This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Polygala Senega. Universally official. Bitter Polygala, P. amara, is official in Denmark. This latter plant grows in the United States and, like the many native species of Polygalaceae, is a bitter tonic. Milkworts in general should be given more detailed study than they have received.
The studies of Henderson and Taylor showed that senega causes a good flow of bronchial secretion and acts reflexly, somewhat similarly to ipecac, antimony, and the ammonium compounds, except it must be noted that emetine, derived from ipecac, has both a reflex and a central action.
Senega is an irritant to all mucous membranes and is classed as a stimulating expectorant.
Injected into the circulation senega disintegrates the red corpuscles and stops the heart in diastole; there are convulsions, followed by paralysis of the respiratory center. Its irritating properties might be dangerous were much of it absorbed; but little is absorbed. Senega, in considerable dosage, is diuretic, emetic, cathartic, and emmenagogue; but it is too irritating to use in any but very moderate doses.
Senega has a narrow but very useful range of employment, that of a most efficient stimulating expectorant; it should never be used in acute affections. But where the secretion of mucus is deficient in subacute and chronic bronchitis, and it is necessary to promote expectoration, senega is one of the drugs of choice. It should not be administered if gastro-enteric irritability exists. Senega is commonly prescribed in combination with other expectorants.
The average dose of the fl. is 15 minims, of the syrup 1 fluidrachm.