Levoxyl & Herbs Side Effects

Levoxyl is the brand name for levothyroxine, a synthetic form of the thyroid hormone thyroxine that is used to treat hypothyroidism, or underactive thyroid. It is also used to treat goiter, a condition characterized by an enlarged thyroid due to cancer, radiation, surgery or hormonal imbalance. Before using this medication, make sure your physician is informed about other medicines you take, because many other drugs, including dietary supplements and herbs, can produce side effects when used at the same time.

Drug Description

Thyroxine, more commonly known as T4, is a hormone secreted by the thyroid that regulates metabolism. If your thyroid doesn’t manufacture enough T4, you may feel tired all the time, gain weight, develop dry skin and a sensitivity to cold and even experience hair loss. Levoxyl helps counter symptoms of low thyroid function by supplying a substitute for your natural thyroid hormone. In the case of goiter, Levoxyl decreases levels of thyroid-stimulating hormone, or TSH, which is responsible for thyroid enlargement.

Soy

Dietary supplements that contain soya lecithin extracted from the soy bean plant are intended to introduce isoflavones, phytochemicals that promote estrogen-like properties. However, according to the “Physicians’ Desk Reference for Herbal Medicines,” soy-based preparations impair the absorption of Levoxyl in the intestinal tract and decrease the drug's effectiveness.

Bladderwrack

In herbal medicine, this seaweed is used to treat low adrenal function and thyroid disorders. Taking this herb in conjunction with Levoxyl may increase the effects of the latter and aggravate a thyroid condition.

Bugleweed

Also known as Virginia water horehound and gypsy weed, bugleweed is used in traditional folk medicine to treat hypothyroidism and enlarged thyroid. The herb contains phenol compounds that suppress thyroid function and available levels of thyroid hormone T4, while large doses of the extract are used to decrease TSH. This means that this herb will likely counteract the effects of Levoxyl.

Makandi

Also known as Coleus forskohlii, or Indian coleus, this herb is used in traditional Ayurvedic medicine to regulate thyroid function. The plant contains a compound called forskolin that increases AMP-kinase, a major signaling enzyme involved in regulating how the thyroid uses iodine. A study published in "American Journal of Physiology, Cell Physiology" in June 2011 demonstrates that AMP-kinase is necessary for thyroid hormone production. Although this herb appears to be a promising therapy to support thyroid function, these results indicate that it should not be combined with pharmaceutical drugs such as Levoxyl.

Other Herb-Drug Interactions

Levoxyl may interact with a variety of other pharmaceutical medications and herbal medicines, particularly antidepressants and agents that lower blood pressure or produce estrogenic effects. Because this includes a wide range of herbs, including St. John's wort, ginkgo biloba and milk thistle, talk to your physician about your use of supplements before you begin taking this drug.