Physicochemical Properties and Formulation

The active ingredient of pyriproxyfen is an odorless white crystal with a melting point of 48.1 °C. Its vapor pressure is below 1.0 x 10 mmHg (22.8 °C) and its solubility in water at 25 °C is 0.367 ppm. 

Pyriproxyfen is stable and hardly decomposes even if kept at 50 °C for six months. It is easily decomposed by higher pH and higher temperature. Moreover, although pyriproxyfen is promptly decomposed by ultraviolet rays, decomposition by sunlight ( 290 nm) was slight. 

An emulsifiable concentrate and granules are sold as formulations containing pyriproxyfen. The tape formulation is also sold in Japan under the trade name of Lano . The physicochemical properties of the formulations are very good and storage stability is very good. Moreover, mixtures with various insecticides have also been developed and sold. 

The very favorable mammalian toxicity, the animal and plant metabolism, environmental toxicity and residue, and the effect on non-target organisms are described in a technical report [34]. 

It is also sold as Sumilarv granules (0.5% content of pyriproxyfen) to control mosquito and housefly larvae for household use, and the sale was later expanded to control midges in Japan. In other countries it was also developed to control mosquitoes and houseflies, and sold as Sumilarv 0.5% granules. In addition, it has been developed for home and PCO uses and was registered with the EPA in 1995. 

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The physicochemical properties of the drug are critical in the design of the dosage form. Solubility, stability, and pH can strongly affect whether a drug can be delivered effectively from a controlled delivery device. Because sustained-release devices often contain multiple doses that if released immediately would reach toxic levels, the physicochemical properties and formulation process may have to be more tightly controlled compared with immediate-release systems. 

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