCTs were eight or fewer weeks in duration and included
relatively small numbers of patients. The authors note that none of the RCTs were
conducted in North America, and suggest that because diet and stress contribute
to IBS, results of studies may not be generalizable to patients in countries
outside the study area. They further say that content of the preparations used
is "indeterminate" because "peppermint oil is typically not
regulated by medication safety agencies (including the [US] Food and Drug
Administration [FDA])." However, they do not discuss the regulation of
peppermint oil manufactured in the countries where studies were conducted
(which are not specified) nor the adequacy of the characterization of the
products used, some of which are indicated to be standardized commercial
products. The authors acknowledge that multiple RCTs were excluded from this
review because they were not published in English.
A
2012 guidance from the FDA regarding the design of clinical trials involving
IBS should be considered in designing future studies of peppermint oil. While
peppermint oil appears to be useful in some patients with IBS, especially those
with abdominal pain or discomfort, more and larger trials are needed to better
understand its effects and possible adverse effects or contraindications,
especially in long-term use.
—Mariann
Garner-Wizard
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