What is Chemoprophylaxis?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 11 September 2019
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A student at a school finds out she has been directly exposed to bacterial meningitis and appropriately sees a doctor for advice. The doctor’s response is to prescribe antibiotics, even though the student is not sick. The purpose of the antibiotics are to prevent potential development of meningitis, and use of medications for prevention is generally called chemoprophylaxis or sometimes simply prophylaxis. Such prevention can be an important part of medicine and there are many different circumstances in which drug based preventatives or chemoprophylaxis become valuable treatment.

One of the most common forms of chemoprophylaxis is called bacterial endocarditis (BE) prophylaxis. People who have had heart surgery, and especially who have any artificial valves or replacement of valves in the heart are at greater risk for developing a bacterial infection in the heart especially when they undergo any type of dental work. Even a teeth cleaning is a risk in this respect because it’s easy for bacteria from the mouth to enter the body through tiny cuts in the lips or gums. To address this issue, chemoprophylaxis, again in the form of antibiotics, is used to prevent infection, and only one dose is needed about an hour prior to dental work as a preventative.


Another group of people at risk for constant infection are those who don't have a spleen. They may need to take daily antibiotics since chances of viral infection morphing into bacterial infection are much higher. This is especially the case for those people born without spleens. Older adults who lose a spleen might not require this form of chemoprophylaxis. Other people who might need daily antibiotic chemoprophylaxis include those with suppressed immune systems from diseases or conditions, and those who have chronic infections.

Medications other than antibiotics may be part of disease prevention and reduction. Chemoprophylactic use of tamoxifen has been widely studied because the medication has been shown to reduce breast cancer incidence. The drug may now be recommended to those women of a certain age who fall into high-risk groups for breast cancer. While this medication is not without its benefits, it does tend to illustrate some of the issues associated with prevention of illness via chemoprophylaxis.

Medications that may prevent disease can have side effects. When doctors consider prescribing chemoprophylactic therapy, they must weigh a number of things. These include side effects of treatment versus risk and severity of illness, and possibly cost of treatment against percentage of people who get ill without it. Patients also need to evaluate these things when long-term preventative drug therapy is advocated, and not all patients arrive at the same conclusions.

Treatment in advance of illness is clearly preventative medicine. Chemoprophylaxis is merely one avenue that may reduce illness risk. Yet it is often a good one, since some conditions are easier to prevent than to cure. The student with bacterial meningitis who doesn’t get treatment runs the risk of a very difficult and possibly life-threatening disease, though it should be noted that not all people avoid illness even with antibiotics. When doctors arrest the disease process and prevent that student or any other person from getting sick, they’ve accomplished something quite significant.



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