Insulin administration: present strategies and future directions for a noninvasive (possibly more physiological) delivery

Abstract

Insulin is a life-saving medication for people with type 1 diabetes, but traditional insulin replacement therapy is based on multiple daily subcutaneous injections or continuous subcutaneous pump-regulated infusion. Nonphysiologic delivery of subcutaneous insulin implies a rapid and sustained increase in systemic insulin levels due to the loss of concentration gradient between portal and systemic circulations. In fact, the liver degrades about half of the endogenous insulin secreted by the pancreas into the venous portal system. The reverse insulin distribution has short- and long-term effects on glucose metabolism. Thus, researchers have explored less-invasive administration routes based on innovative pharmaceutical formulations, which preserve hormone stability and ensure the therapeutic effectiveness. This review examines some of the recent proposals from clinical and material chemistry point of view, giving particular attention to patients' (and diabetologists') ideal requirements that organic chemistry could meet.

Keywords: biodegradable polymers; drug administration routes; drug formulations; insulin; nanoparticles; portal system; type 1 diabetes mellitus.

Figure 1

Schematic representation of the amino acid sequence of the human preproinsulin (A) and the conversion of proinsulin into biologically active insulin and C-peptide (B).

Figure 2

Portal-systemic blood insulin gradient and alternative routes of insulin administration.