Older adults have an increased sensitivity to the sulfonylureas and may require a dosage reduction.
After the patient has been taking sulfonylureas for a period of time, a condition called secondary failure may occur. Secondary failure occurs when the sulfonylurea loses its effectiveness. When the nurse notes that a normally compliant patient has a gradual increase in blood sugar levels, secondary failure may be the cause. This increase in blood glucose levels can be caused by an increase in the severity of the diabetes or a decreased response to the drug. When secondary failure occurs, the health care provider may prescribe another sulfonylurea or add an oral antidiabetic drug such as metformin to the drug regimen. See the Summary Drug Table: Antidiabetic Drugs for additional drugs that can be used in combination with the sulfonylureas.
a-GLUCOSIDASE INHIBITORS. Acarbose and miglitol are given three times as day with the first bite of the meal because food increases absorption. Some patients begin therapy with a lower dose once daily to minimize gastrointestinal effects, such as abdominal discomfort, flatulence, and diarrhea. The dose is then gradually increased to three times daily. The nurse monitors the response to these drugs by periodic testing. Dosage adjustments are made at 4- to 16-week intervals based on 1-hour postprandial glucose levels.
BIGUANIDES. The nurse gives metformin two or three times a day with meals. If the patient has not experienced a response in 4 weeks using the maximum dose of metformin, the primary care giver may add an oral sulfonylurea while continuing metformin at the maximum dose. Glucophage XR (metformin extended release) is administered once daily with the evening meal.
MEGLITINIDES. The nurse usually gives repaglinide 15 minutes before meals but can give it immediately, or up to 30 minutes, before the meal. Nateglinide is taken up to 30 minutes before meals.
THIAZOLIDINEDIONES. The thiazolidinediones, piogli-tazone and rosiglitazone, are given with or without meals. If the dose is missed at the usual meal, the drug is taken at the next meal. If the dose is missed on one day, do not double the dose the following day. If the drug is taken, do not delay the meal. Delay of a meal for as little as lh hour can cause hypoglycemia.
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