What is lindane?
Healthcare vs. Agricultural Uses
In the 1940s, lindane was registered with the U.S. Department of Agriculture (USDA) for agricultural use, and in 1951 it was approved by the Food and Drug Administration (FDA) for medical use in the treatment of scabies, head lice and pubic lice (crabs).1,2 Comparatively, more than 99% of all lindane sold in the U.S. has been for agricultural purposes.3 (See 2006 EPA RED on Agricultural Lindane)
<1% of lindane use in the U.S. has been for medical purposes3
Hexachlorocyclohexane (HCH) exists as eight (8) distinct forms, or isomers4
Lindane belongs to a group of related compounds described chemically as hexachlorocyclohexanes, or HCH. There are several different forms (or isomers) of HCH. Lindane is the gamma form.
Different isomers have different properties:3,5
- Isomers are variations of a single molecule that share the same chemical formula, but have different three-dimensional structures
- Because of their different structures, each isomer of HCH has different chemical properties and different safety profiles
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The most relevant forms of HCH to public health and the environment include:3
- Alpha-HCH
- Beta-HCH
- Gamma-HCH (i.e., lindane)
Lindane should not be mistaken for other forms of hexachlorocyclohexane (HCH)
It is important to distinguish gamma-HCH (i.e., lindane) from other forms of HCH, since some of the environmental and health claims made about lindane by those wishing to ban its use may, in fact, apply primarily or exclusively to non-gamma forms.
Alpha- and beta-HCH are the most toxic forms
- Alpha- and beta-HCH are notably the more toxic isomers and are the dominant forms found in the environment3,5
- Alpha- and beta-HCH are also the most common forms of HCH found in animal and human tissues and fluids3,5
- Lindane (i.e., gamma-HCH) is the only isomer with insecticidal activity3; alpha- and beta-HCH provide no value to agriculture or healthcare
Lindane medications contain pharmaceutical-grade gamma-HCH
- Lindane medications have always been formulated with pharmaceutical-grade lindane—a highly purified form of gamma-HCH
- Technical-grade HCH—a mixture of alpha-HCH (60%–70%), beta-HCH (5%–12%), and gamma-HCH (10%–15%)—was used agriculturally in the U.S. until 1978 but is still used in other parts of the world3
- Technical-grade HCH has never been used in medicine
Occupational exposure and patient safety are different issues
Occupational exposure to lindane is a separate issue from exposure resulting from approved medical uses. Occupational exposure relates to agricultural use of lindane and chronic exposure of farm workers who handle seeds pre-treated with agricultural-grade lindane, or those working in seed-treatment facilities. A major focus of the Environmental Protection Agency's (EPA’s) assessment of lindane safety has related to agricultural uses and occupational exposure.2 (See 2006 EPA RED on Agricultural Lindane)
Occupational exposure vs. medical application:
- Occupational exposure to lindane poses different risks of potentially greater concern, since workers may be exposed to high and persistent concentrations of lindane2,6
- In contrast, lindane medications are applied in relatively small amounts and in low concentration, typically as one-time treatments7,8
- Moreover, there are no health benefits that result from occupational exposure to lindane2
- FDA Lindane Assessment Memorandum:6
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“This risk of occupational/environmental exposure should be assessed separately and independent of the risk related to the therapeutic use of a medication to treat a medical condition where there is direct benefit to the patient”
The FDA and the EPA have affirmed the safety of lindane medications
Since their introduction to the U.S. healthcare market in 1951, lindane medications have undergone repeated and comprehensive reviews by medical and scientific subject matter experts working with the FDA and the EPA. Consistently, expert reviewers have concluded that lindane medications do not pose a significant risk to public health or public safety when used as currently labeled.2,6
Lindane Lotion, 1% USP is FDA approved for the treatment of scabies; Lindane Shampoo, 1% USP is FDA approved for the treatment of head lice and pubic lice (crabs). Both prescription medications are indicated second line, meaning they are used when other first-line medications have failed or cannot be tolerated.7,8
- Regulatory Viewpoints on Lindane Medications
Please See Important Safety Information
References:
- U.S. Food and Drug Administration (FDA). FDA Public Health Advisory: Safety of Topical Lindane Products for the Treatment of Scabies and Lice. March 28, 2003. Available at: http://www.fda.gov/cder/drug/infopage/lindane/lindanePHA.htm.
- U.S. Environmental Protection Agency (EPA). Lindane Reregistration Eligibility Decision (RED). 2002. Available at: http://www.lindane.com/pdf/lindane_epa_2002.pdf.
- Commission for Environmental Cooperation. The North American Regional Action Plan (NARAP) on Lindane and Other Hexachlorocyclohexane (HCH) Isomers. 2005. http://www.cec.org/files/PDF/POLLUTANTS/Lindane-NARAP-Public-Comment_en.pdf.
- U.S. Centers for Disease Control and Prevention (CDC) Agency for Toxic Substances and Disease Registry. Public Health Statement for Hexachlorocyclohexane. 2005. Available at: http://www.atsdr.cdc.gov/toxprofiles/phs43.html.
- Commission for Environmental Cooperation. Decision Document on Lindane Under the Process for Identifying Candidate Substances for Regional Action Under the Sound Management of Chemicals Initiative. April 19, 2000. Available at: http://www.cec.org/files/pdf/POLLUTANTS/linddd_en.pdf.
- U.S. Food and Drug Administration (FDA). Lindane Assessment Memorandum. Posted 2003. Available at: http://www.fda.gov/cder/drug/infopage/lindane/lindanememoassessment.pdf.
- Lindane lotion, USP, 1% prescribing information. Updated March 28, 2003. Available at: http://www.fda.gov/cder/foi/label/2003/006309lotionlbl.pdf.
- Lindane shampoo, USP, 1% prescribing information. Updated March 28, 2003. Available at: http://www.fda.gov/cder/foi/label/2003/006309shampoolbl.pdf.
