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Dear Dr. Roach: I have a stent, but also a knee replacement, for which I take four 500-mg capsules of amoxicillin each time I go to the dentist, including just for cleaning. This is per my surgeon’s orders. Do you have any info that would question the necessity of this?

M.W.

Dear M.W.: Bacteria can get into the bloodstream occasionally in healthy people. They often enter through the mouth, especially in people with poor oral hygiene or with inflammatory oral conditions, such as gingivitis (gums) or periodontitis (tooth lining). The reason to take antibiotics is to prevent the bacteria in the blood from getting into someplace they are likely to cause harm, such as prosthetic heart valves, joints or stents. For years, expert groups recommended taking antibiotics around the time of dental procedures.

The problem is that it’s not clear whether antibiotics help prevent infection, and it is clear that antibiotics have the potential to cause harm, although the risk of serious problems with a single dose of amoxicillin is pretty small. No study has ever shown a reduction in the rate of serious infections from using antibiotics before a dental procedure. Further, bacteria are just about as likely to get into the bloodstream after brushing (or even after a bowel movement). For this reason, antibiotics to be taken before dental procedures are reserved for people at the highest risk, those in whom an infection would be extremely dangerous. This includes people with artificial materials in the bloodstream, such as prosthetic heart valves, or with repaired congenital heart disease. People with any history of infection of the heart valves are at high risk and should receive antibiotics.

For people like you, with orthopedic hardware, infection after a dental procedure is rare. A joint statement by the American Dental Association and the American Academy of Orthopedic Surgeons instructed: “In general, for patients with prosthetic joint implants, prophylactic antibiotics are not recommended prior to dental procedures to prevent prosthetic joint infection.” However, any given person may have underlying surgical or medical issues that may supersede these general recommendations.

What remains important is good oral hygiene and promptly treating any dental infections.

Dear Dr. Roach: Does taking Norvasc or any calcium channel blocker reduce or destroy the calcium in the bones, eventually causing osteoporosis?

E.G.

Dear E.G.: No. Calcium channel blockers, like amlodipine (Norvasc), work on cells in the heart and blood vessels, controlling the flow of calcium into the cell. Calcium in the cell is one of the regulators of smooth muscle cells, and for Norvasc in particular, that means its major effect is on blood vessels, causing them to open up and reduce blood pressure, and thus the amount of work the heart needs to do.

Calcium in bone is used structurally, where it combines with other ions to form hydroxyapatite, the mineral that keeps bones hard and strong. The mechanism for calcium entry into bone cells is very different. Calcium channel blockers do not affect mineralization of the bone, nor do they increase the risk for osteoporosis.

One group found that people on calcium channel blockers may have a slightly higher risk of fractures; however, that was thought to be due to an increased number of falls, especially in the elderly. Physicians need to take care not to use too much medication, especially ones that dilate blood vessels, as they can increase risk of dizziness and falls.

Email questions to ToYourGoodHealth@med.cornell.edu.

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