There is no current evidence that says calcium channel blockers, including verapamil, affect the absorption of calcium or contribute to osteoporosis.

One study from 1987 found that verapamil had no effect on the intestinal absorption of calcium. Another report from 1992 found that an investigational calcium channel blocker, nitrendipine, had no effect on calcium metabolism or on bone density. A two-year study of nifedipine from 1996 came to a similar conclusion. Standard warnings about side effects of verapamil do not mention osteoporosis or calcium absorption as a concern.

Calcium channel blockers prevent calcium from entering the cells that line the arteries. This helps the arteries to relax, which lowers blood pressure and improves blood flow through arteries that have been narrowed by atherosclerosis.

These drugs also block calcium from entering the heart's muscle cells. This helps relax the heart muscle and reduces the amount of work the heart must do.

Together, the effects on arteries and the heart help to relieve angina, the chest pain caused by the heart getting too little oxygen. In addition, some calcium channel blockers are prescribed to slow the heartbeat. This can be helpful in treating certain rapid heart rhythms.

Calcium channel blockers can be quite effective in treating migraines. It's thought that by relaxing blood vessels, these drugs break the cycle of blood vessel constriction and sudden dilation, which is thought to contribute to painful migraines.

Side effects of verapamil include:

• Allergic reactions, such as rash or facial swelling
• Lightheadedness
• Upset stomach
• Fatigue
• Constipation

For most people taking calcium channel blockers, the benefits outweigh the risks. And the risks do not include osteoporosis.