Fast-acting artificial insulin drugs work just as well as regular human insulin, but it’s unclear how they could affect the health of people with diabetes over the long run, according to a new review of recent studies.

The designer drugs, called insulin analogs, are a lab creation, different from human insulin by only a few protein building blocks. Insulin analogs with brand names like Humalog, Novolog and Apidra are absorbed more quickly than regular insulin, so diabetic patients can inject them right before or after eating to control their mealtime rise in blood sugar.

On average, people with type 1 diabetes who injected an insulin analog had slightly lower - one-tenth of 1 percent - blood sugar levels than those who used regular insulin, according to the review of 49 studies.

For type 2 diabetes patients, there was no real difference in blood sugar levels between those who used analog or regular insulin. There were also a similar number of low blood sugar episodes in both sets of patients, regardless of the type of insulin used, said Dr. Andrea Siebenhofer of the Medical University of Graz and colleagues.

“Our analysis suggests only a minor benefit of short acting insulin analogs in the majority of diabetic patients treated with insulin,” Siebenhofer said.

None of the studies in the review examined the possible long-term effects of insulin analogs, including how they may affect the health of people with diabetes-related complications such as heart disease and kidney failure. Until these effects are studied, there should be “a cautious response to the vigorous promotion of insulin analogs,” Siebenhofer warned.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

The Cochrane reviewers, several of whom have studied short and long-acting insulin analogs on behalf of pharmaceutical companies that sell the drugs, analyzed 49 studies involving 8,274 diabetes patients. Most of the participants were being treated for type 1 diabetes, and three-quarters of the studies used the analog Humalog.

Insulin analogs are more expensive than human insulin, but their popularity has grown since they were first approved in the United States by the Food and Drug Administration in 1996, according to diabetes researcher and family physician Dr. Michael Schooff of Clarkson Family Medicine in Omaha.

“Most endocrinologists I know believe in the ‘if it ain’t broke, don’t fix it’ philosophy, so if a patient is doing well on any insulin regimen, they are unlikely to change. On the other hand, I haven’t seen an endocrinologist start a newly diagnosed patient - or new to start on insulin -on a conventional insulin regimen. All of the new prescriptions I see are for very-rapid or long-acting analogs,” Schooff said. “Where the analogs have an advantage is in allowing the insulin regimen and delivery to fit easier into people’s life and lifestyle,” he said.

Schooff said rapid analogs also are the drugs most often available with insulin pumps, devices that deliver insulin through a small mechanical device worn on the body rather than through injections.

Although Siebenhofer and colleagues found few differences between analogs and regular human insulin therapy, they said the studies varied in what they measured and how they selected their patients, and were generally of poor quality, making it difficult to interpret their results.

“For safety purposes, we need a long-term follow-up of large numbers of patients who use short acting insulin analogs,” Siebenhofer said.

A. Siebenhofer et al. Short acting insulin analogues versus regular human insulin in patients with diabetes mellitus. The Cochrane Database of Systematic Reviews 2006, Issue 2.