Tolinase - Pharmacia and Upjohn Company

Tolazamide appears to lower the blood glucose acutely by stimulating the release of insulin from the pancreas, an effect dependent upon functioning beta cells in the pancreatic islets. The mechanism by which tolazamide lowers blood glucose during long-term administration has not been clearly established. With chronic administration in Type II diabetic patients, the blood glucose lowering effect persists despite a gradual decline in the insulin secretory response to the drug. Extrapancreatic effects may be involved in the mechanism of action of oral sulfonylurea hypoglycemic drugs.

Some patients who are initially responsive to oral hypoglycemic drugs, including TOLINASE Tablets, may become unresponsive or poorly responsive over time. Alternatively, TOLINASE Tablets may be effective in some patients who have become unresponsive to one or more other sulfonylurea drugs.

In addition to its blood glucose lowering actions, tolazamide produces a mild diuresis by enhancement of renal free water clearance.

Tolazamide is rapidly and well absorbed from the gastrointestinal tract. Peak serum concentrations occur at three to four hours following a single oral dose of the drug. The average biological half-life of the drug is seven hours. The drug does not continue to accumulate in the blood after the first four to six doses are administered. A steady or equilibrium state is reached during which the peak and nadir values do not change from day to day after the fourth to sixth doses.

Tolazamide is metabolized to five major metabolites ranging in hypoglycemic activity from 0–70%. They are excreted principally in the urine. Following a single oral dose of tritiated tolazamide, 85% of the dose was excreted in the urine and 7% in the feces over a five-day period. Most of the urinary excretion of the drug occurred within the first 24 hours post administration.

When normal fasting nondiabetic subjects are given a single 500 mg dose of tolazamide orally, a hypoglycemic effect can be noted within 20 minutes after ingestion with a peak hypoglycemic effect occurring in two to four hours. Following a single oral dose of 500 mg tolazamide, a statistically significant hypoglycemic effect was demonstrated in fasted nondiabetic subjects 20 hours after administration. With fasting diabetic patients, the peak hypoglycemic effect occurs at four to six hours. The duration of maximal hypoglycemic effect in fed diabetic patients is about ten hours, with the onset occurring at four to six hours and with the blood glucose levels beginning to rise at 14 to 16 hours. Single dose potency of tolazamide in normal subjects has been shown to be 6.7 times that of tolbutamide on a milligram basis. Clinical experience in diabetic patients has demonstrated tolazamide to be approximately five times more potent than tolbutamide on a milligram basis, and approximately equivalent in milligram potency to chlorpropamide.

Patients should be informed of the potential risks and advantages of TOLINASE and of alternative modes of therapy. They should also be informed about the importance of adherence to dietary instructions, of a regular exercise program, and of regular testing of urine and/or blood glucose.

The risks of hypoglycemia, its symptoms and treatment, and conditions that predispose to its development should be explained to patients and responsible family members. Primary and secondary failure should also be explained.

Blood and urine glucose should be monitored periodically. Measurement of glycosylated hemoglobin may be useful in some patients.

The hypoglycemic action of sulfonylureas may be potentiated by certain drugs including nonsteroidal anti-inflammatory agents and other drugs that are highly protein bound, salicylates, sulfonamides, chloramphenicol, probenecid, coumarins, monoamine oxidase inhibitors, and beta-adrenergic blocking agents. When such drugs are administered to a patient receiving TOLINASE, the patient should be closely observed for hypoglycemia. When such drugs are withdrawn from a patient receiving TOLINASE, the patient should be observed closely for loss of control.

Certain drugs tend to produce hyperglycemia and may lead to loss of control. These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. When such drugs are administered to a patient receiving TOLINASE, the patient should be closely observed for loss of control. When such drugs are withdrawn from a patient receiving TOLINASE, the patient should be observed closely for hypoglycemia.

A potential interaction between oral miconazole and oral hypoglycemic agents leading to severe hypoglycemia has been reported. Whether this interaction also occurs with the intravenous, topical or vaginal preparations of miconazole is not known.

In a bioassay for carcinogenicity, rats and mice of both sexes were treated with tolazamide for 103 weeks at low and high doses. No evidence of carcinogenicity was found.

Although it is not known whether tolazamide is excreted in human milk, some sulfonylurea drugs are known to be excreted in human milk. Because the potential for hypoglycemia in nursing infants may exist, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. If the drug is discontinued and if diet alone is inadequate for controlling blood glucose, insulin therapy should be considered.

Safety and effectiveness in children have not been established.

Elderly patients are particularly susceptible to the hypoglycemic action of glucose lowering drugs. Hypoglycemia may be difficult to recognize in the elderly (see PRECAUTIONS). The initial and maintenance dosing should be conservative to avoid hypoglycemic reactions (see DOSAGE AND ADMINISTRATION).

Elderly patients are prone to develop renal insufficiency,which may put them at risk of hypoglycemia. Dose selection should include assessment of renal function.

See PRECAUTIONS and OVERDOSAGE sections.

Cholestatic jaundice may occur rarely; TOLINASE Tablets should be discontinued if this occurs. Gastrointestinal disturbances, eg, nausea, epigastric fullness, and heartburn, are the most common reactions and occurred in 1% of patients treated during clinical trials. They tend to be dose-related and may disappear when dosage is reduced.

Allergic skin reactions, eg, pruritus, erythema, urticaria, and morbilliform or maculopapular eruptions, occurred in 0.4% of patients treated during clinical trials. These may be transient and may disappear despite continued use of TOLINASE; if skin reactions persist, the drug should be discontinued.

Porphyria cutanea tarda and photosensitivity reactions have been reported with sulfonylureas.

Leukopenia, agranulocytosis, thrombocytopenia, hemolytic anemia, aplastic anemia, and pancytopenia have been reported with sulfonylureas.

Hepatic porphyria and disulfiram-like reactions have been reported with sulfonylureas; however, disulfiram-like reactions with TOLINASE have been reported very rarely.

Cases of hyponatremia have been reported with tolazamide and all other sulfonylureas, most often in patients who are on other medications or have medical conditions known to cause hyponatremia or increase release of antidiuretic hormone. The syndrome of inappropriate antidiuretic hormone (SIADH) secretion has been reported with certain other sulfonylureas, and it has been suggested that these sulfonylureas may augment the peripheral (antidiuretic) action of ADH and/or increase release of ADH.

Weakness, fatigue, dizziness, vertigo, malaise and headache were reported infrequently in patients treated during clinical trials. The relationship to therapy with TOLINASE is difficult to assess.

The usual starting dose of TOLINASE Tablets for the mild to moderately severe Type II diabetic patient is 100–250 mg daily administered with breakfast or the first main meal. Generally, if the fasting blood glucose is less than 200 mg/dl, the starting dose is 100 mg/day as a single daily dose. If the fasting blood glucose value is greater than 200 mg/dl, the starting dose is 250 mg/day as a single dose. If the patient is malnourished, underweight, elderly, or not eating properly, the initial therapy should be 100 mg once a day. Failure to follow an appropriate dosage regimen may precipitate hypoglycemia. Patients who do not adhere to their prescribed dietary regimen are more prone to exhibit unsatisfactory response to drug therapy.

Daily doses of greater than 1000 mg are not recommended. Patients will generally have no further response to doses larger than this.

The usual maintenance dose is in the range of 100–1000 mg/day with the average maintenance dose being 250–500 mg/day. Following initiation of therapy, dosage adjustment is made in increments of 100 mg to 250 mg at weekly intervals based on the patient's blood glucose response.

Once a day therapy is usually satisfactory. Doses up to 500 mg/day should be given as a single dose in the morning. 500 mg once daily is as effective as 250 mg twice daily. When a dose of more than 500 mg/day is required, the dose may be divided and given twice daily.

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 section).