Lufenuron is approved for use in dogs and cats 6 weeks of age and older for the control of ﬂea populations.
Lufeneron showed initial promise as a treatment for fungal infections, but the earlyenthusiasm has dampened considerably as efficacy appears doubtful.
Lufenuron acts by inhibiting chitin synthesis, polymerization, and deposition in ﬂeas, thereby preventing eggs from developing into adults. It is believed that lufeneron’s nonspeciﬁc effect on chitin synthesis is related to serine protease inhibition. Lufeneron’s mechanism of action, theoretically, would also have effect on fungi.
Adverse effects reported in dogs and cats after oral lufenuron include: vomiting, lethargy/depression, pruritus/urticaria, diarrhea, dyspnea, anorexia, and reddened skin. The manufacturer reports that the adverse reaction rate is less than 5 animals in one million doses.
Chitin is found in the supporting structures of many organisms. Of relevance to microbiology, chitin is present in fungal species such as mushrooms, where it can comprise from 5% to 20% of the weight of the organism.
orally-administered pills can sometimes cause an upset stomach with acid reflux.
Lufenuron is thought to be an effective anti-fungal in plants. It is safe because Lufenuron is biochemically inert to mammals. Lufenuron is not broken down by the liver or kidneys.Lufenuron's antifungal property may be due to its inhibiting the synthesis of chitin, which makes up roughly 33% of the typical fungal cell wall.
Lufenuron was included in a biocide ban proposed by the Swedish Chemicals Agency because it is toxic to fresh water zooplankton  and approved by the European Parliament on January 13, 2009.
Chitin synthesis inhibitors share a similar chemical structure as other benzoylphenyl ureas.Their mode of action is by interfering with the polymerization pathway of chitin, inducing accumulation of the monomer uridine diphospho-N-acetylglucosamine and blocking its synthesis (Beeman 1982).
The final step of chitin biosynthesis is the polymerization of N-acetylglucosamine
from the activated substrate UDP-N-acetylglucosamine, by the enzyme chitin synthase (EC 18.104.22.168). This enzyme has been well studied in fungi and yeasts (Gooday
Leighton e t al. (1981) have proposed that diflubenzuron acts indirectly on chitin synthase by inhibiting a proteolytic enzyme required for its activation from the zymogen form.
Next to cellulose, chitin is the most important biopolymer in nature. It is produced by numerous species belonging to different taxonomic groups, including fungi, molluscs and
arthropods. The ability to form chitin strictly depends on the expression of chitin synthase (EC 22.214.171.124),
Lufenuron is a benzoylphenylurea drug that interferes with chitin synthesis. It is used in veterinary medicine as a ﬂea prophylactic product, due to its non-speciﬁc inhibitory effect on chitin synthesis, probably related to serine protease inhibition.³
REASONS NOT TO USE THIS ARE TOO STRONG IN MY OPINION.
An unexpected result of lufenuron treatment was the inhibition of midgut epithelial cell differentiation. At concentrations of 0.5 and 1.0 ppm, partially differentiated epithelial cells were seen in the midgut of blood-fed fleas along with fully differentiated cells.
Micrographs of ovaries, from animals treated with lufenuron, showed some space between the follicular epithelium and the oocyte membrane. The in vivo incorporation of radioactive N-acetylglucosamine into chitin was inhibited by the presence of lufenuron.
The studies above demonstrate that Lufenuron can cause intestinal cell line damage and leaky gut. One benefit of the intestinal cells is that they regenerate quickly, thus demonstrating their ability to heal and restore the intestinal barrier. Lufenuron has the ability to block this regeneration. It's role in serine protease inhibition could lead to chronic inflammatory conditions, food allergies, autoimmune diseases, etc.
Lufenuron can also interfere with absorption of N-Acetylglucosamine, necessary for the formation of the cell walls in many beneficial bacteria.
Disturbance of the epithelial barrier and epithelial transport processes is often discussed to be a major factor in the pathogenesis of intestinal inflammation and inflammatory bowel disease. Increased permeability of the epithelial barrier in ulcerative colitis was first reported in 1973 .
How Bacteria-Induced Apoptosis of Intestinal Epithelial Cells Contributes to Mucosal Inflammation
The intestinal epithelium provides a critical protective barrier against enteric pathogens, food antigens, and physiochemical stresses caused by digestive and microbial products, and yet must be selectively permeable to beneficial nutrients and fluids. Tightly regulated control of barrier function and integrity is critical, as the pathogenesis of intestinal diseases such as Crohn's disease, ulcerative colitis, inflammatory bowel diseases (IBD), and autoimmune diseases are linked to intestinal barrier dysfunction and increased intestinal permeability (1). The intestinal epithelium is a single layer of linked columnar epithelial cells that regulates, through the paracellular pathway, the selective passage of ions, fluid, and macromolecules from the intestinal lumen into the underlying tissues.
The intestinal epithelium serves as a major protective barrier between the mammalian host and the external environment. Here we show that the transmembrane serine protease matriptase plays a pivotol role in the formation and integrity of the intestinal epithelial barrier. St14 hypomorphic mice, which have a 100-fold reduction in intestinal matriptase mRNA levels, display a 35% reduction in intestinal transepithelial electrical resistance (TEER). Matriptase is expressed during intestinal epithelial differentiation and colocalizes with E-cadherin to apical junctionalcomplexes (AJC) in differentiated polarized Caco-2 monolayers. Inhibition of matriptase activity using a specific peptide inhibitor or by knockdown of matriptase by siRNA disrupts the development of TEER in barrier-forming Caco-2 monolayers and increases paracellular permeability to macromolecular FITC-dextran. Loss of matriptase was associated with enhanced expression and incorporation of the permeability-associated, “leaky” tight junction protein claudin-2 at intercellular junctions. These results support a key role for matriptase in regulating intestinal epithelial barrier competence, and suggest an intriguing link between pericellular serine protease activity and tight junction assembly in polarized epithelia.
“Mechanisms terminating the short physiological life cycle of epithelial cells are supposed to have an impact on these essential functions and have influence on inflammatory reactions in the intestinal mucosa. A disturbance of the epithelial barrier is thought to be a major factor in the pathogenesis of inflammatory bowel disease.
Disturbance of the epithelial barrier and epithelial transport processes is often discussed to be a major factor in the pathogenesis of intestinal inflammation and inflammatory bowel disease.”
One website that sells lufenuron has pictures of inflammatory skin conditions that responded to lufenuron treatment. A deficiency of serine protease inhibitors can play a role in creating such inflammatory skin conditions. The website implies that the healing seen in the pictures was created by lufenuron's anti-fungal affect against candida. It is much more likely that this was due to its serine protease inhibition effect. I've talked frequently about how people misinterpret what they see and notice. This would be a classic example.
Lufenuron has demonstrated the ability to damage intestinal cells and intestinal cell junctions. Intestinal cells play a critical role in the maintenance of the homeostasis of the intestinal tract. Lufenuron can also interfere with the structure of healthy intestinal bacteria. It has demonstrated a possible role in affecting candida fungal growth. The goal of any approach in restoring balance to the intestinal flora, immune responses, and candida overgrowth, should not also present known risks to the body. Based on this, I would never recommend lufenuron.