Pediatricians left guessing at drug doses

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Pediatricians left guessing at drug doses

By Dr. McEvoy

Boston Globe*

March 31, 2008

http://www.boston.com/news/health/articles/2008/03/31/pediatricians_l

eft_guessing_at_drug_doses/

It was one of many bad days I had as an intern at a busy city

hospital: One of my fellow interns had tattled to our supervisor

that I had written a prescription for amoxicillin that was twice as

strong as it should have been.

more stories like thisIt was a rookie error - despite carefully

calculating the correct dose based on the child's weight after

consulting my trusty Harriet Lane Handbook, I had forgotten that

amoxicillin came in different strengths. And as it turns out, the

dose I had erroneously prescribed then would actually be the correct

dose for treating an ear infection today.

Welcome to the world of pediatric drug dosing, a moving target of

sometimes unknown or hard-to-find recommendations that can change

frequently. Sometimes the lack of information puts doctors in the

position of simply making an educated guess.

For years parents would come into my exam room anxiously clutching

over-the-counter medications such as Triaminic with queries about

proper dosing: " Dr. McEvoy, it says for children under 2 years, to

consult their doctor. " Many times I would slink off to another room

and consult the Physician Desk Reference, the Bible for all drug

questions. There I would be met by the same show stopper - " consult

your physician for ages under 2 " or " studies have not been completed

for children under 2, " or there would be a chart of dosages based on

weight. . . . for all children over the age of 3 months.

But what if a baby under 3 months needed a medication? How should I

know what the dose should be?

Now it's clear that many of the pediatric cold formulas are not

effective - and worse, may be harmful. They weren't, it seems,

tested on children under 6 years old.

Although we'd all like to avoid medicating children entirely, there

are times when pediatricians really do need to know the proper, safe

dose of a drug to give a child. For example, infants often get a

condition known as thrush, which is characterized by a thick, white

coating on the tongue and inside lining of the mouth, and can

interfere with feeding. It is caused by yeast, Candida Albicans, and

it used to respond to a drug called Nystatin, but it often doesn't

anymore.

Many pediatricians have turned to Diflucan, another anti-fungal

agent. However, using Diflucan to treat fungus in infants is

considered an " off label " use, meaning studies have not been done

for this condition. And finding the proper dose to use sets

physicians on a frustrating search. Many times, the discovery of

such " off label " uses as well as the proper dose comes by

happenstance - perhaps you hear a certain speaker at an educational

seminar or just happen to read an article; maybe one of your

colleagues shares a " trade secret. " But, of course, by using such a

drug for " off-label " use, the prescribing doctor assumes more

responsibility.

There are many reasons why drugs are still not adequately tested in

children. It is not hard to imagine the ethical issues involved with

drug experiments, but, as others have noted, the absence of such

studies keeps helpful treatments from sick children.

more stories like thisEnrolling a child in a drug study requires

consent - that of the parents and that of the child. The American

Academy of Pediatrics argues that a child of seven is cognitively

able to understand risk. What about all the children under seven?

And is a sick child of seven really able to weigh the pros and cons

of a clinical trial?

Additionally, in order to be in a study, a child must be suffering

from the condition that the drug is supposed to treat. And if the

child is sick, how can one withhold the treatment and knowingly give

the child a placebo?

Doses for children are usually based on weight but other factors

come into play as well. Infants may require significantly less of a

medication than adults, not only because of their weight, but also

because their liver and kidneys are not mature. Older children

sometimes metabolize drugs at a faster rate than adults, so they may

need more of a particular drug. In other words, children are not

just little adults.

While dosing for serious conditions such as heart disease is

explicit - because the medications are so dangerous, careful studies

have been done and dosing is specific. But for common prescriptions

such as antibiotics it's a different story. Amoxicillin treatment

for an ear infection, for instance, might require a dose of anywhere

from 1 teaspoon twice-a-day for five days to 2 teaspoons three times-

a-day for 10 days. The guidelines are intentionally broad to

encourage doctors to take into account the patient's age, the nature

and severity of the infection, and the likelihood of resistance to

certain strains of bacteria.

In other words, prescribing drugs to children is very confusing. The

good news is we now know some ear infections don't need treatment at

all.

And maybe that's the moral for parents and pediatricians alike:

Often, doing nothing is the best dose of all.