Rapidtard was a 75% Bovine NPH/isophane and 25% Porcine R/neutral/normal mixed insulin made by Novo Nordisk. The name appears to signify the insulin was a combination of Pork Actrapid and Bovine Insulatard, or NPH/isophane insulin. ^[2]

Mixed insulins cover a wide range as they can be animal origin, r-DNA/GE/GM origin or analog insulins. They can also vary in the fraction (amount or percent) of the two types (R/neutral and NPH/isophane) of insulin used to make a non-analog mix, and in the percentage of fast/rapid-acting analog insulin and slower-acting protamine suspended analog insulin.

For some reason, those in the US choose to list the slower, NPH/isophane based insulin fraction first, such as Humulin or Novolin 70/30. The rest of the world gives the faster insulin top billing and the result is 30/70. Regardless of how this is written, it means that the insulin is made up of 70% NPH/isophane insulin and 30% R/neutral insulin.

The most common mixes are 70/30 (30/70) (non analog) or 75/25 (25/75) (analog). There are no currently-marketed mixes which combine insulins of different origins. Eli Lilly's form of beef/pork Iletin and Novo Nordisk's Lentard were discontinued some time ago. Here are the most common ones that could cause confusion:

Non-Analog Mixed Insulins
	All Intermediate-acting
Insulin Is	Expressed As	Expressed As
10% R/Neutral Insulin 90% NPH/Isophane Insulin	90/10	10/90
20% R/Neutral Insulin 80% NPH/Isophane Insulin	80/20	20/80
30% R/Neutral Insulin 80% NPH/Isophane Insulin	70/30	30/70
40% R/Neutral Insulin 60% NPH/Isophane Insulin	60/40	40/60
50% R/Neutral Insulin 50% NPH/Isophane Insulin	50/50	50/50

ReferencesEdit

1. ↑ Maddison, Jill E.,Page, Stephen W.,Church, David B. (2008). Small Animal Clinical Pharmacology. Saunders Ltd..
2. ↑ Montgomery, DAD. Modern Insulin and Insulin Therapy. Royal Victoria Hospital-Belfast.