Monograph: |
Linoleic Acid
Adverse Effects and Precautions
Evening primrose oil, and presumably other sources of gamo-
lenic and linoleic acids, can produce minor gastro-intestinal
disturbances and headache. It can precipitate symptoms of
undiagnosed temporal lobe epilepsy and should be used with
caution in patients with a history of epilepsy or those taking
epileptogenic drugs, in particular phenothiazines. Hypersen-
sitivity reactions may also occur.
Effects on the nervous system. Temporal lobe epilepsy
was diagnosed following treatment with evening primrose oil
in 3 patients who had previously been diagnosed as schizo-
phrenic. Grand mal seizures occurred in 2 additional schizo-
phrenic patients during treatment with evening primrose oil.
All of these patients had received or were taking phenothi-
azine neuroleptics.
Uses and Administration
Linoleic and gamolenic acid are essential fatty acids of the
omega-6 series which act as prostaglandin precursors: endog-
enous gamolenic acid is derived from linoleic acid which is
an essential constituent of the diet. Evening primrose oil,
which contains these acids, is used for symptomatic relief of
atopic eczema and mastalgia. Typical doses expressed as
gamolenic acid are 320 to 480 mg daily in divided doses in
eczema, and 240 to 320 mg daily in divided doses for mastal-
gia. Evening primrose oil has been investigated in a variety of
other disorders including multiple sclerosis, diabetic neurop-
athy, rheumatoid arthritis, chronic fatigue syndrome, and the
premenstrual syndrome, as indicated by the cross references
given below. Mixtures of essential fatty acids (including EF-
4, EF-12. and EF-27) derived from evening primrose oil and
other oils have also been investigated in various conditions.
including diabetic neuropathy, restenosis following angi-
opiasty and skin damage following radiotherapy.
Other plant oils which have been used similarly to evening
primrose oil as sources of gamolenic acid include blackcur-
rant seed oil and borage oil (star flower oil ). Products
containing gamolenic acid-rich plant oils are promoted in many
countries as dietary supplements, often in combination with
fish oils or other sources of omega-3 triglycerides.
Eczema. Atopic eczema may be due to a defect in
essential fatty acid metabolism and some beneficial sympto-
matic effects have been reported with evening primrose oil. 12
Meta-analysis of 9 studies involving 311 patients has report-
ed improvement in disease symptoms, especially itching, but
a more recent study in 123 patients found no therapeutic ef-
fect of evening primrose oil, aJone or with fish oil. Although
the design and interpretation of this study has been criticised
by the manufacturers of evening primrose oil the authors
consider such criticism invalid, and point out that an earlier
large study yielded similar results' No difference was found
between placebo and evening primrose oil in a further study
in children with eczema, and there was also no effect on asth-
ma symptoms in those patients suffering from both disorders.
Benefit has been reported in infants with seborrhoeic derma-
titis from local application of borage oil.
Mastalgia. Gamolenic acid (usually given in the form of
evening primrose oil) has fewer adverse effects than drugs
such as danazol or bromocriptine and some authorities prefer
it for mastalgia , especially in patients with less se-
vere symptoms or those who require prolonged or repeated
treatment.
Menopausal disorders. For reference to a study suggesting
that evening primrose oil is of no benefit in preventing meno-
pausal vasomotor symptoms, see under Benefits and Risks of
HRT.
Multiple sclerosis. There is some evidence that modifying
the intake of diatary fats and supplementing the diet with
omega-6 polyunsaturated fatty acids, such as linoleic acid,
could influence the clinical course of multiple sclerosis
and many patients practice dietary modification, including taking
evening primrose oil. Some studies have shown a reduction in
severity and duration of relapse in patients taking linoleic
acid supplements (as sunflower oil) and
another has reported benefit in patients who limited their in-
take of dietary saturated fatty acids and supplemented their
diet with polyunsaturated fatty acids. However, the relation-
ship between dietary fat and multiple sclerosis cannot be
considered proven.
Premenstrual syndrome. Progressive improvement in
premenstrual syndrome was reported over 5 cycles in an open
pilot study in 19 patients receiving evening primrose only.
However, subsequent results have not demonstrated any ben-
efit. Evening primrose oil may be considered for cyclical
mastalgia associated with premenstrual syndrome, but other
drugs are preferred if other symptoms predominate.
Rheumatoid arthritis. In a study by Belch et at. patients
with rheumatoid arthritis taking NSAIDs showed sub-
jective improvement following 12 months treatment with
evening primrose oil with or without fish oil, compared with
placebo. A clinically important reduction in signs and symp-
toms of disease activity has also been seen in patients
treated with gamolenic acid in the form of borage oi1. Jantli et
al.have demonstrated that during treatment with evening prim-
rose oil patients with rheumatoid arthritis have an increased
plasma concentration of gamolenic, dihomo-gamma-lino-
lenic, and arachidonic acids and a decreased plasma concen-
tration of oleic and eicosapentaenoic acids and apolipoprotein.
The increase in plasma-arachidonic acid and decrease in
eicosapentaenoic acid may be unfavourable in patients with
rheumatoid arthritis since arachidonic acid is the precursor of
inflammatory prostaglandins and eicosapentaenoic acid may
have an anti-inflammatory role.
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