Feverfew: Uses. Dosage
PROPHYLAXIS OF MIGRAINE HEADACHE
The first double-blind study investigating feverfew in migraine prophylaxis was published in 1985 and involved 17 patients who had been chewing fresh feverfew leaves on a daily basis. Therapeutic effect was maintained when capsules containing freeze-dried feverfew powder were continued, whereas those allocated placebo capsules experienced a significant increase in the frequency and severity of headache, nausea, and vomiting during the early months of withdrawal.
Since then, numerous clinical studies have been conducted to determine the role of feverfew in the prevention of migraine headache.
In 2000, Ernst and Pittler published a systematic review of six randomised, placebo-controlled double-blind trials of feverfew as a prophylactic treatment and concluded that the current evidence favours feverfew as an effective preventative treatment against migraine headache, and is generally well tolerated.
Clinical note — Migraine
Migraine is a common episodic familial headache disorder characterised by a combination of headache and neurologic, gastrointestinal, and autonomic symptoms. It has a 1 -year prevalence of approximately 18 % in women, 6% in men, and 4% in children before puberty. Several underlying mechanisms are considered responsible for the onset of migraine.
One of the genes linked to migraine is associated with dysfunction in P-type neuronal calcium channels, which mediate 5-HT and excitatory neurotransmitter release. This dysfunction can impair release of 5-HT and predispose patients to migraine attacks or impair their self-aborting mechanism. Additionally, NO may be involved in the initiation and maintenance of migraine headache. Migraine aura is now thought to be caused by neuronal dysfunction, not ischaemia, and headache begins while cortical blood flow is reduced.
In clinical practice, the three goals of migraine-preventive therapy are to reduce attack frequency, severity, and duration, improve responsiveness to treatment of acute attacks, and improve function and reduce disability. Ultimately, choice of treatment should be based on efficacy, adverse effects and coexistent conditions with a full therapeutic trial taking 2-6 months.
A more recent Cochrane systematic review of five placebo-controlled, randomised, double-blind trials (n = 343) concluded that there was insufficient evidence to determine whether feverfew was superior to placebo in reducing migraine frequency or incidence, severity of nausea or severity of migraines. A closer look at the studies reveals that results were mixed, methodological quality varied and various dosage regimens, administration forms and extracts were used. One study used three different dosing regimens for a C02 extract, two studies used an alcoholic and C02 extract, three studies used dried feverfew leaves for 8-24 weeks and one study used an alcoholic extract for 8 weeks. Interpretation of test results is made even more difficult when one considers the naturally occurring chemical variations among the preparations.
The authors have offered several explanations for the inconsistent clinical findings and point out that previous negative studies used extracts standardised for parthenolide concentration; however, it is possible that other compounds found in whole-leaf preparations may also be important for pharmacological activity. In vivo studies support this view. Additionally, the negative results obtained by some studies may be due to under-dosing.
Since then, positive results were obtained for a C02-extract of feverfew in a randomised, double-blind, placebo-controlled, multicentre study of 170 patients. Active treatment with feverfew (MIG-99) at a dose of 6.25 mg, three times daily, significantly reduced the frequency of migraine headache episodes over a 16-week period.
Although traditionally used as a treatment for inflammatory joint conditions, the results of a randomised, double-blind study involving 41 patients with symptoms of RA found no difference between chopped dried feverfew (70-86 mg) or placebo after 6 weeks’ treatment.
Parthenolide-free feverfew extract is being investigated in various dermatological conditions. One study found that the formulation protected skin against inflammation and UV-induced damage. When the pathenolide-free feverfew extract was topically applied, it significantly reduced the loss of cell viability, the increase in proinflammatory mediator release and the induction of DNA damage induced by solar simulated UV radiation in a human epidermal model. It also exhibited potent antioxidant activity in vitro. Other in vitro tests have revealed that parthenolide-free feverfew extract reduces inflammation through several mechanisms and is being investigated further as a novel non-steroidal extract for irritated skin.
In vitro tests suggest that parthenolide may have potential as a radiation sensitiser. According to the study, parthenolide inhibits NF-kappa-B activity, slows cell growth, and synergistically enhances cell killing after moderate doses of radiation.
Feverfew has been used traditionally to treat coughs and colds, fevers, atonic dyspepsia, worm infestation, menstrual disorders, nervous debility, joint pain and headaches.
• Dried leaf: 50 mg to 200 mg daily
• Fresh plant tincture (1:1): 0.7-2.0 miyday.
• Dried plant tincture (1:5): 1-3 miyday.
• Prevention of migraine headaches (based on clinical studies): 125-250 mg/day of powder, standardised to contain a minimum parthenolide content of 0.2%, or 400 µg, which should betaken for at least 4 months. It is still controversial as to whether standardised extracts are best for migraine prophylaxis or not.