Benoxaprofen - Toxicokinetics

Toxicokinetics

Benoxaprofen is absorbed well after oral intake of doses ranging from 1 up to 10 mg/kg. Only the unchanged drug is detected in the plasma, mostly bound to plasma proteins. The plasma levels of benoxaprofen in eleven subjects have been accurately predicted, based on the two-compartment open model. The mean half-life of absorption was 0.4 hours. This means that within 25 minutes, half of the dose is absorbed in the system. The mean half-life of distribution was 4.8 hours. This means that within 5 hours, half of the dose is distributed throughout the entire system. The mean half-life of elimination was 37.8 hours. This means that within 40 hours, half of the dose is excreted out of the system.

In female rats, after oral dose of 20 mg/kg, the tissue concentration of benoxaprofen was the highest in liver, kidney, lungs, adrenals and ovaries. The distribution in pregnant females is the same, while it can also be found –in lower concentrations– in the foetus. There is a big difference between species in the route of excretion. In man, rhesus monkey and rabbit it is mostly excreted via the urine, while in rat and dog is was excreted via biliary-faecal excretion. In man and dog, the compound was excreted as the ester glucuronide, and in the other species as the unchanged compound. This means no major metabolic transformation of benoxaprofen takes place.