COLEUS

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Parts used and where grown: This attractive, perennial member of the mint (Lamiaceae) family originated in the lower elevations of India. It is now grown around the world as an ornamental plant. The root is used medicinally.

Coleus has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating	Health Concerns
	Asthma (forskolin) Glaucoma (forskolin)
	Cardiomyopathy (forskolin) Congestive heart failure Hypertension (forskolin) Obesity Psoriasis
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies): As recorded in ancient Sanskrit texts, coleus was used in Ayurvedic medicine¹ to treat heart and lung diseases, intestinal spasms, insomnia, and convulsions.

Active constituents: Forskolin, a chemical found in coleus, activates the enzyme adenylate cyclase.² This enzyme is a turnkey compound that initiates a cascade of critical events within every cell of the body. Adenylate cyclase and the chemicals it activates comprise a “second messenger” system that is responsible for carrying out the complex and powerful effects of hormones in the body. Stimulation of the second messenger system by forskolin leads to blood vessel dilation,³ inhibition of allergic reactions,⁴ and an increase in thyroid hormone secretion.⁵ Forskolin has other properties as well, including inhibition of the pro-inflammatory substance known as platelet-activating factor (PAF)⁶ and inhibition of the spread of cancer cells.⁷

Studies in healthy humans, including at least one double-blind trial, have shown that direct application of an ophthalmic preparation of forskolin to the eyes lowers eye pressure,^{8 9} thus reducing the risk of glaucoma. Direct application of the whole herb to the eyes has not been studied and is not recommended.

Forskolin may help dilate blood vessels and improve the forcefulness with which the heart pumps blood. A preliminary trial found that forskolin reduced blood pressure and improved heart function in people with cardiomyopathy.¹⁰ It is unknown if oral coleus extracts would have the same effect. A small double-blind trial found that inhaled forskolin could decrease lung spasms in asthmatics.¹¹ It is unclear if oral ingestion of coleus extracts will provide similar benefits.

How much is usually taken? Coleus extracts standardized to 10 to 18% forskolin are available. While some doctors expert in herbal medicine recommend 50–100 mg two to three times per day of standardized coleus extract, these amounts are extrapolations and have yet to be confirmed by direct clinical research.¹² Most studies have used injected forskolin, so it is unclear if oral ingestion of coleus extracts will provide similar benefits in the amounts recommended above. Until ophthalmic preparations of coleus or forskolin are available, people with glaucoma should consult with a skilled healthcare practitioner to obtain a sterile fluid extract for use in the eyes.

Are there any side effects or interactions? Few adverse effects of coleus have been reported. It should be avoided in people with ulcers, because it may increase stomach acid levels. Direct application to the eyes may cause transitory tearing, burning, and itching. The safety of coleus in pregnancy and breast-feeding is unknown.

Are there any drug interactions? Certain medications may interact with coleus. Refer to the drug interactions safety check for a list of those medications.

1. Dubey MP, Srimal RC, Nityanand S, Dhawan BN. Pharmacological studies on coleonol, a hypotensive diterpene from Coleus forskohlii. J Ethnopharmacol 1981;3:1–13.

2. Seamon KB, Daly JW. Forskolin: A unique diterpene activator of cAMP-generating systems. J Cyclic Nucleotide Res 1981;7:201–24 [review].

3. Wysham DG, Brotherton AF, Heistad DD. Effects of forskolin on cerebral blood flow: Implications for the role of adenylate cyclase. Stroke 1986;17:1299–303.

4. Marone G, Columbo M, Triggiani M, et al. Forskolin inhibits the release of histamine from human basophils and mast cells. Agents Actions 1986;18:96–9.

5. Roger PP, Servais P, Dumont JE. Regulation of dog thyroid epithelial cell cycle by forskolin, an adenylate cyclase activator. Exp Cell Res 1990;172:282–92.

6. Wong S, Mok W, Phaneuf S, et al. Forskolin inhibits platelet-activating factor binding to platelet receptors independently of adenylyl cyclase activation. Eur J Pharmacol 1993;245:55–61.

7. Agarwal KC, Parks RE. Forskolin: A potential antimetastatic agent. Int J Cancer 1983;32:801–4.

8. Caprioli J, Sears M. Forskolin lowers intraocular pressure in rabbits, monkeys and man. Lancet 1983;1:958–60.

9. Badian M, Dabrowski J, Grigoleit HG, et al. Effect of forskolin eye drops on intraocular pressure in healthy males. Klin Monatsbl Augenheilkd 1984;185:522–6 [in German].

10. Kramer W, Thormann J, Kindler M, Schlepper M. Effects of forskolin on left ventricular function in dilated cardiomyopathy. Arzneim Forsch 1987;37:364–7.

11. 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;43:76–83.

12. Bone K, Morgan M. Clinical Applications of Ayurvedic and Chinese Herbs: Monographs for the Western Herbal Practitioner. Queensland, Australia: Phytotherapy Press, 1996.

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