US Pharm. 2006;5(Student suppl):8-9.

Characterized by increased levels of blood glucose, diabetes mellitus (DM) results from defects in insulin production, insulin action, or both and is classified based upon the underlying cause.1 Type 1 DM, also known as insulin-dependent DM or juvenile-onset diabetes, accounts for approximately 5% to 10% of all cases. The majority of diagnosed cases are type 2 DM, commonly referred to as non–insulin-dependent DM or adult-onset diabetes. This form of diabetes may be associated with older age, obesity, genetics, history of gestational diabetes, impaired glucose tolerance, physical inactivity, and/or ethnicity. Studies demonstrate that African-Americans, Hispanic-Americans, American Indians, and some Pacific Islanders are at a higher risk for diabetes and that adolescents are increasingly affected by diabetes as a result of obesity.1,2 Also, during pregnancy, 2% to 5% of women are diagnosed with gestational diabetes, after which they have a 40% chance of developing diabetes within five years.1 Symptoms of diabetes typically include poly­ uria, polydipsia, polyphagia, weight loss, or blurred vision.2,3 Diagnostic guidelines for diabetes are listed in table 1.


Glycemic Control
Research concludes that improved glycemic control is ultimately beneficial for both types of diabetes. In general, for a 1% reduction in hemoglobin A1C, the risk of developing microvascular complications (e.g., hypertension, stroke, neuropathy, kidney disease) is reduced by about 40%.2 Early detection and treatment of diabetes may also decrease the risk of severe vision loss by 50% to 60% and kidney failure by 30% to 70%.3 Additionally, it may alleviate symptoms of diabetes-induced neuropathy.3 This explains the annual global cost for glucose testing, $3.7 billion, with a growth rate of 12% to 18%.3

Currently, diabetic patients must frequently monitor their glucose levels by pricking their fingertip to draw a drop of blood. Unfortunately, the invasive nature of this procedure often results in patient complaints and noncompliance. With this in mind, several companies have created noninvasive glucose monitors. Among this new class is SpectRx's Real-Time Glucose-Sensing System (RTGSS), as seen in figure 1.



Real-Time Glucose-Sensing System
The RTGSS measures glucose from transdermal fluid (TDF) using a subcutaneous sensor (figure 2) over a 24- to 72-hour period.4,5 The TDF collection procedure involves the application of a focused laser beam to the arm or abdomen (preferable sites) to produce micropores in the stratum corneum of less than 100 micrometers in diameter. A small, flexible disk containing an energy-absorbing dye is aligned with a handheld laser that produces pulsed laser energy over three-second intervals. Once the micropores have been created, the site is covered with a single-use TDF harvesting patch attached to a continuous vacuum that attracts TDF to the glucose sensor. The vacuum generates a continuous flow of about 5 to 15 mcL/min, and any excess fluid is stored in a waste depot within the patch. Since the sensor is external, it insulates the RTGSS from the body's natural immune response. Patient instructions are found in table 2.



Clinical Efficacy
Measurement of glucose from interstitial fluid reportedly produces glucose concentrations similar to venous blood or plasma following an oral glucose challenge. Since the glucose content of TDF is comparable to that of plasma glucose, it may serve as a surrogate for blood glucose.6


A double-blinded clinical trial examined the efficacy of the RTGSS. Its results were subsequently published in Diabetes Technology and Therapeutics in June 2005.4 The study's subjects included various ethnic and age-groups and both sexes. A small number of participants did not have diabetes and served as a control group. The BarbaraDavisCenter for Childhood Diabetes in Denver and the SpectRx clinical facility in Norcross, Georgia, enrolled 110 subjects. Results showed that continuous glucose monitoring using the RTGSS improved metabolic and glycemic control. Pediatric subjects tolerated the procedure with no sequelae from the poration process, and there was no incidence of associated skin infections. The study also demonstrated that RTGSS could obtain sufficient TDF from a single laser poration for at least 48 hours before the healing process closed the pores.

Conclusion
Although currently unavailable for purchase, transdermal measurement of glucose shows great promise as a noninvasive method for monitoring. This may increase patient compliance and decrease costs associated with uncontrolled glucose. For more information, see SpectRx's Web site (www.spectrx.com) or call (770) 242-8723.

REFERENCES
1. DiPiro T, Talbert R, Yee G, et al, eds. Pharmacotherapy: A Pathophysiologic Approach. 5th ed. New York: McGraw-Hill; 2002:1335-1355.
2. American Diabetes Association. Diabetes facts and figures. Available at: www.diabetes.org/diabetes-statistics/national-diabetes-fact-sheet.jsp.
3. CDC. Preventing diabetes complications. Available at: www.cdc.gov/diabetes/pubs/general.htm#top. Accessed August 18, 2005.
4. Burdick J, Chase P, Faupel M, et al. Real-time glucose sensing using transdermal fluid under continuous vacuum pressure in children with type 1 diabetes. Diabetes Technol Ther. 2005;7:448-455.
5. SpectRx Inc. The real-time glucose-sensing system. Available at: www.spectrx.com.
6. Gebhart S, Faupel M, Fowler R, et al. Glucose sensing in transdermal body fluid collected under continuous vacuum pressure via micropores in the stratum corneum. SpectRx Publication, 2002.

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