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A member of the mint family, Coleus forskohlii grows wild on the mountain slopes of Nepal, India, and Thailand. In traditional Asian systems of medicine, it was used for a variety of purposes, including treating skin rashes, asthma, bronchitis, insomnia, epilepsy, and angina. But modern interest is based almost entirely on the work of a drug company, Hoechst Pharmaceuticals.
Like other drug manufacturers, Hoechst regularly screens medicinal plants in hopes of discovering new medications. In 1974, work performed in collaboration with the Indian Central Drug Research Institute found that the rootstock of Coleus forskohlii could lower blood pressure and decrease muscle spasms. Intensive study identified a substance named forskolin that appeared to be responsible for much of this effect.
Like certain drugs used for asthma, forskolin increases the levels of a fundamental natural compound known as cyclic AMP.1,2 Cyclic AMP plays a major role in many cellular functions, and some drugs that affect it relax the muscles around the bronchial tubes.
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What Is Coleus forskohlii Used for Today?
Herb manufacturers have begun to offer extracts of Coleus forskohlii that have been specially manufactured to contain high levels of forskolin.
Forskolin has been found to stabilize the cells that release histamine and other inflammatory compounds.3 This suggests that Coleus forskohlii may be a useful treatment for asthma, eczema, and other allergic conditions.
Studies have also found that forskolin relaxes smooth muscle tissue.4,5 For this reason, Coleus forskohlii has been suggested as a treatment for asthma, menstrual cramps or dysmenorrhea, angina, irritable bowel syndrome (spastic colon), crampy bladder pain (as in bladder infections), and hypertension (high blood pressure).
Coleus forskohlii has also been proposed as a treatment for psoriasis, because that disease appears to be at least partly related to low levels of cyclic AMP in skin cells.
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What Is the Scientific Evidence for Coleus forskohlii?
The scientific evidence for the herb Coleus forskohlii as a treatment for any disease is weak. What is known relates to the substance forskolin rather than the whole herb.
Animal studies and open studies in humans suggest that forskolin can reduce blood pressure and dilate bronchial tubes.6 –9 A tiny double-blind study indicates that forskolin taken by inhalation may be as effective as standard asthma inhalers,10 and forskolin eyedrops appear to improve glaucoma.11
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Dosage
A common dosage recommendation is 50 mg 2 or 3 times a day of an extract standardized to contain 18% forskolin.
However, because such an extract provides significant levels of forskolin, a drug with wide-ranging properties, we recommend that Coleus forskohlii extracts be taken only with a doctor's supervision.
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Safety Issues
The safety of Coleus forskohlii and forskolin has not been fully evaluated, although few significant risks have been noted in studies performed thus far. Caution should be exercised when combining this herb with blood-pressure medications and "blood thinners." Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established.
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Interactions You Should Know About
If you are taking blood pressure medications such as beta-blockers, clonidine, or hydralazine, or blood-thinning drugs such as Coumadin (warfarin), heparin,Plavix (clopidogrel), Ticlid (ticlopidine), or Trental (pentoxifylline),Coleus forskohlii should only be used under the supervision of a physician.
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References
1. Seamon KB, Daly JW. Forskolin: a unique diterpene activator of cAMP-generating systems. J Cyclic Nucleotide Res. 1981;7:201–224.
2. Laurenza A, Sutkowski EM, Seamon KB. Forskolin: a specific stimulator of adenylyl cyclase or a diterpene with multiple sites of action? Trends Pharmacol Sci. 1989;10:442–447.
3. Marone G, Columbo M, Triggiani S, et al. Forskolin inhibits the release of histamine from human basophils and mast cells. Agents Actions. 1986;18:96–99.
4. Ammon HPT, Muller AB. Forskolin: from an Ayurvedic remedy to a modern agent. Planta Med. 1985:473–477.
5. DeSouza NJ. Industrial development of traditional drugs: the forskolin example. A mini-review. J Ethnopharmacol. 1993;38:177–180.
6. Kreutner W, Chapman RW, Gulbenkian A, et al. Bronchodilatory and antiallergy activity of forskolin. Eur J Pharmacol. 1985;111:1–8.
7. Schlepper M, Thormann J, Mitrovic V. Cardiovascular effects of forskolin and phosphodiesterase-III inhibitors. Basic Res Cardiol. 1989;84(suppl 1):197–212.
8. Dubey MP, Srimal RC, Nityanand S, et al. Pharmacological studies on coleonol, a hypotensive diterpene from Coleus forskohlii. J Ethnopharmacol. 1981;3:1–13.
9. Yousif MH, Thulesius O. Forskolin reverses tachyphylaxis to the bronchodilator effects of salbutamol: an in-vitro study on isolated guinea-pig trachea. J Pharm Pharmacol. 1999;51:181–186.
10. Bauer K, Dietersdorfer F, Sertl K, et al. Pharmacodynamic effects of inhaled dry powder formulations of fenoterol and colforsin in asthma. Clin Pharmacol Ther. 1993;53:76–83.
11. Meyer BH, Stulting AA, Muller FO, et al. The effects of forskolin eye drops on intraocular pressure. S Afr Med J. 1987;71:570–571.
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