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gel formulations
Posted by: Doctor Kristopher Hartwig (IP Logged)
Date: October 27, 2003 12:07PM

We use topical thorazine occasionally, as well as
several other drugs (notably for nausea/vomiting), via
PLO gel (discussed here within the past year or so).
As medical director I am cautious about showing
enthusiasm for this route as it seems doomed to the
"alternative" realm of medical thinking. This is
unfortunate, because the gels are a great tool in the
home setting. Patients obviously prefer it to rectal
suppositories or subq apparati. "Evidence" of
efficacy is tough just because it is a home tool, the
inpatient units
clearly preferring subq or iv access. But we (mostly)
titrate our drugs to effect, not to a particular dose,
so it may not matter how much (or how little)
thorazine is absorbed as long as we "see" the desired
effect.. It's easy to be convinced of gel efficacy
when intractable n and v returns only with cessation
of the gel, and then is controlled with reapplication.
Terminal delirium/agitation is tougher, as we seldom
get a chance to readminister a drug. But unless a
significant cohort of experienced nurses are wrong,
and we
trust their evaluations in so many aspects of our
care, there is a similar apparent efficacy with the
gel vs the rectal route.
I don't doubt that drug is absorbed, but make few
presumptions as to amount. Thus we seldom if ever use
opiates by PLO gel as the conversions are too shaky.
And if a n/v case controlled with a gel "soup" of
haldol/benadry/ativan/reglan needs help with delirium,
we add haldol orally or subq.
As to data, the articles I've seen are from pharmacy
journals and are not clinically convincing. So we're
stuck with more anecdotes!
Kristopher Hartwig Hospice Chuatauqua County

Re: gel formulations
Posted by: Doctor Greg Holmquist (IP Logged)
Date: October 27, 2003 08:41PM

Several concerns I have with the use of gel formulations:

1)Lack of any controlled trials to give an idea of bioavailability...(ie. how much is absorbed). Thus the questions that are not answered with the use of gels are "what is the concentration that should be made?", "how much should be applied?", "where should the gel be applied?" and "does site of application make a difference in time to peak effect and percentage absorbed?".
2) Potential lack of consistency in manufacturing the gel. As a pharmacist, I greatly respect my professional colleagues, but there are no standards in place to ensure that one tube of gel will be of the same consistency and therefore efficacy as another. This could lead to tremendous variation in dosing.
3) Ethically, should a gel be used as a first-line approach when the oral route or another route is available that does have documented evidence of absorption? In other words, what if a patient has a symptom that needs to be managed and we use a route that does not have proven efficacy, and then lose valuable time in controlling that symptom? Is that ethically the best decision? Losing hours to days in managing a symptom can affect the patient's and family's ability to have valuable time together for closure. If the symptom could be managed with the same drug a similar drug via a route that has defined absorption, shouldn't that be our first choice? I have heard of many anecdotal reports regarding the value of a gel, but we must be careful not to let the anecdotal approach override the science of managing patients. If there is no other option, then perhaps a gel can be considered, but yet...we still must understand the pitfuls of this approach.
4) Cost...the gels often cost way more than oral or suppositories...often without a defined improvement in benefit.

I hope to see more evidence with the use of gels in the hospice patient, or at least studied in healthy adults so that we can make informed, ethical decisions on how to best use this approach. However, until we have such evidence, we must use caution in trying to based too much of what we do on a hope and a story.

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