Biguanides

Metformin (brand name: Glucophage) is a biguanide (by-GWAN-ide) that acts in several ways to control diabetes. It helps a patient's body use insulin better, and it helps the liver make less sugar and lowers the amount of sugar his body absorbs from food. This inexpensive drug, available since the mid-1990s, is commonly taken twice a day. A once-a-day, slow-release pill is also available. Metformin may also decrease LDL or "bad" cholesterol and triglycerides. This is often the first choice of treatment for older adults with type 2 diabetes.

Potential side effects: Metformin may trigger nausea and diarrhea, though this is less likely if a patient takes the drug with food or if he starts with a low dosage that's gradually raised as needed. This medication isn't recommended for people with certain kidney or liver problems, and those who take it should have regular kidney function checks, especially since the elderly are more prone to reduced kidney function.

It's not recommended for people over the age of 80 unless they've had a kidney function test. "I'm cautious about using metformin in my very elderly patients because of kidney problems," says endocrinologist Karen Earle, medical director of Center for Diabetes Services at California Pacific Medical Center in San Francisco. "When I do prescribe it to patients over 80, I make sure they don't just have a blood test but a more precise urine test to check kidney function."

Some people develop anemia (a blood disease) as a result of taking this drug, so a blood test in the first few months of therapy is also wise. Metformin may not be suitable if a patient has severe heart disease or drinks alcohol to excess.

Meglitinides

Repaglinide (brand name: Prandin) is in a class of drugs known as meglitinides (meh-GLIT-in-ides). This relatively new, considerably more expensive prescription medicine helps a patient's pancreas make more insulin and is typically taken before breakfast, lunch, and dinner.

Potential side effects: This drug, as with any blood-sugar-lowering medication, may make blood glucose go too low and cause hypoglycemia, which the elderly are already more prone to experience. It may also cause cold- and flu-like symptoms, upset stomach, joint ache, or headache.