Since the combination pills are only available by brand name, and since generic versions of their ingredients are usually available, the combination pills are more expensive. And using fixed-combination pills offer less flexibility: so if the dose of one ingredient needs to be adjusted, both would end up being adjusted.

But the benefits of an easier routine may make the added cost worthwhile, if the combination is able to control your diabetes. For example, there may be less pills to swallow, and for people who have insurance for their medications, it's only a single copayment for the combination product.

The six classes of diabetes pills are:

1. sulfonylureas — glyburide (DiaBeta, Micronase), glipizide (Glucotrol, Glucotrol XR) glimeprimide (Amaryl), and many others.
2. biguanides —  metformin (Glucophage)
3. thiazolidinediones — (pioglitazone (Actos) and rosiglitazone (Avandia)
4. meglitinides — repaglinide (Prandin) and nateglinide (Starlix)
5. alpha-glucosidase inhibitors acarbose (Precose) and miglitol (Glyset)
6. DPP-4 inhibitors — sitagliptin (Januvia)

Available combination pills for diabetes:

• Combination of glyburide plus metformin: Brand name: GlucoVance (Bristol-Myers Squibb) (Approved by FDA July 31, 2000.)
• Combination of rosiglitazone plus metformin: Brand name: Avandamet (GlaxoSmithKline) (Approved by FDA October 10, 2002.)
• Combination of glipizide plus metformin: Brand name: Metaglip (Bristol-Myers Squibb) (Approved by FDA October 22, 2002.)
• Combination of metformin plus pioglitazone: Brand name: Actoplus Met (Takeda) (approved by FDA August, 2005.)
• Combination of Avandia plus Amaryl: Brand name: Avandaryl (GlaxoSmithKline) (approved by FDA November 23, 2005.)
• Combination of Amaryl plus Actos: Brand name: Duetact (Takeda) (approved by FDA July 28, 2006.)
• Combination of Januvia plus metformin: Brand name: Janumet (Merck) (approved by FDA April 2, 2007.)

Diabetes is one of the top 10 causes of death in the United States. Many patients take more than one tablet to control the disease, which is caused by a defect in the body's ability to produce or respond to insulin. "It will be easier for general practitioners to prescribe the combination pills, and physicians think it will help with patient compliance," said Carole deDios, author of the Decision Resources report.

Still, new types of single pills will dominate the market over the next decade, with such drugs as inhaleable insulin expected to gain share. That's because many specialist physicians prefer to have greater flexibility in dosing than a combination pill allows.

Type 2 diabetes, which represents about 90 percent of the total market for diabetes treatments is expected by analysts to grow to $13 billion in the major drug markets by 2011 from $6 billion in 2001. The disease is becoming more widespread with the increase, especially in the United States, of obesity. One already-marketed combination diabetes pill, Glucovance, is a combination of metformin and glyburide. It generated sales of $330 million in 2001, and deDios expects those to rise to $530 million over the next decade. Combinations awaiting approval include a GlaxoSmithKline Plc pill that combines the popular generically available metformin and Glaxo's Avandia, chemically known as rosiglitzone. Another combination, from Bristol-Myers Squibb Co. pairs metformin and another widely used drug, glipizide.