Drugs Increase Osteoporosis Risk

By Robert Shmerling, M.D.
Content provided by the Faculty of the Harvard Medical School

Drugs for two common conditions may increase the risk of fragile bones and fractures, new studies report. One study looked at the diabetes drugs pioglitazone and rosiglitazone. People who used one of these drugs for at least a year were more than twice as likely to break a bone. The fractures occurred with low impact, such as a simple fall. The other study included young women who took phenytoin, a drug for epilepsy. They lost bone density eight times as fast as other young women. Reuters Health reported on the diabetes drugs April 29. The study was in the Archives of Internal Medicine. HealthDay News wrote about the epilepsy drugs April 28. The study was in the journal Neurology.

What Is the Doctor's Reaction?

You may have heard a lot about osteoporosis. It's a condition in which the bones fracture more easily than they should. All bone is porous. This means that it contains tiny holes. But in someone with osteoporosis the bones are more porous (less dense) than normal.

You may also have heard a lot about drugs that treat osteoporosis. The drugs include alendronate (Fosamax), risedronate (Actonel) and ibandronate (Boniva). Television and print media ads for these drugs are hard to miss.

But have you ever heard of medications causing osteoporosis? The most common ones include:

  • Steroids (or corticosteroids), such as prednisone

  • Heparin, a blood thinner

  • Thyroid hormone replacement (when the dose is too high)

  • Anti-seizure medicines (drugs for epilepsy)

Two new studies provide important and useful information about drug-induced osteoporosis.

The first study links an older anti-seizure medicine, phenytoin (Dilantin), to bone loss. Researchers in New York City enrolled 93 women between the ages of 18 and 40. Each of them took one of four anti-seizure medicines.

Bone mineral density (BMD) tests were done at the start of treatment and a year later. Women taking phenytoin had a significant (2.6%) drop in bone density in the hip. If this amount of bone loss continued year after year, it could put these women at major risk of fracture.

Other anti-seizure drugs were not associated with bone loss.

Phenytoin has long been included in the list of drugs that may contribute to osteoporosis. However, this is one of the first studies to measure its effect on bone density in young women.

The other study links two popular diabetes drugs to an increased risk of bone fracture. Researchers in Switzerland compared 1,020 people who had a fracture with more than 3,700 otherwise similar people who did not have a fracture. Those with a fracture were much more likely to be taking pioglitazone (Actos) or rosiglitazone (Avandia).

Other factors also increase the risk of osteoporosis. Researchers adjusted their numbers to account for these factors. But people who took pioglitazone or rosiglitazone still had a two to three times higher risk of hip or other fracture than those not taking the drugs. The longer people took these drugs, the higher their risk of fracture.

These two studies are important reminders that a medicine can have long-term side effects. These effects are only appreciated well after the drug is approved.

However, I don't think people should stop taking these drugs. The benefits may outweigh the risk of bone loss. Since we know that these drugs may contribute to osteoporosis, we may be able to take measures to prevent it.

These new findings add to those of another recent study. This study linked a type of diuretic (water pill) to bone loss in the hip. "Loop diuretics" (including the commonly prescribed drug furosemide, or Lasix) are used to treat swelling and high blood pressure. Earlier this month, researchers reported that loop diuretics contribute to bone loss because they encourage loss of calcium in the urine.

What Changes Can I Make Now?

You can reduce your risk of osteoporosis. Among the most important ways are:

  • Exercise regularly. Weight-bearing activities (such as walking or tennis) are particularly important to increase bone strength.

  • Choose foods that are rich in calcium and vitamin D. Dairy products, salmon and fortified orange juice are good sources of calcium. Foods with high vitamin D content include salmon, mackerel, tuna and fortified dairy products.

  • Consider taking supplements. Calcium (1,000 milligrams per day) and vitamin D (400 to 800 units/day) are easy to find and don't cost much. You can buy these pills without a prescription. Your doctor can help you decide whether taking them is a good idea.

  • Moderate your alcohol intake. A reasonable limit is no more than two drinks per day for men and no more than one drink daily for women.

  • Get your bone mineral density checked. The National Osteoporosis Foundation recommends testing for all women over age 64 and for men over age 69. Testing is recommended earlier if you have an increased risk of osteoporosis or if you have had a fracture from a low-impact cause, such as a simple fall. You can use your risk factors to calculate your risk of having a fracture due to osteoporosis.

  • If your bone mineral density is low, ask your doctor about reversible causes. These can include thyroid disease, lack of vitamin D or low testosterone. Consider osteoporosis medicines to halt or reverse bone loss.

  • Review the medicines you take with your doctor or pharmacist. This is especially important if you already have osteoporosis. It's also important if you have osteopenia. This means that you have low bone density, but not as severe as osteoporosis. If you take a drug linked to bone loss, talk to your doctor about other treatment options.

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Women ages 19 to 50 need at least 1,000 milligrams of calcium every day. Younger women and women older than 50 need even more.