Figure 1.

Structure of the subcutaneous insulin absorption kinetic model. The model is characterized by a common hexameric state compartment for regular insulin (RI), neutral protamine Hagedorn (NPH) insulin, and lente insulin (x_h), whereas those for insulins glargine and ultralente (x_h,ulen and x_h,gla) are separate. A crystalline state compartment for NPH (c_NPH), lente (c_len), and ultralente (c_ulen) insulins and a precipitate compartment for insulin glargine (p_gla) model these protraction mechanisms. All insulin flows through a common a dimeric–monomeric state compartment (x_dm), interstitium compartment (x_i), and finally into the plasma (I). Adapted from Wong et al.²²