Resources and information for parents of children with cancer . . . by parents of children with cancer.

Antibiotics

Children on chemotherapy take antibiotics two to three days each week to prevent pneumocystis pneumonia (PCP). They will probably continue to take the antibiotics six months to a year following cessation of chemotherapy. The prescription of preventative or prophylactic antibiotics is somewhat at the discretion of the oncologist. If the risks outweigh the benefits, the child will not be on the antibiotics. Also, some parts of the country are less prone to PCP, a fact which may weigh in the doctor's decision.

Children that are HIV positive or have AIDS also take these same antibiotics.

The antibiotic of choice for PCP prevention is a combination drug consisting of sulfamethoxazole and trimethoprim:

It is sold under the brand name "Bactrim" or "Septra", among others. Read your child's prescription label carefully and it should list the two above ingredients. It is supplied as a tablet or suspension to be administered orally as a preventative (if your child were to develop PCP, Bactrim would be administered IV). Here are the doses:

Children swear that different brand names and/or generic formulations of this antibiotic taste different, either in pill or suspension form. My teen hates even the pills; for awhile I had to crush them up and put them in gel caps. I can just imagine how awful the suspension might taste. (Try it yourself!) If you are having problems getting your child to take this oral medication, you might try a different brand or pharmacy. The antibiotic is cheap, so it's not a lot out of your pocket if you have to look around, even if you have to go outside your health insurance coverage. These antibiotics are very important, and have to be taken for several years, so it's worth taking the time to work out an arrangement that your child likes. Give them some power to try different ones and make their own choice.

Note: You can buy these tablets in a very large size, over 100, so you don't have to keep going back for refills.

Antibiotics should be taken with plenty of water or other fluids.

Pneumocystis Carinii Pneumonia (PCP)

Bactrim is essentially 100% effective in preventing PCP in children on chemotherapy. PCP is aggressive, fast-moving, and sometimes hard to detect. Any pneumonia is a real concern for children on chemo, but PCP is particularly nasty pneumonia. It is caused by pneumocystis carinii, thought to be a fungus which is usually dormant in the hosts lung. PCP presents as:

Your child's oncologist will likely do a check for PCP in the event of the above symptoms. PCP is diagnosed by checking lung fluid for the pneumocystis carinii. PCP progresses very quickly and must be treated with immediate and aggressive treatment. It's treated by IV administration of Bactrim (or alternative, see below). According to the Merck Manual:

"the overall mortality with treatment is 10 to 30%"

This is pretty scary, for a disease that can be entirely prevented by taking pills a couple days a week.

It is probably not a concern, but the literature states that PCP can be transmitted from patient to patient. I can't see this as a problem, unless your child is sharing a hospital room with a child who has PCP.

Adverse Reactions

Sulfamethoxazole inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA, yes, the sunscreen compound). Trimethoprim blocks the production of tetrahydrofolic acid from dihydrofolic acid by binding to and inhibiting the required enzyme. Combined, the two antibiotics block two consecutive steps in the biosynthesis of nucleic acids and proteins essential to many bacteria. This data was presented for bacteria, I am assuming that it can be extrapolated to the possibly fungal pneumcystis carinii. (This information is according to Danbury Pharmaceutical, the manufacturer who printed the slip included with Bactrim.)

The most common adverse reactions are: (again, from the slip of paper provided by the manufacturer with the prescription)

Bactrim can cause adverse reactions in some children, including severe allergic, hematological, respiratory, and neurological problems. These reactions are rare, but they can and do occur. Realistically, with all the chemotherapy the kids are taking and with their own nasty side effects, it can be difficult to attribute problems to the antibiotic. Still, be aware.

Children undergoing chemotherapy are particularly susceptible to neutropenia due to Bactrim. Listening to online chat for several months, more than one child was taken off Bactrim in order to allow the ANC -- the "counts" -- to come back up. Usually, Pentamidine or Dapsone is substituted during the suspension from Bactrim.

I included the biochemical actions of sulfamethazole and trimethoprim above for a reason (other than my own chemist nature). Note that these antibiotics work on the same pathway as does methotrexate, a chemotherapy agent common in the treatment of many childhood cancers, especially ALL. According to the manufacturer, the antibiotic:

Therefore, your child should not be taking Bactrim on the same say as he or she receives a dose of methotrexate (MT). The serum concentrations of the antibiotic peak 1-4 hours after oral administration, so it can likely be given the day before. Always ask your doctor if they tell you otherwise.

Alternatives to Bactrim

A significant number of children need to discontinue Bactrim because of a drop in blood counts attributed to this antibiotic. Or, the child has an allergic reaction to the Bactrim. Substitutes include:

In patients with HIV infection, Pentamidine is clearly not as good as Bactrim at preventing PCP. The general consensus that I found from reading Web sources is that Bactrim is always the first choice, and Pentamidine and Dapsone are very good alternatives, but not as well-thought of as Bactrim for preventing and treating PCP, and perhaps have unwanted side-effects. Still, things change with time, so keep an eye on the AIDS-related Web pages for new alternative preventative treatments for PCP.

Web References

Literature References

General Disclaimer

These pages are intended for informational purposes only and are not intended to render medical advice. The information provided on Ped Onc Resource Center should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you suspect your child has a health problem, you should consult your health care provider.

contact webmaster/ped-onc home/last updated 7/05