TOLAZAMIDE

TOLAZAMIDE- tolazamide tablet
Mutual Pharmaceutical Company, Inc

Rx only

DESCRIPTION

Tolazamide tablets contain tolazamide, an oral blood glucose lowering drug of the sulfonylurea class. Tolazamide is a white or creamy-white powder with a melting point of 165° to 173° C. The solubility of tolazamide at pH 6.0 (mean urinary pH) is 27.8 mg per 100 mL.

The chemical names for tolazamide are (1) Benzenesulfonamide, N -[[(hexahydro-1H -azepin-1-yl) amino] carbonyl]-4-methyl-; (2) 1-(Hexahydro-1H -azepin-1-yl)-3-(p -tolylsulfonyl) urea and its molecular weight is 311.40. The structural formula is represented below:

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Tolazamide tablets for oral administration are available as scored, white tablets containing 100 mg, 250 mg or 500 mg tolazamide.

Inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, docusate sodium, magnesium stearate, microcrystalline cellulose, plasdone, sodium benzoate, stearic acid.

CLINICAL PHARMACOLOGY

Actions

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 tolazamide, may become unresponsive or poorly responsive over time. Alternatively, tolazamide 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.

Pharmacokinetics

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 l4 to16 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.

INDICATIONS AND USAGE

Tolazamide tablets are indicated as an adjunct to diet to lower the blood glucose in patients with noninsulin-dependent diabetes mellitus (Type II) whose hyperglycemia cannot be satisfactorily controlled by diet alone.

In initiating treatment for noninsulin-dependent diabetes, diet should be emphasized as the primary form of treatment. Caloric restriction and weight loss are essential in the obese diabetic patient. Proper dietary management alone may be effective in controlling the blood glucose and symptoms of hyperglycemia. The importance of regular physical activity should also be stressed and cardiovascular risk factors should be identified and corrective measures taken where possible.

If this treatment program fails to reduce symptoms and/or blood glucose, the use of an oral sulfonylurea or insulin should be considered. Use of tolazamide must be viewed by both the physician and patient as a treatment in addition to diet and not as a substitute for diet or as a convenient mechanism for avoiding dietary restraint. Furthermore, loss of blood glucose control on diet alone may be transient thus requiring only short-term administration of tolazamide.

During maintenance programs, tolazamide should be discontinued if satisfactory lowering of blood glucose is no longer achieved. Judgments should be based on regular clinical and laboratory evaluations.

In considering the use of tolazamide in asymptomatic patients, it should be recognized that controlling the blood glucose in noninsulin-dependent diabetes has not been definitely established to be effective in preventing the long-term cardiovascular or neural complications of diabetes.

CONTRAINDICATIONS

Tolazamide tablets are contraindicated in patients with: 1) known hypersensitivity or allergy to tolazamide; 2) diabetic ketoacidosis, with or without coma. This condition should be treated with insulin; 3) Type I diabetes, as sole therapy.

SPECIAL WARNING ON INCREASED RISK OF CARDIOVASCULAR MORTALITY

The administration of oral hypoglycemic drugs has been reported to be associated with increased cardiovascular mortality as compared to treatment with diet alone or diet plus insulin. This warning is based on the study conducted by the University Group Diabetes Program (UGDP), a long-term prospective clinical trial designed to evaluate the effectiveness of glucose-lowering drugs in preventing or delaying vascular complications in patients with noninsulin-dependent diabetes. The study involved 823 patients who were randomly assigned to one of four treatment groups (DIABETES, 19 (supp.2):747-830, 1970.)

UGDP reported that patients treated for five to eight years with diet plus a fixed dose of tolbutamide (1.5 grams per day) had a rate of cardiovascular mortality approximately 2½ times that of patients with diet alone. A significant increase in total mortality was not observed, but the use of tolbutamide was discontinued based on the increase in cardiovascular mortality, thus limiting the opportunity for the study to show an increase in overall mortality. Despite controversy regarding the interpretation of these results, the findings of the UGDP study provide an adequate basis for this warning. The patient should be informed of the potential risks and advantages of tolazamide and of alternative modes of therapy.

Although only one drug in the sulfonylurea class (tolbutamide) was included in this study, it is prudent from a safety standpoint to consider that this warning may also apply to other oral hypoglycemic drugs in this class, in view of their close similarities in mode of action and chemical structure.

PRECAUTIONS

General

Hypoglycemia

All sulfonylurea drugs are capable of producing severe hypoglycemia. Proper patient selection and dosage and instructions are important to avoid hypoglycemic episodes. Renal or hepatic insufficiency may cause elevated blood levels of tolazamide and the latter may also diminish gluconeogenic capacity, both of which increase the risk of serious hypoglycemic reactions. Elderly, debilitated, or malnourished patients and those with adrenal or pituitary insufficiency are particularly susceptible to the hypoglycemic action of glucose lowering drugs. Hypoglycemia may be difficult to recognize in the elderly and in people who are taking beta-adrenergic blocking drugs. Hypoglycemia is more likely to occur when caloric intake is deficient, after severe or prolonged exercise, when alcohol is ingested, or when more than one glucose-lowering drug is used.

Loss of Control of Blood Glucose

When a patient stabilized on any diabetic regimen is exposed to stress such as fever, trauma, infection, or surgery, loss of control of blood glucose may occur. At such times it may be necessary to discontinue tolazamide and administer insulin.

The effectiveness of any hypoglycemic drug, including tolazamide, in lowering blood glucose to a desired level decreases in many patients over a period of time, which may be due to progression of the severity of the diabetes or to diminished responsiveness to the drug. This phenomenon is known as secondary failure to distinguish it from primary failure in which the drug is ineffective in an individual patient when first given. Adequate adjustment of dose and adherence to diet should be assessed before classifying a patient as a secondary failure.

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