Motherwort contains a chemical called leonurine, which is a uterine stimulant. A warm cup of motherwort tea can bring on suppressed menstruation in women.

Primary functions:
Motherwort is an excellent heart tonic.
Can reduce the hot flashes of menopause.
Has sedative qualities.
Promotes menstruation.

Other benefits:
Motherwort can relieve heart conditions such as palpitations and tachycardia.
Eases all sorts of nervous tension.
May be an effective treatment for insomnia.
Used to relieve the symptoms of menopause and PMS.
May be taken during painful menstrual periods, especially those associated with anxiety.

Medicinal Action and Uses
Diaphoretic, antispasmodic, tonic, nervine, emmenagogue. Motherwort is especially valuable in female weakness and disorders (hence the name), allaying nervous irritability and inducing quiet and passivity of the whole nervous system.

As a tonic, it acts without producing febrile excitement, and in fevers, attended with nervousness and delirium, it is extremely useful.

Old writers tell us that there is no better herb for strengthening and gladdening the heart, and that it is good against hysterical complaints, and especially for palpitations of the heart when they arise from hysteric causes, and that when made into a syrup, it will allay inward tremors, faintings, etc. There is no doubt it has proved the truth of their claims in its use as a simple tonic, not only in heart disease, neuralgia and other affections of the heart, but also in spinal disease and in recovery from fevers where other tonics are inadmissable.

In Macer's Herbal we find 'Motherwort' mentioned as one of the herbs which were considered all-powerful against 'wykked sperytis.'

The best way of giving it is in the form of a conserve, made from the young tops, says one writer. It may be given in decoctions, or a strong infusion, but is very unpleasant to take that way. The infusion is made from 1 oz of herb to a pint of boiling water, taken in wineglassful doses*.

Culpepper wrote of Motherwort:
'Venus owns this herb and it is under Leo. There is no better herb to drive melancholy vapours from the heart, to strengthen it and make the mind cheerful, blithe and merry. May be kept in a syrup, or conserve, therefore the Latins call it cardiaca.... It cleansethe the chest of cold phlegm, oppressing it and killeth worms in the belly. It is of good use to warm and dry up the cold humours, to digest and disperse them that are settled in the veins, joints and sinews of the body and to help cramps and convulsions.'
And Gerard says:
'Divers commend it against infirmities of the heart. Moreover the same is commended for green wounds; it is also a remedy against certain diseases in cattell, as the cough and murreine, and for that cause divers husbandmen oftentimes much desire it.'

 Not to be used during pregnancy. Those with clotting disorders or high blood pressure should use this herb with caution.

• Dosage
  Extract: Mix 10 to 15 drops in warm water up to three times daily.
  Infusion: Up to 2 cups daily.
  Tincture: One-half to 1 teaspoon up to twice daily.

References

• Complete Medicinal Herbal by Penelope Ody.

• The Healing Herbs : The Ultimate Guide To The Curative Power Of Nature's Medicines by Michael Castleman.

• Herbal Delights by C.F. LEYEL.

• The Herbal Menopause Book by Amanda McQuade Crawford.

• Illustrated Herb Encyclopedia by Kathi Keville.

• The Master Book of Herbalism by Paul Beyerl.

• The Bootstrap Guide to Medicinal Herbs in the Garden, Field & Marketplace (Bootstrap Guide) by Lee Sturdivant, Tim Blakley.

• Planetary Herbology by Dr. Michael Tierra.

• The Roots of Healing: A Woman's Book of Herbs by Deb Soule, Susan Szwed.

• A Modern Herbal by M Grieve.