The dose-proportional, intraindividual, single- and repeated-dose pharmacokinetics of roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor under investigation for chronic obstructive pulmonary disease and asthma, was investigated in healthy subjects. In an open, randomized, 2-period, 2-sequence crossover study, 15 subjects received immediate-release tablets of roflumilast 250 or 500 microg as single (day 1) and as repeated, once-daily doses for 8 days (days 5-12). Dose-adjusted point estimates and 90% confidence intervals of test (500 microg)/reference (250 microg) ratios for AUC and Cmax of roflumilast and its pharmacologically active N-oxide metabolite after single and repeated dosing were all within the standard equivalence acceptance range (0.80, 1.25) indicating dose proportionality. The pharmacokinetic properties of both roflumilast dosage forms provide clinically relevant evidence of predictable, intraindividual total (AUC) and maximum (Cmax) exposure of roflumilast and roflumilast N-oxide. Repeated oral dosing with roflumilast 250 and 500 microg once daily was well tolerated.

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Many insecticides are inactive on their target sites in the form that is sold and applied, needing first to be bioactivated. This proinsecticide strategy has often been achieved by design, through systematic derivatization of intrinsically active molecules with protecting groups that mask their toxic effects until their selective removal in target insects by metabolic enzymes generates the toxiphore. Proinsecticides can be designed to gain selectivity between target and non-target organisms, or to improve bioavailability by enhancing plant or insect uptake. In most cases, however, chance trumps design in proinsecticide discovery: most first-in-class products that we now know to be proinsecticides were only discovered a posteriori to be such, often after having been on the market for years. Knowing the active form of an insecticide is essential to mode of action identification, and early mode of action studies on novel chemotypes should take into account the possibility that the compounds might be proinsecticides. This paper reviews examples of proinsecticides in the marketplace, strategies for making proinsecticides and techniques for unmasking proinsecticides in mode of action studies. Our analysis of global agrochemical sales data shows that 34% of the dollar value of crop insecticides used in 2015 were proinsecticides. © 2016 Society of Chemical Industry.

Pro‐insecticides have been a significant part of the insecticide market for decades. Bioactivation of such compounds is generally an enzyme‐controlled process, in which the target insect metabolizes the pro‐form into an active compound. This approach has several potential advantages, including improved bio‐kinetic properties and safety profiles of the pro‐insecticide relative to the active form. A less common advantage of pro‐insecticides is increased activity on metabolically resistant strains. Specific cases in which a pro‐insecticide demonstrates negative cross‐resistance (NCR) on a metabolically resistant strain due to increased bioactivation of the pro‐insecticide have been noted sporadically over the past 50+ years but have not been reviewed before. The purpose of this mini‐review is to catalog the cases in which a pro‐insecticide demonstrated improved activity on an insect strain resistant to a second insecticide via a metabolic mechanism. Cases are relatively rare, but where it does occur the mechanism of NCR is generally recognized as being due to the increased metabolic activity of the resistant strain. These observations can provide learnings with potential application for resistance management if the correct pro‐insecticide is selected for a resistant strain which is better able to bioactivate it. A better understanding of the bioactivation of pro‐insecticides by resistant insects could also aid in insecticide discovery, potentially leading to improved pro‐insecticide design. © 2021 Society of Chemical Industry

The efficiencies of three extraction techniques for removal of nonpesticidal organophosphates from soil were determined. Traditional Soxhlet extraction was compared to supercritical fluid extraction (SFE) and a low solvent volume flow through technique referred to here as high-pressure solvent extraction (HPSE). SFE, optimized by varying parameters of temperature, pressure, and methanol polarity modifier, showed at least 90% efficiency in the extraction of OPs from both spiked and native soils. HPSE experiments showed efficient and consistent recoveries over a range of temperatures up to 200 °C and pressures up to 170 atm. Recovery of TCP from spiked soils with HPSE depends on the system variables of temperature and pressure, which dictate density and flow rate. HPSE provided extraction efficiencies comparable to those obtained with Soxhlet extraction and SFE but with substantial savings of time and cost.