Bladder-wrack, Fucus vesiculosus, Linn. (Order Fucaceae), is one of the commonest seaweeds on the coast of Great Britain. For medicinal use the plant should be freshly gathered from the rocks, on which it grows, and dried. The drug consists of the dried, nearly black, thin, flattened branching thallus, about 18 millimetres wide, and sometimes as much as a metre in length. When quite dry it is hard and brittle, but becomes softer and cartilaginous when moist. It has an entire margin, and bears air vesicles in pairs. Some of the branches terminate in thickened enlargements, in which the reproductive organs are situated. The drug has a seaweed-like odour and a disagreeable, mawkish taste. Fucus serratus, Linn., is also commonly found on the sea-shore, but may be distinguished from F. vesiculosus by its serrated margin and absence of air vesicles. Fucus nodosus, Linn., which is also common, has single vesicles.
Constituents.—The chief constituent of bladder-wrack is a gelatinous substance, algin, but the drug also contains marmite. It yields about 1.6 to 3 per cent. of ash, and contains about 0.01 per cent. of iodine, which is said to exist in the seaweed in the form of an organic compound, similar to that found in the thyroid gland.
Action and Uses.—Bladder-wrack has been used to reduce glandular swellings, but is now employed principally as an "antifat," forming the basis of most advertised nostrums of this nature. It has been stated to influence the activity of the thyroid gland to a greater extent than any other iodine compound for the proportion of iodine present. For the preparation of pills the solid Extractum Fuci is suitable. The liquid extract is used in mixture form, generally with alkali iodides, and sometimes in combination with Liquor Thyroidei, another remedy which increases metabolism and hence diminishes weight. The alginic acid obtained from seaweed is used to form an organic compound with iron, which is sold under the trade-name Algiron, or Alginoid Iron. It contains about 11 per cent. of iron, and is given in doses of 2 to 10 decigrams (3 to 15 grains).
- Extractum Fuci, B.P.C.—EXTRACT OF BLADDER-WRACK.
- Given in pills, massed with powdered liquorice or marsh-mallow root, to reduce glandular swellings, and in obesity. Dose.—2 to 6 decigrams (3 to 10 grains).
- Extractum Fuci Liquidum, B.P.C.—LIQUID EXTRACT OF BLADDER-WRACK. 1 in 1.
- This preparation is the basis of many nostrums advertised to cure obesity. Sodium and potassium iodides are often added to supplement the small proportion of iodine present. Dose.—4 to 8 mils (1 to 2 fluid drachms).