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[IP] Site life, Humalog, Novolog

> At the risk of being hurled a slew of newbie darts, can anyone
> please tell me if Humalog insulin causes site problems and why and
> what the difference between Humalog and Novolog are? I've gotten the
> impression from various posts that the former is true but it was
> never quite clear.

Approximately 6% of pumpers that use Humalog suffer some side effects 
that appear to reduce site life to something like 36-48 hours, 
after which bg's begin to rise and the site becomes very resistant to 
additional insulin infusion. Moving the site appears to alleviate the 
problem. The overall result appears to be a localized (at the site) 
resistance to insulin that makes control very difficult. Mixing 
another insulin, usually Velosulin however a few pumpers us regular, 
seems to alleviate the symptoms and allow the infusion sites to 
function as well and as long as using regular or velosulin alone.

If you check the ABOUT page of the web site, you will see the 6% 
number for "mixers" and that most people that mix us 5 parts of 
Humalog and 1 part Velosulin. Your next question will be "what is 
Velosulin" :-)   --- It is a regular insulin that was developed with 
specific buffers for use in insulin pumps. In most other respects it 
behaves pretty much like regular insulin.

It is thought by one researcher that the sensitivity to Humalog is
brought about by a complex chemical interaction with the infusion
tubing and that mixing small amounts of regular or Velosulin with
Humalog somehow prevents the interaction or scavenges the offending
molecules. That research is not published. Novolog is chemically
different than Humalog and would probably not enter into the same
chemical interaction with the tubing. 

Neither Humalog nor Novolog are true insulins, they are insulin 
analogs. They differ in that both have certain amino acids modified or
switched in their molecular chains. In Humalog, the amino acids in
positions 28 and 29 on the insulin B-chain are reversed. In Novolog, a
single substitution of the amino acid proline with aspartic acid is
made at position 28 in the insulin B-chain.

So far a half dozen or so of our "mixer" pumpers have switched to 
straight Novolog with good success. One person has reported that 
Novolog does not see to work well for her. Since there are few users 
of Novolog at this time, it is not known if there is a similar subset 
of individuals that may have sensitivity to the composition of

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