Accounting for plasma levels below detection limits in a one-compartment zero-order absorption pharmacokinetics model

We provide a simple method for fitting a one-compartment, zero-order absorption pharmacokinetics model in the presence of observations below the detection limit. This method may be extended to more complex pharmacokinetics models. We demonstrate, using a small simulation study, that the method provides accurate parameter estimates over a range of detection limits and we compare it to an ad hoc midpoint method. An applied example is provided from a pharmacokinetic investigation of a nicotine nasal spray.