Definition of "tricyclic" [tricyclic]

• Having or being a molecular structure that contains three closed rings: a tricyclic molecule. (adjective)
• A tricyclic antidepressant drug. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Another group of drugs, called tricyclic antidepressants are also prescribed for migraine prevention even though they're not approved by the FDA for this purpose."
• "BMJ finds that an older group of drugs known as tricyclic antidepressants may sometimes be safer in people over the age of 65."
• "In a study of almost 15,000 people in Scotland, British researchers found that older so-called tricyclic anti-depressants, such as Norpramin made by Sanofi-Aventis, were linked with a 35 percent increased risk of developing cardiovascular disease."