How does this medication work? What will it do for me?

Tolbutamide belongs to the class of medications called oral hypoglycemics. It is used for the control of blood glucose (sugar) for people with type 2 diabetes. It is used when diet, exercise, and weight reduction have not been found to control blood glucose well enough on their own.

Tolbutamide works by increasing the amount of insulin (a hormone produced by the pancreas that allows sugar to enter into cells where it is needed for energy) released by the pancreas and by helping the body to use insulin more efficiently.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each round, white, biconvex, scored tablet marked "APO" over "TOL" on one side contains 500 mg of tolbutamide. Nonmedicinal ingredients: information not available.

How should I use this medication?

The recommended adult dose of tolbutamide ranges from 500 mg to 3,000 mg per day, either as a single dose or in divided doses, depending on the need according to blood glucose tests and as prescribed by your doctor. The tablets should be taken with or before food.

It is very important to monitor blood sugar levels closely, especially when increasing and decreasing doses of medication or when exercise levels or weight changes occur. Your doctor or diabetes educator will instruct you on the best use of a glucose monitor.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Low blood sugar (hypoglycemia) is an important concern if too much of this medication is taken for your circumstances. Ask your doctor or diabetes educator what you should do when you are not going to be eating for a long period of time or when you are going to be exercising more than usual.

Store this medication at room temperature, protect it from moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Tolbutamide should not be taken by anyone who:

  • is allergic to tolbutamide or to any of the ingredients of the medication
  • is breast-feeding
  • is in a state of ketoacidosis (high ketones in urine)
  • is pregnant
  • is undergoing surgery or has suffered from recent severe trauma
  • has a serious infection
  • has severely reduced kidney and liver function
  • has thyrotoxicosis (severe overactive thyroid brought on by stress or infection)
  • has type 1 diabetes (they should always be using insulin)

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • changes in taste sensation
  • constipation
  • diarrhea
  • dizziness
  • heartburn
  • increased amount of urine or more frequent urination
  • increased or decreased appetite
  • passing gas
  • stomach pain, fullness, or discomfort
  • vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • chest pain
  • chills
  • coughing up of blood
  • dark urine
  • fever
  • fluid-filled skin blisters
  • general feeling of illness
  • increased amounts of sputum (phlegm)
  • increased sweating
  • light-coloured stools
  • low blood sugar, including:
    • anxious feelings
    • behavioural changes similar to being drunk
    • blurred vision
    • cold sweats
    • confusion
    • cool, pale skin
    • difficulty concentrating
    • drowsiness
    • excessive hunger
    • fast heartbeat
    • headache
    • nausea
    • nervousness
    • nightmares
    • restless sleep
    • shakiness
    • slurred speech
    • unusual tiredness or weakness
  • pale skin
  • peeling of skin
  • sensitivity to the sun
  • shortness of breath
  • skin redness, itching, or rash
  • sore throat
  • thinning of the skin
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight gain
  • yellow eyes or skin

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • convulsions (seizures)
  • unconsciousness

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Blood sugar control: Over a period of time, people may become progressively less responsive to a particular treatment for diabetes because of a worsening of their diabetes. If tolbutamide fails to lower blood glucose to target levels, the medication should be stopped and replaced, or another medication added to it. Loss of blood sugar control may occur during illness or stressful situations such as trauma or surgery. Under these conditions, your doctor may consider stopping the medication and prescribing insulin until the situation improves.

Diabetes complications: Although this medication may delay the development of complications, tolbutamide has not been shown to prevent the development of complications of diabetes. Tolbutamide must be used in addition to a proper dietary regimen and not as a substitute for diet.

Drowsiness/reduced alertness: Until your blood sugar is under control, or when changing doses of medication or when the tablets have not been taken regularly, use caution when driving or operating dangerous machinery, as alertness and reaction time may be reduced.

Low blood sugar: As with other sulfonylurea medications like tolbutamide, symptoms of hypoglycemia (low blood sugar) including dizziness, lack of energy, drowsiness, headache, and sweating have been observed with use of this medication. Weakness, nervousness, shakiness, and numbness or tingling have also been reported. Severe hypoglycemia can result from taking any of the sulfonylurea medications. Seniors, those with reduced kidney or liver function, and those who are fragile or malnourished are more likely to experience low blood sugar with these medications.

Low blood sugar is more likely to occur when food intake is inadequate or after strenuous or prolonged physical exercise. Blood glucose should be monitored regularly and emergency glucose (and glucagon kit) should be kept available in case the need arises to increase blood sugar levels.

Reaction with alcohol: Unpleasant reactions to alcohol (flushing, sensation of warmth, giddiness, nausea, and occasionally racing heart rate) may occur for people taking tolbutamide. This reaction can be prevented by avoiding the use of alcohol.

Pregnancy: Tolbutamide should not be taken by pregnant women (insulin should be used to control blood sugar). If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Tolbutamide passes into breast milk and should not be taken by breast-feeding women. If you are a breast-feeding mother and are taking tolbutamide, it may affect your baby.

What other drugs could interact with this medication?

There may be an interaction between tolbutamide and any of the following:

  • acetazolamide
  • alcohol
  • anabolic steroids
  • androgens (e.g., testosterone)
  • angiotensin converting enzyme (ACE) inhibitors (e.g., enalapril, ramipril)
  • aprepitant
  • "azole" antifungals (e.g., fluconazole, ketoconazole)
  • beta-blockers (e.g., nadolol, propanolol)
  • birth control pills
  • calcium channel blockers (e.g., diltiazem, verapamil)
  • chloramphenicol
  • cimetidine
  • clarithromycin
  • corticosteroids (e.g., prednisone)
  • cyclophosphamide
  • cyclosporine
  • diazoxide
  • disopyramide
  • diuretics (e.g., hydrochlorothiazide, chlorthalidone, indapamide)
  • estrogens
  • fibrates (e.g., clofibrate, fenofibrate)
  • fluoxetine
  • guanethidine
  • ifosfamide
  • leflunomide
  • luteinizing hormone-releasing hormone analogs (e.g., buserelin, goserelin, leuprolide)
  • monoamine oxidase (MAO) inhibitors (e.g., phenelzine, tranylpromine)
  • nicotinic acid (niacin)
  • nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen, naproxen)
  • other antidiabetes medications
  • pegvisomant
  • phenothiazines (e.g., chlorpromazine, thioridazine, prochlorperazine)
  • phenylbutazone
  • phenytoin
  • probenecid
  • quinolones (e.g., ciprofloxacin, ofloxacin)
  • ranitidine
  • rifampin
  • salicylates (e.g., ASA)
  • somatropin
  • suflinpyrazone
  • sulfonamides (e.g., sulfasalazine, sulfamethoxazole)
  • sympathomimetic amines (e.g., epinephrine)
  • tetracycline
  • thyroid hormone
  • warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.