In fact, several other amino acid exchanges have been tried and met with unacceptable side effects. Gastroparesis is a condition caused by neuropathy which causes the stomach to empty slowly and erratically. Acarbose is a drug which slows the absorption of carbohydrates from the intestine. Either may result in lispro insulin acting too quickly. Response to lispro is variable.
Some patients love it, others hate it.
On the average, it does not change bg control either for better or for worse, but some patients definitely find it one or the other. Eli Lilly is promoting lispro for convenience, not for better control. Doctors and patients are still experimenting with the best regimens for using lispro insulin. Typically lispro insulin is injected very close to mealtime. An obvious concern is that hypoglycemic reactions might be more common with a faster acting insulin.