We examine some of the challenges associated with generating input signals for identifying dynamics in pain treatment interventions while imposing "patient-friendly" constraints on the design. Standard clinical trials, while providing some useful information, are not the most suitable vehicle for understanding the dynamic response of dosage changes to participant response. Meanwhile, much of the work in classical input design, even that which incorporates "plant-friendly" considerations, may not result in clinically acceptable trials for human participants. In this paper, we describe some of the issues involved and suggest various approaches (leading ultimately to optimization-based formulations) to obtain input signals with desired spectral properties under time-domain constraints of importance to clinical practice. Numerical examples are shown to illustrate the proposed method with a hypothetical clinical trial of the drug gabapentin for the treatment of neuropathic pain.