Fenvalerate is type II pyrethroid and widely used pesticide. Fenvalerate is listed under Class IV of the U.S. Food and Drug Administration (USFDA) Surveillance Index Classification, indicating a low hazard potential to humans from both exposure and toxicological standpoints. Fenvalerate irreversibly prolongs the sodium current during depolarization. The sensitization of sodium channels, probably tetrodotoxin-resistant (TTX-R) sodium channels, by the long-term activation of protein kinase C may play an important role in the enhancement of the duration of fenvalerate-induced nociceptive behavior in diabetic mice. Fenvalerate inhibits testosterone synthesis via pathways involving intracellular Ca(2+) and circadian clock genes (Bmal1, Rev-Erb alpha, Ror alpha) as well as StAR mRNA expression in TM3 cells. It potently inhibits human CYP2D6 and moderately CYP3A4. Fenvalerate has an anxiolytic effect on rats.