Metformin

Brand names

• Alti-Metformin
• Apo-Metformin
• Dom-Metformin
• Gen-Metformin
• Glucophage
• Glycon
• Novo-Metformin
• Nu-Metformin
• PMS-Metformin
• Rhoxal-Metformin
• Riva-Metformin

Usage

Used to lower abnormally high blood glucose (sugar) levels in patients with noninsulin-dependent (type 2) diabetes whose blood sugar levels cannot be adequately controlled by diet or exercise alone. The medicament may be used alone or in conjunction with sulfonylurea medicaments or insulin.

How it works

Metformin decreases the liver's production of glucose, inhibits the breakdown of fatty acids used to produce glucose, and increases the removal of glucose from muscle, the liver, and other body tissues where it is stored.

Side effects

Serious

In rare cases, metformin may lead to lactic acidosis, an abnormal and potentially life-threatening buildup of lactic acid in the blood. Symptoms include rapid, shallow breathing; unusual sleepiness or weakness; muscle pain; and abdominal distress. Metformin also occasionally causes abnormally low blood glucose levels (hypoglycemia); symptoms include blurred vision, cold sweats, confusion, anxiousness, rapid heartbeat, shakiness, and nausea. Seek medical assistance immediately.

Common

Diarrhea, nausea, vomiting, abdominal bloating, gas, diminished appetite. Usually such symptoms are mild and transient. Consult your doctor if the symptoms persist or increase in severity.

Less common

Unpleasant or metallic taste in mouth.

Possible interactions

Other medicaments:

Metformin may increase the effects of:

• insulin, in the sense that the lowering of blood sugar will be increased; this may be used to therapeutic advantage in some insulin-dependent diabetics.

Metformin taken concurrently with:



• ACE inhibitors may increase lowering of blood sugar to an undesirable extent.
• azole antifungals may increase lowering of blood sugar to an undesirable extent.
• beta blockers may slow recovery from any hypoglycemia that occurs and can also block symptoms of low blood sugar.
• cationic medicaments (cotrimoxazole, quinidine, quinine and others) may increase risk of lactic acidosis.
• contrast media for certain X-ray studies may increase risk of lactic acidosis. Metformin should not be combined with these agents. Some clinicians substitute a different agent to control blood sugar, stop the metformin 48 hours before the X ray and then stop the substituted agent and restart metformin once kidney function is tested and found to be normal.
• cotrimoxazole (Bactrim, others) may increase risk of lactic acidosis.
• digoxin (Lanoxin, others) may pose a problem because it is a cationic medicament and may lead to excess metformin levels.
• itraconazole (Sporanox) or other azole antifungal agents can result in severe lowering of the blood sugar.
• procainamide (Pronestyl) may lead to toxicity.
• quinidine (Quinaglute) may lead to toxicity.
• thyroid hormones can result in blunting of metformin's therapeutic effect.

The following medicaments may increase the effects of metformin:



• cimetidine (Tagamet)-may result in toxicity.
• morphine (various)-may lead to toxicity.
• nifedipine (Adalat)-may lead to toxicity.
• oral antidiabetic medicaments-this effect may be used to therapeutic advantage.
• ranitidine (Zantac)-may lead to toxicity.
• trimethoprim (Septra)-may lead to toxicity.
• vancomycin (Vancoled)-may lead to toxicity.

Herbal medicines or minerals:

Using chromium may change the way your body is able to use sugar. Some health food stores advocate vanadium as mimicking the actions of insulin, but possible toxicity and need for rigorous studies presently preclude recommending it. DHEA may change sensitivity to insulin or insulin resistance. Hawthorn, ginger, garlic, ginseng and licorice, nettle and yohimbe may change blood sugar. Since this may require adjustment of hypoglycemic medicine dosing, talk to your doctor before combing any of these herbal medicines with acarbose. Echinacea pupurea (injectable) and blonde psyllium seed or husk should not be taken by people living with diabetes. Caution: Like this medicine, St. John's wort may increase sensitivity to the sun.

Alcohol:

Alcohol worsens the effect of metformin on lactate. Avoid alcohol in excessive amounts.

Marijuana smoking:

May worsen dizziness.

Exposure to sun:

Some medicines that are similar in chemical structure can cause increased sensitivity to the sun.

Heavy exercise or exertion:

Heavy exercise will tend to use up sugar faster than usual. This medicament will have an effect on lowering the blood sugar. Be alert to the symptoms of low blood sugar.

Occurrence of unrelated illness:

Infections or other illness may still require use of insulin to achieve acceptable blood sugar control.