Source: Health Products and Food Branch (CA) Revision Year: 2012
The efficacy of NYDA is exclusively based on a physical mode of action. This is important given the resistance present for current pesticide therapies approved in Canada.8 The “point of attack” of the physical mode of action of NYDA is the insect’s respiratory system. NYDA works by suffocating the lice, nymphs and the embryos in the eggs. The unique physical properties including the viscosity and creeping/spreading properties of this solution allow it to readily flow into the breathing system of all developmental stages of the insect, thus leading irreversibly to suffocation and death.1,3 It creeps through the stigmata (spiracles) deep into the tracheae of the head lice as well as through the aeropyles of the operculum of the eggs inside the eggs. When it reaches there, the solution displaces the air (oxygen). The low viscosity, volatile dimeticone enables the NYDA solution to penetrate into the breathing system. Its evaporation causes the thickening of the NYDA solution. The remaining high viscosity dimeticone finally seals the respiratory system and thus leading to suffocation of all stages of head lice (adult lice, larvae and eggs). This mode of action prevents development of resistance.
Studies done with house crickets and lice demonstrate a close correlation between death of the lice and the influx of the solution into the head tracheae. This strongly suggests that the complete filling of the head tracheae effectively and immediately blocks the oxygen supply of the central nervous system. Death, following various phases of disability after the entrance of dimeticones into the abdominal tracheal system, reflects the sequence of oxygen deprivation. This is further supported by the fact that NYDA had no effect on the insect when applied solely to the outside of the head or mouth. If the solution had a chemical neurotoxic effect, similar to permethrin or other chemical insecticides, one would expect mortality to occur upon contact, regardless of where the solution is applied on the body of the insect.
The studies outlined in the Table below have been completed with NYDA.
| Title | Purpose |
|---|---|
| In vitro studies to demonstrate physical mode of action | Demonstrate that NYDA works by a physical mode of action; show that the fragrance components have no impact on the pediculicidal effect. |
| In vitro Study on the Efficacy of the Dimeticone-Based Pediculicide NYDA and of Three Reference Medical Products Against Human Head Lice (Pediculus humanus capitis) | Examination of the pediculicidal efficacy of NYDA in comparison to three reference products. |
| Comparative in-vitro Study on the Efficacy of Five Head Lice Products Against Human Head Lice | Examination of the pediculicidal efficacy of NYDA in comparison to four reference products. |
| Ovicidal Efficacy of NYDA, Infectopedicul, Mosquito Lauseshampoo, Goldgeist forte and Etopril against Young and Mature Eggs of Human Head Lice | Examination of the ovicidal efficacy of NYDA on young and mature eggs of head lice in comparison to several other lice treatments. |
| Ovicidal response of NYDA formulations on the human head louse (Anoplura: Pediculidae) using a hair tuft bioassay | Demonstrate 100% ovicidal effect after 8-h exposure of the eggs of the permethrinresistant human head lice. |
The following studies have been conducted with NYDA.
| Test | Result | Test article | Conclusion |
|---|---|---|---|
| Cytotoxicity | None of the extract concentrations showed any cytotoxic reactions. | NYDA without fragrances | NYDA without fragrances is not cytotoxic. |
| Irritation (Intracutaneous Reactivity) | No irritant effects on intact skin after a contact time of 4 hours. | NYDA | No irritant/corrosive effects and NYDA is classified into the lowest response category (negligible). |
| Sensitization | The test item caused no reactions identified as sensitization. | NYDA | No sensitizing properties. |
| Acute Eye Irritation | Slight irritation (Redness of conjunctivae (grade 1)) in 2 out of 3 test animals at 24 hours post instillation, changes were fully reversible within 48 hours. | NYDA | Not an-eye irritant. |
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