The cause of fibromyalgia is unknown; however, it is believed to involve a combination of genetic and environmental factors with half the risk attributed to each. The condition runs in families and many genes are believed to be involved.
Agonist: A substance that acts like another substance and therefore stimulates an action. Agonist is the opposite of antagonist. Antagonists and agonists are key players in the chemistry of the human body and in pharmacology.
Opiate agonists are drugs that mimic the effects of naturally-occurring endorphins in the body, and produce an opiate effect by interacting with the opioid receptor sites. Examples of opiate agonists include methadone and LAAM.n opiate antagonist is a drug that replaces opiate agonists at the receptor sites. This blocks the patient from experiencing the opiate effects of the agonist drug.