DOSAGE AND ADMINISTRATION
There is no fixed dosage regimen for the management of diabetes mellitus with tolbutamide tablets or any other hypoglycemic agent. In addition to the usual monitoring of urinary glucose, the patient's blood glucose must also be monitored periodically to determine the minimum effective dose for the patient; to detect primary failure, i.e., inadequate lowering of blood glucose at the maximum recommended dose of medication; and to detect secondary failure, i.e., loss of an adequate blood glucose lowering response after an initial period of effectiveness. Glycosylated hemoglobin levels may also be of value in monitoring the patient's response to therapy.
Short-term administration of tolbutamide tablets may be sufficient during periods of transient loss of control in patients usually controlled well on diet.
Usual Starting Dose
The usual starting dose is 1 to 2 grams daily. This may be increased or decreased, depending on individual patient response. Failure to follow an appropriate dosage regimen may precipitate hypoglycemia. Patients who do not adhere to their prescribed dietary regimens are more prone to exhibit unsatisfactory response to drug therapy.
Transfer from Other Hypoglycemic Therapy
Patients Receiving Other Antidiabetic Therapy
Transfer of patients from other oral antidiabetes regimens to tolbutamide tablets should be done conservatively. When transferring patients from oral hypoglycemic agents other than chlorpropamide to tolbutamide, no transition period and no initial or priming doses are necessary. When transferring patients from chlorpropamide, however, particular care should be exercised during the first 2 weeks because of the prolonged retention of chlorpropamide, in the body and the possibility that subsequent overlapping drug effects might provoke hypoglycemia.
Patients Receiving Insulin
Patients requiring 20 units or less of insulin daily may be placed directly on tolbutamide tablets and insulin abruptly discontinued. Patients whose insulin requirement is between 20 and 40 units daily may be started on therapy with tolbutamide tablets with a concurrent 30% to 50% reduction in insulin dose, with further daily reduction of the insulin when response to tolbutamide tablets is observed. In patients requiring more than 40 units of insulin daily, therapy with tolbutamide tablets may be initiated in conjunction with a 20% reduction in insulin dose the first day, with further careful reduction of insulin as response is observed. Occasionally, conversion to tolbutamide tablets in the hospital may be advisable in candidates who require more than 40 units of insulin daily. During this conversion period when both insulin and tolbutamide tablets are being used hypoglycemia may rarely occur. During insulin withdrawal, patients should test their urine for glucose and acetone at least 3 times daily and report results to their physician. The appearance of persistent acetonuria with glycosuria indicates that the patient is type I diabetic who requires insulin therapy.
Maximum Dose
Daily doses of greater than 3 grams are not recommended.
Usual Maintenance Dose
The maintenance dose is in the range of 0.25 to 3 grams daily. Maintenance doses above 2 grams are seldom required.
Dosage Interval
The total daily dose may be taken either in the morning or in divided doses through the day. While either schedule is usually effective, the divided dose system is preferred by some clinicians from the standpoint of digestive tolerance.
In elderly patients, debilitated or malnourished patients, and patients with impaired renal or hepatic function, the initial and maintenance dosing should be conservative to avoid hypoglycemic reactions (see PRECAUTIONS).
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