Eli Lilly brand name for their mix of 25% insulin lispro and 75% insulin lispro protamine suspension. Also known as Humalog Mix 25, it is an intermediate-acting insulin. The 75% fraction that is NPL (Neutral Protamine Lispro) is a suspension of crystals formed by combining insulin lispro and protamine. A study of dogs from 1993-1994 using various fractions of Humalog mixes against human NPH/isophane insulin found only minor differences in the use of Humalog Mix as opposed to NPH/isophane insulin.